THE BEST WIDER ROAD BIKE TIRE AND WHEEL SIZES

Feature photo rim and tire widths

One of the biggest shifts in road cycling in recent years has been the move to wider tires.  By spending less than $100/£70/€90 on a pair of 25mm wide or wider tires, many cyclists have been led to believe their comfort, speed and handling will immediately improve over what they experience on the 23mm wide tires that most of us have used for years.

Unfortunately, merely shifting to wider tires is a simplistic, incomplete or, depending on your set-up, partially or completely wrong way to improve your ride performance.  It’s not surprising that all of us busy and budget conscious road cycling enthusiasts would be attracted to a quick and cheap solution to better riding.  But unfortunately, it’s not that easy (or quick or cheap).

In this post, I’ll try to give you a more complete explanation of how wider tires and/or wider wheels can give you some or all of the better comfort, speed and/or handling you are looking for or make no difference or make things worse.

I’ll also try to do a few things that I haven’t seen in a lot of other articles that have addressed this topic.  First, using published tests and analysis where available, I’ll quantify the benefits and drawbacks that previously have only been claimed.  For example, exactly how much is rolling resistance reduced using wider tires and how much will it reduce your time over different distances?

Second, I’ll attempt to look at what the interrelated effects are of using a wider tire or wheel rather than looking at them in isolation.  For example, what effect does using a wider tire on a stock size wheel have on your handling?  Or, with the wheelset you bought to improve your speed, how wide a tire should you go with?

Finally, I’ll make all of this relevant to you, my fellow road cycling enthusiasts rather than than to cyclists in general or to triathletes, commuters, recreational, or gravel riders who do different speeds, distances, road surfaces and courses.

At the end of all of this, I’ll lay out my recommendations for the best combinations of wider tire and wheel sizes for road cycling enthusiasts based on your comfort, speed and/or handling priorities.

In a previous post I’ve reviewed the best road bike tires which covered standard and wider sized tires used by enthusiasts today.  After completing this post, I’ve written a review of wide alloy wheels that can bring you some of the ‘wider’ performance benefits on a reasonable budget, or at least a smaller one than what you might spend to get the full performance benefits of wide all-around carbon wheels that I previously reviewed here or aero wheels, reviewed here.

FIRST, SOME BASIC EXPLANATIONS OF WHEEL AND TIRE WIDTH

Most new road bikes with rim brakes today come with wheels that are designated 15C or are 15mm wide between the tire bead hooks that run along the inside of each rim.  These bikes are also generally specified with tires that are 23C or 23mm wide on their outside before inflation.  It may seem odd to call out the inside width of the wheel’s rim and the outside width of an uninflated tire but it will become clearer why later.

rim and tire widths

If you look at the bikes Bike Radar selected for their 2016 bike of the year awards, you’ll see that 3 out of the 4 rim brake bikes that were picked as the best in their price ranges are sold with 15C stock wheels while 2 come with 23C tires and the other 2 with 25C ones.  If you look at the 11 rim brake bikes that made up their £2,000 to £2,750 or US$2800 to $3800 category where many road cycling enthusiasts shop, 8 of those 11 bikes are equipped with 15C wheels and 8 with 25C tires.

As is the case with most new bikes, none of these wheels or tires are high performance or terribly comfortable, no matter their size.  Unfortunately, you don’t have the choice to switch them out for another set without an extra charge or for most, take delivery of the bike without any wheels and get the price reduced.

You’ll also see the same size 15C wheel rim widths on many rim brake alloy wheels that are sold as upgrades to the stock wheels.  This includes popular alloy upgrades including those I have recommended such as the Shimano Dura-Ace C24, Campagnolo Zonda and Fulcrum Racing 3 and also those in the popular Mavic Ksyrium line.  This will change for model year 2017 whees as all of these will come in 17C version.

Most popular carbon wheels have been sold in much wider rim widths for several years.

You’ll often see these widths referred to as 622x15C or just 15C on the wheel spec sheets and as 700x23C or just 23C on the tire boxes rather than or in addition to the mm sizes they refer to.  The first number is the rim or tire diameter which is the same for nearly all road bike wheels and the second one is the inside rim and outside tire widths, which vary.  The C designation is one set out by a cycling group called ETRTO (for European Tyre and Rim Technical Organization) that has worked with manufacturers to standardize around sizes.

The trend today is toward road cycling wheel rims that are 17C or wider and tires that are 25C or wider.  Starting mid-year 2015 and continuing in the 2016 model year Fulcrum, Campagnolo and Mavic have begun selling some 17mm wide upgrade rim brake wheels. By model year 2017, this transition should be complete.

Most new road bikes that have disc brakes come with 17C stock wheels and 25C tires.  As this “road disc bike” category is only a few years old, bike companies have made their frames wide enough to fit and deliver the benefits of these and even wider wheels and tires.

Whereas 15C wheel rims typically have an outside width of 19-21mm wide across their brake tracks, 17C rims typically run 21-23mm outside widths.  The widest alloy road rim brake and disc brake wheels run 19.5-21mm inside and 24-25mm outside.

The drawing below shows these rim width ranges and also the rim profile that often, though not always, accompany these widths.

Comparing Alloy Wheel Rim Widths and Profiles

About 10 years ago ETRTO recommended tire widths that would, in their view, safely fit each internal rim width or size (13C, 15C, 17C, 19C, etc.).  The concern was that a tire too wide for a rim could result in unsafe handling or a failure in the tire sidewall or rim.  On the other hand, a tire too narrow for a rim might disengage from the rim and cause a blowout.  While some companies, shops and riders still use the chart derived from these recommended combinations as if it were a sacred tablet (or perhaps a lawyer’s commandment), I hesitate to reproduce it here.

Why?  It doesn’t account well for the range of tire pressures, tire materials, tire bead designs, rim wall thicknesses, rim hook designs, riding speeds and probably a half dozen other factors including aero performance, rolling resistance, tubeless tires and modern designs of both rims and tires.

Many of the leading wheel design companies recommend tire widths narrower than the ETRTO ones to maximize aero performance.  These rim/tire width combinations run safely.  Mavic, on the other hand, seems to actively promote the width of the tires it sells with it wheels as adhering to the ETRTO recommendations at the expense of their aero performance.

WHY RIDE WIDER WHEELS AND TIRES

With that as background, what changes when you move to rims wider than 15C and tires wider than 23C?  It’s really three things – comfort, speed and handling – to varying degrees and not always in a good way depending on what combination of tire width, rim width and rim profile you choose.

Let’s take them one at a time and then together.

Comfort

With a wider rim or a wider tire or both, you don’t need to pressure your tires as high as with a narrower one to support your weight.  All things being equal (temperature, outside pressure, humidity, rim and bead design, tire model, just to name a few), you need the same amount of air to hold your weight up in the larger volume of the space created by the wider rim and/or tire as you do with narrower ones.  And we all know that riding at a lower pressure makes the ride more comfortable because the tires deflect more at lower pressures to absorb bumps and uneven road surfaces.  So if you have a wider rim and/or tire, you can ride more comfortably by lowering your tire pressure.

For years, ‘real’ roadies and racers used to blow up 20C and 23C wide tires to 110 to 120psi for what we foolishly thought and felt would make us go faster (less tire surface touching the road, more aero shape), our tailbones and soft tissue be damned.  Now it’s not uncommon for road cyclists to ride tube/tire combinations at 80 to 100psi (and tubeless or tubular ones even lower), all with wider rims and tires.  If you are doing a century, sportive, gran fondo or just riding irregular pavement on your long training or fun rides, lower pressure tires can make the ride a whole lot more enjoyable.

Why not just lower your pressures on whatever combination of rim and tire width you are running now to get more comfort?  You can do that to a degree (maybe 5-10psi), until the point where the tire loses the shape you need to handle well and you are more prone to getting a ‘pinch flat’ from squeezing your tube between the rim and tire bead (Type 1) while cornering.  Too low tire pressure can also cause the tube to pinch flat when you hit something straight on (Type 2) and there’s not enough air to prevent the tube from folding on itself.

