In my post Why and When to Buy a Road Disc Bike, I described the braking, speed and versatility benefits that convinced me to recommend that road cycling enthusiasts get or build a bike with disc brake components and wheels when they buy their next bike.  I also laid out when would be the right time to make that purchase over the next few years depending on whether you are an enthusiast primarily focused on racing and competing or endurance riding and events or general fitness.

In this piece, updated in early 2016 to account for newly introduced models, I’ll give you my design, product and performance evaluations and my purchase recommendations for disc brake components.  In two more posts, I’ve provided similar types of reviews of road disc bikes and wheelsets.


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When talking about disc brakes, there are several components to consider.  There are the brake calipers, pads and rotors that the calipers squeeze to create the friction for braking.  There are also the integrated shift and brake levers that control the braking action, and the tubes and hydraulic fluid that run between the levers and brakes.  All of these together make up a disc ‘brakeset’.

I know, brakeset is industry jargon like ‘wheelset’ and ‘groupset’ but it’s a helpful shorthand to cover the different items that go into braking without listing each of them individually over and over again.


The arrival of road disc bikes for the enthusiast level rider comes in large part due to the introduction between 2012 and 2014 of integrated electronic or mechanical shifting and road disc brake levers from Formula, SRAM and Shimano that use hydraulic fluid rather than cables to control the brakes.  In these systems, you move your brake lever and the push from hydraulic fluid pressure, rather than the pull of a cable, closes the brake caliper over a rotor mounted to your wheel.  I’ll call this a ‘hydraulic-disc’ brakeset.

Brakes - rear set up - Bike Radar

A rotor and rear disc brake caliper bolted to the rear stays and fed by a hydraulic line coming out of the chain stay

There are two alternatives to hydraulic-disc brakesets.  A ‘cable-disc’ brakeset has brake levers that connect to and actuate disc brakes using traditional brake cables.  You’ll see a fair number of cable-disc brakesets on lower cost bikes.  With a ‘hydraulic-rim’ brakeset, your brake levers control hydraulic fluid that runs to calipers closing on your wheel rims rather than on rotors.

As an aside, note that some use the term ‘mechanical-disc’ brakeset for what I call cable-disc brakesets .  They are the same thing.  I find the term mechanical-disc confusing as there are also mechanical (and electronic) shifters with integrated brake levers.  Some of the mechanical shift/brake levers connect and actuate the brakes using hydraulic lines and some use cables.

Both the cable-disc and hydraulic-rim these alternatives provide less performance benefit than you get from a hydraulic-disc brakeset.  The cable-disc gives you less power and control and the hydraulic-rim has similar wet weather and downhill braking performance as regular rim brakes.  I recommend against both of them if you are planning to buy a new road disc bike.

Before hydraulic brake levers came along, you could only get cable-disc brakesets supplied by companies including Shimano, Avid (owned by SRAM), TRP and Hayes for road or cyclocross bikes.  You will see 2016 model year cable actuated disc brakes, mostly on sub $2500/£1500/€2250, aluminum road and off-road bikes with tier 3 and lower level  groupsets like the Shimano 105, Sora and Tiagra models.

Campagnolo has not introduced a disc brake system or announced their plans beyond their CEO commenting they would not launch anything until 2016 to be in sync with the pro race circuit adoption path rather than the enthusiast consumer road cyclist one.  As of early 2016, there is still no official news a Campy’s hydraulic disc brake program or offering.  A few of the companies or bike builders will special order/configure a Campy top end mechanical or EPS groupset with a cable-disc caliper and rotor from TRP, but I don’t really see the point of that unless you are unwilling to ride anything but Campy and want road disc.

I haven’t found either hydraulic-rim or cable-disc brakesets on new 2016 model year standard equipment carbon road bikes, the favored frame material and price point at and above which you’ll find most road cycling enthusiasts’ bikes.  Since my focus is on the road cycling enthusiast riders, I’ve only evaluated and will only refer to hydraulic-disc brakesets and road disc bikes using this kind of brakeset in the remainder of this post.

Hydraulic levers offer the benefit of better control and feel, or what’s called ‘modulation’.  They use the superior power and friction-free, progressive flow of the hydraulic fluid to reduce the amount of effort required from your hands to brake so you get more ‘touch’ or ‘feel’ in your braking.  With the touch of a finger or two on your hydraulic brake levers, you can consistently brake hard and late going into corners with confidence, readily use your brakes down long descents without fear of your rims overheating (since disc brakes don’t touch the rims), and you won’t feel your brakes get spongy or fade if you are braking for a long time.  And you can do this in dry or wet conditions with equivalent brake response.

While integrated shifters and brake levers are standard on rim brake bikes, designing them with space for the hydraulic brake cylinder and reservoir was quite a neat bit of engineering.  SRAM didn’t get it quite right on their first go in 2013. They recalled their hydraulic shifters later that year and re-designed and replaced them in the second half of 2014.  Shimano have had better success, launching integrated shift and brake levers without incident for their Di2 electronic groupsets in 2013 and for their mechanical shifting sets in 2014, each for the next model year.

