THE BEST WIDER ROAD BIKE TIRE AND WHEEL SIZES
How wide should the tires be on your road wheels? Here are my recommendations for the best bike tire and wheel sizes to improve speed, comfort, and handling.
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 or 28mm wide 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 simplistic, incomplete or, depending on your set-up, a 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 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.
Related: Road Bike Wheels – How To Choose The Best For You
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 look at what the interrelated effects are of using a wider tire or wheel rather than looking at them in isolation as most do. For example, what effect does 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 to cyclists in general or to triathletes, commuters, recreational, or gravel riders who ride 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 bike tire and wheel sizes for road cycling enthusiasts based on your comfort, speed and/or handling priorities.
In a previous post (currently being updated), 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 come with wheels that are designated 17C or are 17mm wide between the tire bead hooks that run along the inside of each rim. These bikes are also generally specified with tires that are 25C or 25mm 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.
If you look at the bikes Bike Radar selected for their bike of the year awards back in 2016, you’ll see that 3 out of the 4 rim brake bikes that were picked as the best in their price ranges were sold with 15C stock wheels while 2 came 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 were equipped with 15C wheels and 8 with 25C tires.
As is the case with most new bikes, none of these wheels or tires were, or today are, high performance or terribly comfortable, no matter their size. Unfortunately, you don’t usually have the choice to switch stock wheels and tires for another set without an extra charge or for most, take delivery of the bike without any wheels and get the price reduced.
Skip forward to the present day and most stock wheels on new disc brake, enthusiast-level road bikes (which far outsell rim brake ones) use 17C or 19C rims and 25C or 28C tires. If you have a model year 2016 to 2018 bike (rim or disc brake) it’s likely in the narrower of those two options. Since then, the newer the bike, the more likely it is a road disc bike and has 19C rims and 28C tires but many still are sold with 17C rims and 25C tires.
You’ll often see these rim widths referred to as 622x17C or just 17C on the wheel spec sheets and as 700x25C or just 25C 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 17C stock wheel rims typically have an outside width of 21-23mm wide across their brake tracks, 19C stock wheel rims typically run 25-27mm outside widths.
The drawing below shows these rim width ranges and also the rim profile that often, though not always, accompany these widths.
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 because it is badly out of date.
Why? The ETRTO chart doesn’t account 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 other use scenarios and product designs that have come about since the standards were developed.
Many of the leading wheelset companies recommend tire widths narrower than the ETRTO ones to maximize aero performance. Most design their rims for 25C tires and don’t recommend you use anything wider than a 28C tire. These rim/tire width combinations run safely.
WHY RIDE WIDER WHEELS AND TIRES
With that as background, what changes when you move to rims wider than 15C or 17C and tires wider than 23C or 25C? 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.
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 70 to 90psi (and tubeless ones 10-20psi 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 it 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.
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 5000.)
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 wheels that come on new bikes sold before 2016 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.
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.
Let me review each of these individually.
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 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 are 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, uninformed 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 directly into the wind (or 0 “yaw”).
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. Testing done by Hambini (here), rejects the conventional approach of testing wheels assuming steady winds coming this narrow range and instead measures a more dynamic and wider range of wind speeds and directions to emulate the real world of bike riding.
Starting 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 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.
I’m not saying that you can’t put a toroid profile on a 15C or 17C wide, 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.
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 28mm tire on my XYZ wheel?” But, I’ve also heard questions like “My budget is x. What wheel would be best with a 28mm 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 has rolled through the enthusiast peloton.
To the first question, I almost invariably answer that if you are riding at 18mph or 29kph and faster and using wheels that are at least 40mm deep, you don’t want anything wider than a 23C tire if you want to maximize speed unless your outside wheel width is at least 28mm. If, however, you don’t ride that fast or have a wheel that deep or you put comfort ahead of speed, go ahead with the 25C tire.
There are no wheels that are 25mm to 27mm wide and at least 40mm deep 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.
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 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 re-attaches. 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.
The toroid rim profile and rim length are 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 and their 28mm or wider outside width rims around 25C tires. Of course, many of the best 23C tires (often labeled 23mm) actually measure between 24mm and 25mm wide when mounted and inflated depending on the tire model and rim size it is mounted on. Likewise, 25C or 25mm labeled tires usually measure 26mm or 27mm wide.
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.
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.
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 magazine – the highly analytical German cycling review publication – actually ran tests using a stunt rider to test and establish tire grip ratings. 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 or a 25C to 28C 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.
Now if you reduce your tire pressure on the wider tire to get more comfort, you’ll get a even 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 sidewall shape as you can see in the drawing on the left.
The problem comes when riders, having read about all the benefits of wider tires, mount a pair that’s too wide for the 17C or 19C wide alloy stock wheels that came with most of our new bikes or the upgrade alloy rim brake 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 bike tire and wheel sizes 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.
Modern rim brake wheelsets for road bikes range up to 19C with a few up to 21C. Most road disc wheelsets are no wider than 21C. None of the companies that make these wheels recommend putting 32C or 35C tires on their wheels. Further, few rim brake road bikes will fit a 28C tire between the rear stays. Likewise, few road disc brake bikes will fit a 35C tire.
The ETRTO standards also 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 changes.
The chart is a guide that needs to be updated or tossed when considering the real world that road cycling enthusiasts live in today. Wheel and tire makers have been holding meetings to update it for years without agreeing on new set of standards while trying to get bike manufacturers to widen the spacing between the chain and seat stays and the front forks.
Meanwhile, most wheelset companies recommend an appropriate tire width for their wheels.
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 on bikes made before 2016. You know how it rides. This is still a perfectly good width combination in my view. What follows are your options.
A 25C tire on a 15C wheel – somewhat improved comfort over a 23C tire but worsened speed and handling for reasons described above. 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, is >35-40mm, and you are riding at 18mph/29kph or faster.
A 25C tire on 19C or 21C wheel – better 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) especially on deeper (>35-40mm) and preferably rounded profile wheels. But, most alloy wheels aren’t going to be that deep or have a rounded rim profiles where the spokes join the rim.
A 23C tire on a 19C or narrower wheel – best speed. If you’ve chosen this set-up, crits, road races or TTs and triathlons are probably your passion, deeper aero wheels are probably your preferred hoops and comfort is 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 for a wider tire.
A 28C tire on a 19C or 21C wheel – best comfort but at the expense of speed if you put them on a deeper aero wheelset. There’s also a likelihood that the tire – which will likely measure 30mm or wider – won’t fit between the rear stays of your rim brake bike and earlier model disc brake bike.
A 28C tire on a 17C or 15C wheel – handling could be seriously compromised with this combination. You are also likely to get an increased number of pinch flats. Also, as with the combination above, it’s likely the tire won’t fit between the rear bike stays or inside your rim brake calipers.
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Thanks and enjoy your rides safely! Cheers, Steve
First published on April 3, 2016 but updated regularly since as new wheelsets and tires have been introduced. The date of my most recent major update is shown at the top of the post.