Source: tubesaddle.com

Source: tubesaddle.com

No matter what width tire you are running, the key here is to find the right pressure to inflate your tire.  For that I suggest you start with a table provided by your tire company and a little trial and error of your own.  Tire companies vary quite a bit in what they recommend or even how specific they are willing to get as you can see in the examples for Zipp tires and Michelin ones on the left and right, respectively, below.  (Can’t even find one from Continental, maker of my recommended Grand Prix 4000S ii.)

Zipp and Michelin tire pressure recommendations

Zipp and Michelin tire pressure recommendations

I find it helpful to start with the tire company’s typically conservative recommendation and experiment by dropping the pressure in 5psi increments to find the level of comfort and handling performance that feels right for the speed, roads and bike handling I’m doing.

Putting a 25mm tire on many of the  15C stock wheels that come on new bikes is kind of like putting lipstick on a pig.  Many of these stock wheels aren’t terribly compliant or comfortable to start with. Putting an oversized tire on them softens the ride but doesn’t do anything to improve the speed or handling.

Of the alloy upgrade wheels I’ve recommended, the DA C24 is a very comfortable wheel with 23C rubber on it.  The other three are very stiff, good for heavier riders but harsh for those in the 160lb/73kg weight range and below. But there are a good number of alloy upgrade wheels in both 15C and 17C sizes that are compliant to start with and that you don’t need to run out and put wider tires on to make them comfortable.  There’s a table that compares comfort and other performance factors of alloy wheels in my post here.

Speed

The 1) tire’s rolling resistance, 2) wheel’s rim width and profile, and the 3) relationship between the rim and tire width all contribute to how much added speed you can get… or lose going with a wider tire and/or rim.  Again, let me break these three down.

Improved 1) rolling resistance, or the reduction in friction between the tire and the road, is often written about as a primary benefit of wider tires.  Tests by a range of independent sources I charted in my review of the best road bike tires (here) and those done by private testers hired by cycling publications show that, all else being equal, a wider tire will reduce your rolling resistance and therefore speed your ride.

But, the amount of rolling resistance reduction you get going from a 23C to a 25C to a 28C tire is only about a couple of watts combined for the front and back tires regardless of the tire, tester and test conditions.

Here’s a few of examples of the rolling resistance test results in watts for tires from the chart I mentioned above.

  • Continental GP4000S II tire, butyl tube, 17C wheel, 120psi, 18 mph/29 kmph, 70-73F/21-23C, conducted by Bicycle Rolling Resistance (report)
    • 23C = 25 watts; 25C = 24.4 watts; 28C = 23.2 watts or a 1.8 watt reduction
  • Continental GP4000S II tire, butyl tube, 109psi, 21 mph/35 kph, wheel size and temperature undefined, conducted by Tour Int (April 2014 Issue, subscription required)
    • 23C = 22 watts; 25C = 21 watts; 28C = 19 watts or a 3 watt reduction
  • Schwalbe One tire, butyl tube, 109psi, 21 mph/35 kph, wheel size and temperature undefined, conducted by Tour Int (April 2014 Issue, subscription required)
    • 23C = 24 watts; 25C = 25 watts; 28C = 26 watts or a 2 watt increase
  • Zipp Tangente Speed tire, latex tube, 15C wheel, 120psi, 18.6 mph/30 kph, 20C, conducted by Tom Anhalt (Crr Overall Spreadsheet)
    • 23C = 23 watts; 25C = 21 watts or a 2 watt reduction
  • Zipp Tangente Course tire, latex tube, 15C wheel, 120psi, 18.6 mph/30 kph, 20C, conducted by Tom Anhalt (Crr Overall Spreadsheet)
    • 23C = 25 watts; 25C = 24 watts or 1 watt reduction

I’m sorry, but a one or two watt rolling resistance difference spread over two tires going from a 23C to a 25C sized tire is not going to make any noticeable change in your speed or time unless you are riding a TT and care about a couple of seconds difference.  What will make far more difference is picking the brand and model tire with the lowest rolling resistance.  I selected some of the best to show above but the complete chart shows as much as 5 or 6 watt differences between the more popular clincher tires.  That could mean 15 seconds or so over the course of a 25 mile/ 40K road race and as much as a minute or more over the length of a century or sportive ride.

These tests are run with tires of different sizes inflated to the same pressure to get that one or two watts of reduced rolling resistance.  Of course, I wrote earlier about how you can lower the pressure with a wider tire to improve your comfort.  And comfort is why most roadies go to wider tires in the first place.  So what happens to rolling resistance when you reduce the pressure?

Mavic claims that you fully lose the rolling resistance benefit from the wider tire when you drop the pressure 20psi.  Tests from Bicycle Rolling Resistance (see here) on a wide range of tires shows that you lose a couple watts over two tires when you go from 100 to 80psi.

How much should you reduce the pressure when you go to a wider tire?

Look at the Michelin chart above a little closer and you’ll notice that for your given weight, they recommend dropping the pressure when you go from a 23C to a 25C tire by… wait for it… about 20psi.  Ugh.  Well at least you get a more comfortable ride at essentially the same rolling resistance from a wider tire.

So the claim of going any faster from reduced rolling resistance on a wider tire is, at best, false hope and at worst, uniformed hype.

By improving aerodynamic performance, a wheel’s 2) rim width and profile play a part in the speed you can get for the same amount of power output.

On one hand, a wider rim does put more frontal area into the wind by making any tire you mount to it wider and thereby increasing your aero drag when going straight into the wind.

On the other hand, some companies have shaped the profile of wider rims more than those making narrower ones in a way that reduces the amount of drag caused when you aren’t going into the wind.

And because you aren’t riding directly into nature’s wind, or what’s called the atmospheric wind, most of the time and you create your own apparent wind as you speed along, the effective wind is almost always coming at you from one side or another.  According to extensive field testing of road cyclists done by FLO Cycling (reported here), 80% of our riding time is spent with the effective wind coming at you from 0 to 10 degrees, 50% from 0 to 5 degrees, and only 11% of our time are we riding straight into a 0 degree effective wind.

Sptarting about 2010, HED and Zipp and other wheel makers since have demonstrated in tests of the wheels they’ve made that you can greatly reduce the drag of your wheels with a wider, deeper and U or toroid shaped rim versus those with narrower, shallower square shaped ones.

Look back at the drawing above comparing three alloy rim widths and profiles that range from the 15C, box section profile Mavic Open Pro shown on the left to to the toroid profile FLO 30 one on the right.

FLO had wind tunnel tests done to compare the Open Pro, the top, purple line in chart below against the FLO 30, the wheel represented by the red line.  Headed straight into the wind, the wider, toroid shaped FLO 30 has about 70 grams less drag, the equivalent of 9 watts.  At a wind direction of 10 degrees the reduction in drag improves to about 155 grams or 20 watts.  Over a 25 mile or 40K distance, that drag reduction will result in a 30 to 60 second time savings.  Over a century or sportive?  Well you’ll have time to grab another sandwich and still finish ahead of your buddies riding the narrower wheels.

FLO vs Open Pro Aero Data

 

I’m not saying that you can’t put a toroid profile on a 15C, shallow rim.  Let’s just say I don’t know of anyone doing it.  It may be harder to make and you’ll also get less of an arc out of a narrower, shallower rim than a wider, deeper one.

Likewise, few companies have put more rounded shapes on their 17C alloy wheels.  Indeed, some of the companies like Fulcrum and Campagnolo that have recently widened some of their alloy wheels from 15C to 17C haven’t changed the basic box shape profiles they’ve used on their rims for years.

It begs the question of whether the will is there or there is enough of an aero benefit going from a 15C to 17C rim even if you did add more shape to a box or V section profile.  The early and anecdotal comparisons of the speed benefits of this increase are inconclusive.

For example, Bicycling’s tech editor Matt Phillips had these immediate impressions (full review here) on riding Campagnolo’s wider Shamal Ultra wheelset:

I got to ride the C17 wheels for about two and a half hours at the launch of Campagnolo’s new Potenza group. For background, I’ve ridden the previous generation Shamal Ultra extensively, including immediately previous to this trip.

To be honest, I can’t say that a 2mm rim width increase made a significant, or even noticeable difference. Perhaps if I normalized everything else and rode the two wheels back to back, I’d pick something up, but in the test conditions I was given, I did not.

Though he doesn’t write about speed comparisons specifically, Velo News’ Dan Cavallari had this alternate view (full review here) after a similar first ride on the same model at the same press event:

Yes, it’s a bit against the grain to release an aluminum race wheelset in the era of carbon everything, but Campagnolo does not offer up the Shamal Ultra race wheels as a compromise. They’re light at 1,505 grams (2-way fit version; more on that below), stiff, and feature a wider rim than previous iterations of the Shamal.

And after a 40-mile ride in the mountains of Gran Canaria, we can honestly say we really like them. To write the Shamal off as just another aluminum wheelset would be a mistake because Campy certainly made an alloy wheel that’s not just good — it is competitive with the best carbon race wheels out there.

OK then.

The 3) relationship between the rim and tire width is the final consideration in determining how your speed can be affected by going wide.  Frankly, it’s the question readers ask me about more often than not.

Typically the question goes something like “can I put a 25mm tire on my XYZ wheel?” But, I’ve also heard questions like “my budget is x. what wheel would be best with a 25mm tire?”

That second question stopped me dead in my tracks the first time I read it.  When riders are choosing wheels that will cost 5 to 10 times that of the tire that they are basing their choice on, it really tells you how strongly some feel the push to get on the wide tire bandwagon that is rolling through the enthusiast peloton these days.

To the first question, I almost invariably answer that you don’t want anything wider than a 23C tire if you want to maximize speed.  If, however, you put comfort ahead of speed, go ahead with the 25C tire.

There are no wheels that I’m aware of where mounting 25C tires on the rims will make you faster or equally fast compared to that of narrower sized tires of the same model on the same rims.

Despite marginally improved rolling resistance even at the same inflation pressure, the aerodynamic relationship between the tire and rim has a far greater effect and favors the narrower tire.  I will try to explain why below but this drawing begins to give you a picture of what’s going on.

triathlete

Source: Triathlete magazine

Simply stated, air deflecting off a tire will continue at its exit or tangent angle.  If the rim is wider than the tire, some of the air will reattach to the rim and continue to flow along the rim until it detaches from the rim as it passes by.  If the rim is narrower than the tire, less of the air will reattach and more of it will be become turbulent as it passes by the rim.  The wider the rim is relative to the tire, the greater the amount of air that will reattach and the less the amount of turbulence.  The greater the distance between the air passing by the rim and the rim itself, the greater the amount of turbulence.  More turbulence creates more drag.

HED patented the relationship between the tire and rim widths including the angle of the rim where the air coming off the tire first reattaches.  This allows them to design wheels to excel across the range of yaw or effective wind direction the rider will likely see for the type of riding or event he or she is doing.  In the drawing shown taken from the patent application, you can see the central role of different tire widths (440’, 440”, 440”’) and its relationship to the rim angle (465) at the point where the air would reattach.

 

Source: HED cycling patent filing

Source: HED cycling patent filing

The toroid rim profile and rim length is covered by a patent that HED first developed and licensed to Zipp around 2009  that was central to the Zipps successful Firecrest line and caused other companies to move away from the box and V shaped profiles they had used for years.  While many leading wheel manufacturers have adopted angled brake tracks like those you see in these drawings, Specialized is the first company to license this newer HED patent.

So, as you can see, the relationship between the tire and rim’s width, along with the rim’s profile and depth, have a great effect on your wheel’s aerodynamics.  While the leading wheel designers including HED, Zipp, ENVE and Easton have their own design teams, all of these companies recommend you use tires narrower than the brake track width of their rims.

Most of the leading wheel companies designed their toroid shaped, carbon rims which have a 25mm or wider outside width around 23C tires.  Of course, as my review of the best road bike tire documents, many of the best 23C tires actually measure between 24mm and 25mm wide when mounted and inflated depending on the tire model and rim size it is mounted on.

In the case of Easton’s EC90 Aero 55, they recommend an even larger tire-rim width difference.  Easton’s 55mm deep Fantom wheel rim has a 19mm inside width, a 28mm outside width at the brake track and has a 29.5mm maximum width at the at top of the arc of its toroid shape.  As you can see in the chart below, 21C and 22C tires generally performed better in their aero tests compared to even 23C tires and certainly compared to tires of the brand and model.

Easton Fantom Tire Tests

Source: Easton Cycling

In the case of the same Zipp Tangente clincher tires used in these tests, the 21C bested the 23C version by 60 grams of drag which equates to 7.8 watts and 23 seconds savings over a 40K TT at 30mph/48kph.  (The time savings will actually increase if you don’t ride that fast.)

Of course, alloy wheels aren’t as wide, deep, rounded or angled at their brake tracks as the carbon wheels made by Easton and others are.  However, the findings that tires and rims work together to determine aerodynamic performance and favor tires narrower than rims are applicable to carbon or alloy wheels.

Handling

A wider tire and a wider rim together can provide better handling.  The wider tire provides a wider “contact patch” than on a narrower tire.  While the area of the tire patch for both tires is the same as long as your weight and the tire pressure is the same, that area spreads further across the width and less along the length of a wider tire.

The wider contact patch on a properly shaped and supported tire is what gives you better handling when road surface, moisture, tire inflation and speed are all the same.  While handling seems like a highly subjective property, Tour Int magazine – the highly analytical German cycling review publication – actually ran tests using a stunt rider to test and establish tire grip grades.  While the wider contact patch better handling claim makes sense and tracks with many enthusiasts experience including my own, I await quantitative evidence of how much better the handling is going from a 23C to 25C tire.

Continental use the handy (and frequently seen) chart below to show contact patch differences though, as discussed above, their headline conclusion about rolling resistance is technically correct but insignificantly small (and doesn’t warrant one, let alone two exclamation points) to the average roadie.

Conti contact patch chart

Now if you reduce your tire pressure on the wider tire to get more comfort, you’ll get a still wider contact patch than on the wider tire inflated to the same level as the narrower one.  So you’ll increase both the width and area of the contact patch relative to the narrower, more inflated tire you used to ride.  This is part of what improves handling.

The other part of the improved handling comes from a wider rim.  The wider rim sets the foundation for the wider tire to better keep its shape as you can see in the drawing on the left.

 

wide-rim-drawing

The problem comes when riders, having read about all the benefits of wider tires, mount a pair of them on the 15C wide alloy stock wheels that came with most of our new bikes or the upgrade alloy wheels sold by most of the leading wheel makers for the last 3-5 years.  A 25C tire on a 15C wheel can feel squishy, even more so if you’ve reduced the air pressure to get more comfort.  This squishy feel is a symptom of the tire losing its shape and its tendency to fold back on itself.  This is the opposite of the improved handling you are looking for by going to a wider tire.

In the worst circumstances, a tire that’s too wide for its rim can experience a Type 1 pinch flat when you are cornering at speed as shown an earlier drawing or the tire bead can pull away from the rim hook, also resulting in a flat.  Not good, to say the least.

PERFORMANCE FROM DIFFERENT TIRE-WHEEL WIDTH COMBINATIONS

So what combination of tire and rim widths are best for you, my fellow road cycling enthusiast?

The tire-rim width chart in the ETRTO standards manual says a 15C rim can safely use tires from 23C all the way up to 32C or mm in width.  If you look closely, it also says that you should use nothing narrower than a 28C tire on a 19C rim and a 35C tire on a 21C rim.  ENVE, Bontrager, and Easton make 19C road rim brake clinchers and HED and Zipp both make 21C ones and none of them are recommending tires that wide on their wheels.

The ETRTO standards say nothing about the speed, road surface, tire type or tire pressure conditions you are riding under.  A mountain biker bouncing along on knobby tires inflated to 40-50psi on a dirt trail going at half the speed of a roadie leaning into a fast corner on a smooth road with tires pumped up to 80-100 psi are experiencing very different situations.  And it hasn’t been updated as road wheels have gone through a couple generations of major change.

In my humble opinion, the chart is a guide that needs to be updated or tossed when considering the real world that road cycling enthusiasts live in today.

Instead, here’s my take on what mix of comfort, speed and handling you can expect with different tire-rim combinations.

A 23C tire on a 15C wheel – this is the likely stock or alloy upgrade wheel and tire combination you have as a baseline. You know how this rides. What follows are your options.

A 25C tire on a 15C wheel – somewhat improved comfort over a 23C tire but worsened speed and handling.  Better to reduce pressure 5psi or so on 23C tire for better comfort without losing handling performance.  Neither combination is going to be an aero star.

A 25C tire on a 17C wheel – better comfort but no better speed or handling than a 23C tire on a 15C wheel.  23C tire on 17C wheel at right pressure will get you somewhat improved comfort with improved aero if the rim has at least a rounded nose rather than box or V profile.

A 25C tire on 19C or wider wheel – best comfort, improved speed and handling over options above. A nice set-up for long endurance rides at a good average speed (18mph/29kph or higher)

A 23C tire on a 19C or wider wheel – best speed and handling combination. If you’ve chosen this set-up, crits and road races are probably high on your list and comfort further down your list of what matters though there are plenty of wheelsets in this width that will be plenty comfortable to start without the need of a wider tire.

* * * * *

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117 comments

  • Really, really great article. Clear and very in-depth. I’m building a front wheel for my TT bike and wondered about tyre choice. Got a rim which is 88mm deep and 26.5mm at brake track. Wondered if the narrower tyre is a good idea for tubulars as well as clinchers. 22mm too narrow?

    • Adam, Hard to say. Depends on the rim profile/shape. I don’t have any experience with wheels that deep. The 55mm deep/28mm wide Fantom rim-tire widths tests shows Reynolds has found narrower is better, at least for drag reduction. Steve

  • Building up a set of wheels that are 19C (28mm at the brake tracks) and considering my tire choices. If I’m reading your analysis correct, the difference between a 23mm tire and a 25mm tire on these wheels is splitting hairs. Sounds like I can’t go wrong either way. What are your thoughts on 23 in the front and 25 in the rear? Sounds like this might be a best of both worlds approach. Get the aero and weight benefit of the 23 in front while giving a little extra comfort in the back where most body weight is and the airflow is already pretty tubulent.

  • Hey there. I just got my hands on some HED Jet 6 Plus wheels. Great deal on CC during their daily Tour de France sales. They measure 25mm external width and 20.7mm internal. What would be the ideal tire to throw on? 23mm? I need to set them up and make sure they work on my bike. Hope they do.

  • Hi Steve,

    Got this from the road.cc website: “Most teams are using wider tyres with 24 and 25mm being the most common sizes. A lot of teams using Continental 25mm tyres and those on Specialized use 24mm width tyres. The Trek team told us that every rider is on 25mm tyres for all road stages, only going narrower on time trial bikes where aero concerns still matter.”

    Whereas, you say: “A 23C tire on a 19C or wider wheel – best speed and handling combination. If you’ve chosen this set-up, crits and road races are probably high on your list and comfort further down your list of what matters though there are plenty of wheelsets in this width that will be plenty comfortable to start without the need of a wider tire.”

    Ofcourse the pros want to go fast and that’s their main concern. Why do you think are they using 25C tires contrary to what you say on the compromises with speed?

    Cheers

    Ragtag

    • Ragtag,

      A few thoughts in response to your comment:

      I don’t know what sources road.cc is using for the report you are referring to and how well researched the reports are. Terms like “most teams” or “a lot of teams” or “The Trek team told us” sound a bit inexact for my liking. I likewise write in rather inexact terms from time to time as in the excerpt you’ve shared above but I’m providing my opinion/recommendation for a specific segment of riders that I write for (road cycling enthusiasts) based on conclusions I’ve reached after my own evaluation and from researching the work of others rather than feeding back what a few people may have said anecdotally. I’m writing a blog or a column with my analysis and recommendations whereas what it looks like road.cc is doing (from what I can take from what you’ve quoted) is presenting their information as factual reporting (from sources I’m not aware of).

      But, lets assume that everything from road.cc is accurate for the moment. Consider this.

      Pros use tubulars. Tubulars mounted and inflated run pretty close in actual width to the “C” designations. So a 23C or 25C tubular is going to be 23mm or 25mm +/- a couple tenths. For more, see Tom Anhalt’s chart here https://docs.google.com/spreadsheets/d/1C37Wq7d6d1Chig_ClcbsWuG8ugTxKLEmvAajTD9tcU0/edit#gid=1224624714.

      Most enthusiasts use clincher tires rather than tubulars. Many, perhaps most enthusiasts that also race in CAT 3 and less competitive amateur races also use clincher tires. Those enthusiasts are the ones I write and make recommendations for. Many clinchers run up to couple mm (rather than tenths) wider than their C designations. Popular, low rolling resistance 23C clinchers like the Conti GP4K2 run 24.2mm to 25mm wide. So using a 23C actually gets you a tire closer to 25mm than 23mm wide tire. A 25C version of the same model tire runs 27mm wide. Specialized S-Works Turbo 24C runs 25.5mm. So if you want to ride a 25mm tire in one of those brands, you want to buy the 23C or 24C versions. I mention those two because they are two training tires with the lowest rolling resistance among training clincher tires and because those brands are mentioned in your comment above even though they are very likely referring to tubular tires from those brands.

      This variance to the C designation or the stated mm width on the box varies by brand and even sizes within brands. Michelin’s Pro4 Service Course and Pro4 Comp clinchers, a couple more popular tires despite their poorer rolling resistance relative to the Conti and Spech I’ve mentioned in the paragraph immediately above run pretty close to the 23mm suggested by their 23C designation but their 25C Service Course runs 28mm. Mich has introduced new clinchers now so let’s hope RR and widths are better. The Zipp Tangente Course 23C runs 23.8mm but their 25C actually runs narrower by a couple tenths (24.7mm). Same goes for their Tangente Speed race tires. So if you are a planning to use Zipp tires, there you go.

      All of this is laid out in great detail and for more clincher tire brands and models in my post here: https://intheknowcycling.com/2015/05/28/best-road-bike-tires/#Rolling

      There is further variance depending the inside width or your rim and the pressure you are inflating your tire to. And tires widen with use and when you ride to higher altitude, low pressure environments. I haven’t seen conclusive research on the amount of change these further variables create but I’m pretty confident in saying that each one of them will further widen your tire to some degree when you are on the road.

      Putting this all together and all the other things I’ve laid out in the post above, I conclude that most 23C clincher tires are going to end up closer to 25mm which is the external brake track width of most 19C wheels I’ve reviewed lately. See https://intheknowcycling.com/2016/05/03/best-road-bike-wheel-upgrades/#Wide. Some 17C and 19C wheels have wider external widths, yes (https://intheknowcycling.com/2015/05/01/best-all-around-road-bike-wheels-2015/#Reviews), but most people buying those wheels want top aero performance on what is already a pretty comfortable wheel with a 23C/24.5mm to 25mm wide tire.

      All of this further demonstrates a few things I learned a long time ago. 1) Sweeping statements about what the pros are said to be doing (even if well reported) don’t always (or even usually) apply to the decisions we should make as enthusiasts. More broadly 2) Don’t always believe what you hear or read (including from me) and, 3) Reach your own conclusions.

      Steve

  • Heya Steve, nice article!

    Now now now, I am a bit confused now, I heard Pros in Tour/World Tour or top race go 25c tires set but what the point if 23c with wider rim get the best speed?

    25c on wide rim would be the best comfort of course but those Pros and Speed freak will probably preferred speed over comfort in the begin with, no? yet why they still choose to go with 25c?

    As your article mentioned above, a 23c tire on 19c rim will be the best speed and handling combination and to be note, the wide rim design usually give enough comfort already so no need to go 25c tires, no?

  • Steve. Just got to your site recently and love the stuff. Been riding only 4 years and at age 60 (very soon) I’m looking for all the help I can get. Ride with a group in SW Fl (Naples) that splits between 18-22 and 22+. I’m in the b group. Just bought a Specialized Roubaix, SL with the Ud12 that you reviewed. Came with 26c tires. Although I was not thrilled with the 105 brakes, and cassette, I figured I could upgrade those as I wanted the electronic shifting. I’m more into endurance rides than speed, but certainly would like to increase my mph a bit. I’m looking at upgrading my wheel set and am intrigued by the combination of wider wheels and wider rims (25/19) you suggested that mirrors my riding style. Keeping the price below 1500 (US), what wheels have the 19 mm internals that would give me the best speed/comfort result. Thanks a bunch and kee up the great work.

  • Truly impressive article which must have taken a long time to write. Showed it to my son who has been building wheels for CF in Rio and he couldn’t fault it although professional pride encouraged a few minor and esoteric topics that he felt he might have include. But he wouldn’t have ever had the time to write it…..!

  • Hey Steve
    After reading your articles over and over and the links provided with more reviews and tech info I finally made my purchase and upgraded my wheels. You didn’t actually review the wheel set I bought, the Boyd Altamont 30mm deep alloy clincher with 19.89mm internal rim width. However it was the inclusion of the Boyd Altamont Lite in your Wider Alloy Clincher review that got me investigating the wheel range further and your informative articles that enabled me to make this decision. I’ve only rode on a couple of sets of stock wheels as supplied on bikes from new until now and am extremely pleased with my upgrade. I am running the Conti GP II’s 23c on these and am experiencing all the benefits you have mentioned above and can still go wider if road conditions or type of rides require it. These wheels have all the specs that on paper give them the ability to give the best performance and advantages in all area’s and are a brilliant all round wheel set which are leaders in design and a high quaulity built product. Even with small increments of speed, comfort, handling and aero advantages they still all add to improved performance and aren’t negatives or compromises. For the enthusiast cyclist this wheel spec ticks all the boxes so thank you Steve for leading me down the road to them.
    Always very interesting and informative reading throughout your site Steve, great work.

    Andrew

  • Thanks Steve for this article!

    I’m using wider (32C) supple-sidewall tires for touring. Wheel air resistance isn’t a big deal at my speeds but I’m concerned about handling and safety. The charts I’ve seen list rim ranges for a 32C tire ranging from 15C to 19C, which seem narrow to me if you can run a 23C tire on a 19C rim. Can you offer some advice about the consequences of moving to a much wider (24C or 25C) rim?

    Thanks again!

    • Stuart, I’m afraid I’m not very knowledgeable about wheels of that width. Best to check with someone knowledgeable about touring or MTB wheels. Steve

  • Hi Steve,

    I have gone through your article as well as the one on the 105% rule. (The Rule of 105 states that the rim must be at least 105% the width of the tire if you have any chance of re-capturing airflow from the tire and controlling it or smoothing it.)

    I am about to receive me dream wheels, the Enve SES 4.5. I am deciding what tires to use, and am comparing a lot of them for various criteria. A difficult decision is the tire width, as the two rims, front and back, are different. Here are the specs for the front and back wheel:

    Depth:48 / 56
    Internal Rim Width: 18.5 / 17
    External Rim Width: 27 / 25.5

    Enve themselves are not decisive; they suggest using either a 23 or 25 mm tire. See: http://enve.com/products/ses-4-5/

    You have written elsewhere (“how to ride faster”):

    “I don’t know about you, but it seems a bit crazy to me to buy a new set of wheels and then put a tire on it that promptly defeats some of the aero benefits you just spent good money on. From what I’ve learned doing the research for this article, my approach going forward is to pick a few tires with the lowest rolling resistance I can afford and then select the one whose actual width is as close to the brake track width of the rims I’m riding (or front rim if the rim widths are different). If I’m in more of comfort than speed mood on a given day, I can lower the tire pressure a little. I can always pump it up on days I’m targeting more speed.”

    But here you write: “ A 23C tire on a 19C or wider wheel – best speed and handling combination. ”

    This Enve SES 4.5 wheelset would be a great one for applying all the insights!

    Optimizing speed (aerodynamics), what would be the best tire width? (by tire width I mean the actual width, not the specified width as tires are usually wider than specified). here’s a simplified consideration:
    These are wide rims, so 25 both front and rear? But wait; the front rim is wider than the rear, so: 25 for the front, and 23 for the rear? But to match the rim widths better, use 27 for the front , 25 for the rear? But wait, 23 both front and rear might still be better aerodynamically as the results on the ?
    Or 23 in the front and 25 in the rear (for more comfort), despite the fact that the front rim is wider than the rear rim.

    I would love to hear your remarks.
    very best, Michael

    • Michael,

      Wow, thanks for reading so closely and thinking about it from so many different angles. I much prefer people do this than just slap on a 25C tire because that seems to be what everyone else is doing.

      As for this wheelset specifically, there’s one more post that I’ve written that you might want to read (here) that reviews this wheelset and answers the tire question you pose. First, I used the Conti GP4KSII tires for best rolling resistance. I tried various combinations of 23C and 25C tires. The most aero would be to use the 23C on both. The most comfortable was the 25C on both. I ended up putting a 25C on the front and 23C on the back to get a combination of aero and comfort with too big a hit aerodynamically. Lastly, I ran it at 80psi front and 85psi back for best comfort. That probably is more of a mish mash solution optimizing neither. The 25C measured 26.75mm on the front which is about a half mm wider than the brake track width but less than the 27.1mm I measured for the brake track width. The 23C on the back measured 24.5mm which is about the same as the 24.7mm brake track width I measured and less than 26.0mm max width I measured. The back wheel aero is less “pure” as you compromise a good deal of the aero with your your feet rotating through the air stream and of course the seat tube and chain stays having whatever effect they are having.

      Bottom line, you’d probably be best off with 23C on both to maximize aero if you are looking for speed and 25C on both to maximize comfort. You will get some rolling resistance benefit going with the 25C over the 23C but it would be outweighed by the aero benefit, at least on the front of the 23C.

      Not an exact science… to say the least and many other factors coming into play as you read in the How to Ride Faster posts that collectively can have much bigger effects if you get them right. Steve

      • Hi Steve,

        Thanks for your quick reply, and sharing the relevant experience.

        Here’s my list of factors to consider when buying a set of clincher tires:

        (1) Constant factors, easily determinable:

        a) cost
        b) weight

        Comment on a): But if you’re willing to spend a few thousend dollars on wheels, then the 20 to 30 dollar difference between tires should make no difference.

        Comment on b): I believe weight issues (40 to 50 gram differences) will be outperformed by the other criteria below. So this should not be an important factor. Furthermore the difference in weight between the various tires when compared to the total weight at the outside of the wheel (rim+tire) is not so relevant.

        (2) Factors influenced by compound, carcass, make up of the tire (puncture resistant layers, etc.), inflation pressure, tire width, and choice of rim (width of rim and angled or flat brake track). Not easily determinable, serious testing is needed.

        c) grip (dry, as well as in the wet)
        d) durability
        e) puncture resistance
        f) comfort (mostly the combination of tire width and inflation pressure)
        g) handling
        h) speed
        -rolling resistance
        -aerodynamics (taken together with the chosen rim)

        —> Any comments welcome on this list!
        —> Let’s go back to the topic of my original question: tire and rim width as related to criteria f, g, and h (mostly setting aside rolling resistance). Thanks for the info on the SES 4.5 wheelset, but now I want to take this more general.

        This what I take from your writing:

        – more comfort requires wider tires and lower inflation pressure, but not too low because rolling resistance goes up and handling goes down. And not too wide as you loose aerodynamics and increase drag.
        – good handling suggests wider tires but not very much wider than the rim width, the handling then goes down.
        – reducing aerodynamic drag requires good alignment between wheel and tire width. Remember the 105% rule. It states that the rim must be at least 105% the width of the tire if you have any chance of re-capturing airflow from the tire and controlling it or smoothing it.

        Thus the 105% rule sets the maximum tire width for any given rim width as far as aerodynamics goes.
        Here’s my next question: what is the minimum tire width needed for a specific rim width? You suggest that 23C on the ENVE front rim (27 mm wide rim) is best from an aerodynamic perspective, but perhaps that is too narrow? What if I put a 22C or 20C tire on this rim? At some point the aeroodynamics must go down again, isn’t it?

        Shouldnt there be a 105%-125% rule or something like that. The rule would then be: the rim must be at least 105% and at most 125 % of the tire width for best aerodynamics.

        My second question is related to the first. You write:

        “Of course, alloy wheels aren’t as wide, deep, rounded or angled at their brake tracks as the carbon wheels made by Easton and others are. However, the findings that tires and rims work together to determine aerodynamic performance and favor tires narrower than rims are applicable to carbon or alloy wheels.”

        So for example the Shimano Dura Ace 9000 C35 clincher has a width of 20.8 mm. When we apply the 105 rule, shouldn’t we then use 20mm tires on these? And not 23C?

        • Michael, I love your passion but I’m not sure I can answer every question in detail. If you haven’t already, take a look at my posts on tires and aero wheels. I cover some of this there. Remember the 105% rule isn’t a rule per se, it’s a good directional guideline from one smart, experienced industry engineer for those who want every last gram of drag removed from their wheelset that’s consistent with what I’ve come to learn over the last few years. Other smart, experienced guys may have different views and most enthusiasts aren’t going for every last gram of drag reduction. Easton’s tire chart in the aero wheel post suggests the bigger the difference the better for their wheels. Other guys who sell wide tires and are good at getting publicity are coming up with data that says wide tires are faster (shocker) and don’t take wheel width into consideration. 20 and 21mm tires on 15C wheels are the most aero but then most 15C road wheels made today aren’t very aero any more. There’s lots of other ways to improve your aero performance and speed a lot more than these differences that I go through in my posts on how to ride faster. Thanks for your energy! Steve

  • Hey Steve,

    I don’t do centuries so often, but I do (and train for) a lot of hill-climbs which could be anywhere from 1 – 3 hours at a time. I’m also a light rider, at 68kg’s. So, comfort is not as much of a concern as 1) climbing efficiency and 2) handling on the descent.

    With that said, given you mention that “a 25C tire on a 17C wheel – better comfort but no better speed or handling than a 23C tire on a 15C wheel”. Is this a typo…? I ask because everything else you’ve written seems to suggest the 17c/25mm combination will handle better than the 15c/23mm combination…

    If not a typo, I might actually go with the older 15c Shamal’s with 23mm rubber over the newer 17c Shamal’s with 25mm rubber. The 15c Shamal’s are lighter and almost $500 cheaper too at the moment, both of which are a bonus!

    Cheers,

    • robertbb, not a typo. depending on the tire you use, you are going to get about the same amount of tire overlapping the exterior width of the rim. Steve

      • Thanks Steve,
        In terms of tyre to rim interface, this makes sense. What I still don’t get is how a 23mm conti GP4kS2 on the C15 will handle descents comparably with a 25mm conti GP4kS2 on the C17, given the reduced rubber contacting the road. Are you saying the difference in contact patch is, more or less, negligible?

        • In terms of handling, it’s not so much about how much rubber is contacting the road as it is the shape of the rubber (light bulb round vs. straight sidewalls) and how good your handling skills are. The tire shape is determined by the amount of overhang of the tire over the rim, which in the two cases is about the same. With a 25C Conti GP4KIIS tire on a 17C rim (mounted, inflated to 100 psi), the tire measures about 27mm wide with about 3mm of tire overhang vs a 23C on a 15C which measures 24.0mm, 3.5mm. So negligible (0.5mm) overhang/tire shape difference. If you want better handling, the better choice would be to get a tire that measures truer to the 23C or 25C size but has as good rolling resistance as the Conti. The Zipp Tangente Speed tires have similar RR but mounted/inflated measure closer to their C width but cost a good deal more. The old Michelin Pro4s were right on their C width but had horrible RR. Michelin is saying their new tires have competitive RR but I haven’t seen independent tests yet.

          So, more comfort but no better speed (1 watt better RR for the same model 25C vs 23C at aero speeds) or handling (see above). That said, if you want the 17C/25C combination, go with the Zonda C17 which has the same rim and spoke pattern/bracing as the Shamal without the meaningless hub shell differences and other added bells and whistles that add price but not performance. You’ll save yourself a boatload of money. See here and here for the best prices from dealers with great customer satisfaction performance. Steve

          • Thanks again Steve, very detailed response and it all makes sense in the context of 23mm/15C vs 25mm/17C. One variation not discussed in your post (or the comments so far) is 23mm/17C. On the new Campagnolo rim (applies to both Shamal and Zonda) the outside width is 22.5mm (the C15 was 20.5mm). Perhaps when run with 23mm Continental GP4000S2’s the resulting overhang will be better than the 3mm and 3.5mm overhangs you mentioned above with 23mm/15C and 25mm/17C). What are your thoughts?

  • 23C tire on a 17C wheelset will give the best speed and handling combination.

    • Interestingly, in the calculations you offered above:
      – An inflated 25mm Conti GP4KS2 tire on a 17C rim measures about 27mm wide. The 17C Shamal is 22.5mm wide, so the overlap is actually 4.5.
      – An inflated 23mm Conti GP4KS2 tire on a 15C rim measures about 24.0mm wide. The 15C Shamal is 20.5mm wide, so the overlap is 3.5.
      So with the above combinations, assuming the inflated widths are accurate, there is actually less overlap (and therefore a better handling and more aero setup) using the older Shamal’s with the narrow tyre – given the negligible RR difference.
      Would you happen to know the actual measurement of what a 23mm Conti GP4KS2 tire inflates to on a 17 rim? To trump the above, the overlap would need to be less than 3.5… would be very interested to know.
      Cheers!

      • robertbb, We’re getting way down in the weeds now. As I said at the top, it’s more about the tire shape and handling skills. As I said in the post itself, you should consider the potential tradeoffs of comfort, aero and handling. As I’ve written in my Best Road Bike Tires post, different tires of the same “C” size measure differently and rolling resistance varies. In addition, tire/wheel interfaces, road surface, inflation level, tire construction, rim and bead construction, rim height, wheel stiffness, and probably a handful of other things all affect handling.

        To answer your question, a 23C tire on a 17C rim will have less overlap than a 25C on a 17C or a 23C on a 15C. But as to what I understood to be one of your two original concerns – “handling on the descent” – and to your question about whether to buy the 15C or 17C version of the Shamal, my recommendation is to buy the Zonda C17 and put a 23C GP4KSII set of tires on it filled to about 80psi for your weight. OK?

        Enjoy your ride,

        Steve

        • Hey Steve,
          I went with your recommendation… almost 😉 I chose the C17 rim but opted for Shamals (treated myself by putting down the extra few hundred for the better hubs/bearings and spokes). The set came in at 1475grams on the dot (Rear Wheel: 833g, Front wheel: 643g). I mounted 23mm GP4KSII tyres and am using Michelin Aircomp Ultralight Latex tubes and inflate to 85PSI (have found that over the course of a decent ride, I can lose 3 or so PSI…). The tyre mates to the rim very, very well and while I don’t have a tool to measure exactly what the overhang is it can’t be more than 1mm on either side. This combination absolutely flys. I am finding I am going quicker with less effort on the flats, and hills on a route I’ve been riding for 15 years feel “smaller”. I’m not sure whether to put this down to rolling resistance or stiffness, but it can’t be weight – my old wheelset was 135 grams lighter. As to handling, I’ve never experienced anything like it. I’ve driven out to one particular climb I know well with a good selection of twists, turns and hairpins and brought both wheels with me. My old wheels feel as floppy as fettucini underneath me… my new wheels are made by people who eat it 😉
          Cheers.

          • I just bought the new campagnolo shamal mille 17c. But i’ve not choice the right tires yet. From your experiment i’ll try that combination mounted 23mm tire on my shamal. Hopefully it will be the best combination. Anyway i just thought to buy Challenge tire (Elite Pro open tubular), so it could be good?

  • Hi Steve,

    Quick questions:

    If I have a 23mm GP4KSII on a 17c rim which is 25 mm wide (Eg on a reynolds assault) If the tyre blows out slightly wider than the rim (eg 25.1 mm or something like that) do I lose all the aero gains?

    Thanks!

    • Wells, From the research I’ve seen, generally you want your tire to be slightly narrower (about 1mm narrower on a 25mm wheelset). But it’s not all or nothing. Yaw angle, rim shape, tire sidewall shape, rim brake treatment (and probably a few other things I don’t know about or are proprietary technology) also affect how much more aero drag a wheelset will show in a wind tunnel.

      FYI, as far as the combination you mentioned, I measured the 23 Conti GP4KIIS tire at 100 psi at 24.3mm wide, the Reynolds Assault SLG inside bead width at 17.5mm and the external ave brake width at 24.8mm. Steve

  • The Michelin power comp clincher seems to have a very low rolling resistance and the 23 version measures 24mm on a 15C rim, can this be the perfect tire to mount on a 25mm rim?

    p.s. Is it just me or your articles are not dated? I never know if I’m looking at a recent article or something from a few years ago.

    • Hi Manuel. I haven’t seen any testing reported about the Power Comp tires yet other than what Michelin has said. Can you refer me to anything you’ve seen? Thanks.

      Regarding article dates, you can always find the original post date in the HTML address. That said, I update them regularly after I review new products (e.g. the new Mavic Cosmic Pro Carbon SLC) or get new information, when products have been discontinued or are no longer widely available (e.g. Roval CLX40 and soon the Michelin Pro4 series) and update links to stores that have gear I recommend (weekly) or review (monthly). I’ll also update them when I learning something new about the category in general or about some I learn from a reader (e.g. you about the Michelin tires) or when something significant is published or announced (e.g. the new Shimano C40 wheels, announced specs (which were announced wrong and the corrected ones brought to my attention by a reader) and dhen they’ll be available ). I also write a post every month or so to tell people who’ve signed up for e-mail updates, facebook, twitter or RSS feeds what new reviews I’ve done and what is coming. I won’t claim that my updating practices are as timely as I’d like for some of the lesser read posts. My bias is to get new posts and reviews out. Cheers, Steve

  • Hi Steve, have enjoyed all your articles on wheels & tyres, thanks very much for taking the time to write them and answer comments like you do. I’m about to purchase a new road bike with disc brakes and wider clearances and your articles have given me pause for thought. I’m wondering though, given that wider rim/tyre combinations seem superior to conventional narrow rim/tyre combinations, why stop at 25C tyres with 19C rims?

    Most of the riding I do is solitary or in a small group, over long distances, poor road surfaces with plentiful potholes & some occasional hard gravel or packed earth sections. I tend to average around 17mph, maybe slightly higher in a group. At this speed, I have assumed that aerodynamics is not particularly important and that I have more to gain from the increased comfort and handling of wider tyres. My thinking is that the suspension-like effect of a wider tyre will keep me feeling fresher and therefore improve my power output, especially towards the end of a long ride, by more than the power I will lose to aerodynamic drag.

    To this end I have been thinking about buying a Syntace W30 rim to fit to the CK hubs I already have. This is a 25C rim with a 30 mm outer width. The Syntace rims are heavy and box-section but I could then use a 28C tyre without overhang.

    What do you think, is there any downside compared to a similar (box-section) narrower rim/tyre combination? Or would I be better off with deep-section 19C carbon rims and 25C tyres for the sort of riding I’m doing?

    • Nathan, It kind of looks like you are plan to do more rough/dirt/gravel road riding than regular/occasional bad section road riding. If it’s the former, perhaps a wheel like you describe would work better. I really don’t know those kind of wheels but my guess it’d be pretty heavy and slow on regular roads. Steve

  • Hello Steve,

    Thanks for beating this subject to death, for all of us. My question concerns what tires to put on 15c rims. You suggest that wider rims improve handling because they allow the tire to better retain their shapes during lateral stress. But where is the cut off? When is a rim too wide for a tire?

    Also, I have personally found that going to 25 mm tires have improved my cornering confidence, and I’ve always attributed this to the more solid contact patch of the 25 mm tires vs the 23 mm tires. I run 15c aluminum rims, and the 25 mm contis (or I guess more like 27mm) makes it feel like I have more rubber on the road, than when I have 23 mm tires on. I weigh around 160 lbs, and I would try to pump 110 psig in to the 23’s, and around 105 into the 25’s. the 25’s also definitely feel smoother, maybe that’s the reason.. Is it all in my head, or are we missing something here?

    • yonguo90, As I’ve written, I recommend no more than 23C tires for 15C rims. One thing that may be affecting your handling is your pressure levels. At your weight, you’ll have better handling (and comfort) in the 90 to 100 psi range. Lowering the pressure is kind of like increasing the tire width without affecting your aero properties. I used to ride in the 110 range as a 150lb rider and have my 23C inflation down to about 90 and 25C around 85. Steve

      • Steve,

        So If I were to compare a 95 psi 23 tire, and a 100 psi 25 tire on a 15c rim, such that their comfort and stability are matched, which one would handle better? wouldn’t lowering the pressure also worsen the handling, as it increases deflection of the tire during a corner?

        Also, out of curiosity, how did you make the determination that 25 mm would experience more deflection than 23 on a 15c rim, such that handling is compromised? I’ve always thought that this would only be a problem for crazy wide tires, like 32 on a 15c rim or something. Is it based on qualitative tests, or is there some math to it?

        I realize most of your discussion is directed at wider rims, which makes sense from a performance point of view. But as a grad school student, I can’t find the justification to spend $600+ on a set of carbon wheels for 10-20W of savings that I’ll only find helpful occasionally.

        • yonguo90, I’m no longer a grad student but with a family to support, I’m probably in a similar boat, though a bit downriver, when it comes to spending wisely.

          Not to get all theoretical and technical, there’s probably a bit of science and a bit of art involved here. Let’s say that a 25mm tire is 2mm wider than a 23mm one on the same 15C rim. It could be more or less depending on the tire maker and model and if you are putting the same two make and model tires on a 17C rim but let’s just take the 2mm as a starting point.

          From measuring a lot of tires at different pressures, I’ve found varying the dropping the pressure 10 psi for 23mm or 25mm tires increases the width by about 0.5 mm. So, increasing the tire size has a bigger effect on widening the tire than lowering the pressure in the range you would expect to change it.

          The other part of this is experiential. You know the feeling when you haven’t been out for a few days or the temperature has dropped a little and you forget to inflate your tires. You get out there and they feel mushy. You can tell. Well if you experiment with changing your pressure 5 psi from one day to the next, you’ll feel the spectrum where the handling suffers if it is inflated too low to where the ride is harsh and the handling isn’t confident when it is overinflated. Somewhere in between is where you want to be.

          I can tell you from my experience as a rider about 10 lbs lighter than you but can’t likely describe why to a grad student’s satisfaction that a 95psi 23C tire on a 15C rim is going to be more comfortable and handle better than a 100psi 25C tire on that same rim. The narrower tire will run squarer in the 15C beads with less deflection. The 25C tire will want to deflect more but at 100psi it will be more rounded or light-bulb like than the 23C at 95psi and not give as much making the cornering harder. It just gets worse the wider the tire or when you get too low a level of inflation with the same narrow rim.

          Also, a lot of this wider tire, lower inflation talk is about comfort and rolling resistance. But, you can put the most supple 25C tire on some rims at a very forgiving low pressure like 80psi and the ride will not be comfortable. Same goes the other way. Put a 23C tire at a standard 90-100psi on another rim and you’ll get a very comfortable ride. And the rolling resistance changes maybe 1 watt per 5 psi difference on the same tire. With different tires the rolling resistance difference can be 6-10 watts, more if you are comparing rugged tires like Gatorskins to normal training tires like Grand Prix 4000. You also can get big watt differences with the profile of the wheels. Point is that it’s not just about the tire, width, and pressure. The wheelset has a lot to do with it. You can’t make a harsh wheel comfortable with a wider, less inflated tire. And you can’t make a slow wheelset fast by putting on wider tires.

          You can control the rim profile and wheelset comfort with carbon materials in a way you can’t with aluminum alloy. That’s the attraction of carbon rims.

          Steve

  • Excellent article that cuts through a lot of the marketing nonsense at the moment.
    What do you think of GCN’s recent video ; https://www.youtube.com/watch?v=yrHxQg1OW0A&t=2s where they are loving 30mm wide tyres (on very wide ENVE rims).
    According to them it is a ‘game-changer’.
    Having been on 23’s (Lightweight tubulars) for the last 8/9 years, I am now starting to experiment with 25’s, albeit a bit too wide for the narrow LW rim shape. I figured it would be nice to have some extra grip this winter.
    Can it really be true that 30’s are more aero and less Crr than 23’s? I’m finding that a hard one to swallow, no matter how wide the rim is.

    • cyclespeed, Thanks for your feedback. I’m a rider too so just trying to figure out what’s real for myself and then share it with you. Generally speaking, wider tires will provide less rolling resistance because of the shorter/wider tire patch than narrower ones. But as I pointed out in my examples above, were talking about a watt or two or so as you go up in tire size. And you’ve got to get tire-rim width combination right otherwise you and more than outweigh the rolling resistance benefit with aero losses if the tire is too wide.

      Wider rims give you more design flexibility than narrower ones to put in the shape or curve to you want in the rim to meet your aero performance objectives. It’s not because the rims are wider that you get aero benefit, it’s because you can put in. You want to get the air coming off your tire to stick to the rim (and coming off the rim to continue on your tire) to maximize the “lift” or aero benefit.

      While we are all describing the “elephant” from a slightly different perspective, Simon has got it right though he may put more emphasis in some areas than I would. For example, a general rule of thumb that Zipp established years ago is to have the mounted, inflated width of the tire be no wider than 95% that of the rim at the brake track.

      As to the ENVE 4.5 AR, they do look to have a lot of all this figured in. GCN is a business with investors and advertisers etc and they are promoting the ENVE a bit here – they also had a contest for one – but I generally find them pretty honest and very entertaining. Steve

      • Thanks for that. That 95% rule It makes complete sense for aero gains. The 25’s on the Lightweights are quite bulbous so without a doubt an aero loss there, but I’m only trying it on the rear so far, so mitigated to some extent.
        But the surface frontal area of a 23 is 0.0154m2, and for a 30mm 0.021m2, i.e. 36% higher, so the Cd of the 30 (taking into account the rim profile) needs to be at least 36% better than the 23 to make up the difference. A tough call.
        And although the weight difference between 23 and 25 is insignificant (my Vittoria CX’s had a 11g difference), the difference between 23 and 30 does start to be felt, especially if the wide rim also adds some weight.
        And at what point does the ‘wider rolls better’ rule break down? 35, 40?

        • cyclespeed. The frontal area of the tire is insignificant when figuring overall aero performance. (the width of your shoulders, your position on the bike, the shape of your helmet, etc. are all much much more imporant.) The drag differences kick in when your rims are at various yaw angles to the wind and the air is coming off your tires and rims. How well and how long the air reattaches to your rims and tires determines how aero the wheels are.

          Likewise, weight differences between tires is also very small considering everything else. Most mortal riders really can’t tell the difference less than 150 grams in a wheelset anyway.

          Steve

          • All frontal area is significant surely? I realize that the body accounts for something like 80% of total drag, but aero handlebars for example are sold for a reason, and are effective at reducing both frontal area, and Cd. Drag force = 0.5 x Area x Cd x Airdensity x velocity squared.
            Yaw angles are typically low, i.e. 0 to 10′ so frontal area is still important, even if I agree that the tire/rim interface is also important.
            Looking at bikes like the Venge Vias or Madone for example, show how every effort has been made to reduce frontal area AND Cd.

          • All true but tire frontal area, aero bars, latex tires, etc, matter only to racers, TT, track riders and other elite athletes at the margins. Just saying the RELATIVE importance of those things is far less to the point of insignificance for most enthusiast level riders. What matters more is detailed in my 2-part series on how to ride faster covering both technique and gear. If you haven’t read it, check it out. Would be great to know how it compares with your experience. Cheers, Steve

          • Thanks Steve. I’m a part time cycle guide, cover about 16000km/year and was 9th vet in this year’s Etape du Tour, and I am interested in those marginal gains, especially as I am light (63kg) and relatively low outright power.
            Your 2 part guide is well written though and no doubt very useful to those looking to learn some tips.
            I just have a hard time looking at 30+ tires on a race bike, but maybe 28 is the new 23….

          • Understood. As you read above, I still can’t see a good reason for putting 25C tires on most of today’s wheelsets, especially if you care about speed.

            Let’s end where you started and steer clear of the marketing hype.

  • Hi Steve. I really enjoy reading your articles. I am 53 and recently got back into cycling this year at the recommendation of my cardiologist. I just purchased entry level Fulcrum Racing 7LG wheels which are 17c inside 23mm outside. I have the stock tires, Kenda Kontender 26c on the rims now. I would like to upgrade the tires to perhaps a Continental tire and would like to know which model and size you would recommend for the basic wheels I have now. I am not looking to break any speed records, just want to be as efficient as I can be while riding.

  • May i know who makes 25mm wide 50mm deep wheels with 622x19c(inner width)… Most of them i know have 17 or 18 inner width (zipp, reynolds, hed)

    • Drashkum, There are some (Bontrager Easton). Look at the chart on this page for starters. Steve

      • Thats was a quick reply.. But unfortunately those are tubulars and i run a clincher :(. I got a pic from a custom carbon wheel maker here which is categorically 25mm(external) wide 50mm deep U shaped rims (internal 17.5mm) with angled break tracks (12mm) and wheel goes as wide as 28mm at widest part. Do u think a 23C tyre would be ok in this for speed?. Im so sold by your writeup that i dont want to deviate from any of your ideas. Do please let me know

  • D, They may sell the Bonti and Easton wheels in tubbies but the ones I reviewed are clinchers.

    A 23c clincher tire on a 17c rim is going to measure 24.5 to 25mm once mounted and inflated. S

    • The Easton/Bontragers are 27/28mm wide ones. Only these are 19Cs. There are no 25mm wide 19Cs in the market to mount a 23C tires. I think Eastons/Bontragers are the only way out

  • Thank you so much for your extremely well written article! It answered several questions that I have searched for answers to, but never found!

  • Got a Reynolds Strike wheelset and put on some Pro 4 SC 25’s thinking they were the “right” width for the 25 wide Strike rims. As you point out, inflated tire widths often don’t match what’s shown on the sidewall. After reading your article I measured the inflated widths of the 25’s mounted on the Strikes and sure enough, they both measured 28. So, I switched to some Pro 4 SC 23’s I had and they measured just under 25 on the Strikes. I was really surprised how much quieter the wheels were when I first took off – the “swooshing” noise I thought was normal for deeper rim carbon wheels is all but gone – so much quieter. I assume the difference is due to the better aero performance with the narrower tires?

    I have the Strikes on a 2014 Cannondale Synapse Hi Mod with Ultegra build. I use the Strikes as all-around wheels and am pleased with their performance in crosswinds – not a problem.

  • Hi Steve, I just bought a set of Zipp 30 Course wheels to move between a few bikes and neither me nor my LBS shop could get a pair of Conti GP4000s mounted (with a tube) – they just wouldn’t go on and would be useless if I ever got a flat during a ride. If so, what 700×28 ROAD tire would you recommend? I’d be open to tubeless too. Thanks!

    • Paul, It’s not about the tire or tire width, it’s about putting tires on wider rims a little differently than you do with narrower rims. Put one side of the tire in the center of the rim channel (not up against the side of the rim) as you put on the other side of the tire. That should do it. Steve

  • So glad I found this article! I’ve been in search for a carbon wheel set but with the different tire sizes and rim width options it just made it difficult to choose! Thanks for the great article!

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