Cutaway of SRAM's integrated mechanical shifter and hydraulic brake lever. Photo from SRAM

Cutaway of SRAM’s integrated mechanical shifter and hydraulic brake lever

For their first road brake calipers and rotors, Shimano essentially rebadged products with technology they’ve used successfully for a number of years on their mountain bikes.  They’ve since developed ‘flat-mount’ calipers for road bikes that mount on the rear chainstay for a clean look and more aero fit.  SRAM developed road bike specific disc calipers and rotors based on the experience if not the same designs used in their Avid mountain bike components business.

The design challenge for road bike calipers, pads and rotors is to find ways to cool the heat created during braking.  Shimano, for example, use 140mm rotors made of aluminum bonded between surface layers of stainless steel to draw the heat away from the braking surface.  They have also designed-in cooling fins along the inside edge of the rotor’s braking surface and atop its calipers for the heat to exit as shown in this photo.

Brakes - Cannondale Synapse Carbon Ultegra Disc - road cc

Photo from

SRAM favors the use of larger area 160mm, all steel rotors rather than fins to disperse the heat.

Brakes - SRAM-Rival-22-Hydro-group-reviewroad-bike-disc-brake-Rumor

Photo from Bike Rumor

The respected German cycling magazine Tour Int. did rotor testing and established some conservative guidelines I’ve listed here for Shimano rotors based on rider and bike weight.

140 mm Shimano Ice Tech rotors:

  • Flat terrain
  • Cyclo-cross with little elevation gain
  • Hilly terrain with gradients less than 10% and total weight (bike and rider) up to 85kg/187lbs

160 mm Shimano Ice Tech rotors:

  • Flat to hilly terrain with total weight (bike and rider) up to 100kg/220lbs
  • Alpine terrain with long descents of less than 15% and a total weight up to 85kg/187lbs

160 mm all steel rotors:

  • Flat to hilly terrain with total weight (bike and rider) up to 120kg/265lbs
  • Long and steep descents over 15% and a total weight up to 100kg/220lbs

The leading bike brands have basically ignored these guidelines, instead putting their trust in Shimano’s testing and conclusion that 140mm rotors work for all but the heaviest riders.  In most cases, frame and wheel set-ups and clearances allow you to make your own rotor size choice.

Since most of your braking should be done on your front wheel, another option for riders is to go with a 160mm front rotor with a 140mm rear rotor.  I’ve seen this set up on several 2016 model year disc brake bikes that have Shimano disc brakesets and this is a good option for heavier riders.

Why not just go conservative with 160mm rotors and be done with it?  For some, the weight or looks of the larger rotor is a turn-off.  Others feel that specifying more than is needed gives you more braking power than you really want.  (My lawyer friends have told me not to recommend one size or the other.)  Shimano and SRAM each make both rotor sizes so you can also make your own choice.

A lot of work is also going into reducing the weight added by going to disc brakes.  Shimano’s RS785 electronic shifting brakeset and RS685 mechanical shifting brakeset each weigh about 350 grams (353g and 358g respectively, to be exact) over the rim braking Ultegra 6870 Di2 and 6800 mechanical groupset components they replace (hydraulic shifter/brake levers, disc calipers and rotors for electronic or mechanical shifter/brake levers and rim calipers).

The rest of the roughly 450g or so of average current weight penalty for going disc comes from the frame and forks (typically about 50-75g) and slightly wider and beefier wheelset hub and extra front wheel spokes (also about 50-100g).

I addressed the weight concern in a post about why and when to get a road disc bike.  In summary, unless you are a very fit racer, a pound or two of non-rotating mass or weight will not make a discernible difference to the performance of your bike or speed of your ride.  If you think it does, take only one water bottle on your next ride and let me know if you can tell the difference.  Or if you only take one normally, take an extra one with you next time out and see if you notice any change in speed or handling or anything else.


A full 22oz or 650ml water bottle weighs 773 grams, far more than the average 450 grams added by going to a road disc bike from a similar model with rim brakes

Beyond weight, there are three other concerns some mention when considering getting a bike with disc brakes: 1) they are noisy, 2) they are more complex and need more maintenance than rim brakes and, 3) they are less aerodynamic.  I don’t think any of these are issues but let me take them one at a time.

Noise – Disc brakes should only be noisy during a brief period when you ‘bed-in’ or smooth out the surface of the rotors and pads.  Bedding in can be done simply by pedaling up to your normal speed and then using the brakes to gently and gradually slow your bike until you are riding just a couple of miles per hour.  Repeat the process about 20 times and your brakes will be ready to ride full on without any noise.  Don’t brake hard or come to a complete stop.  Bedding in is a noisy process and not my idea of a good time, but once done your brakes will be quiet.  Perhaps you can do it at an empty school parking lot on a weekend morning or mid-week evening.

This is essentially what you need to know to properly break in (pun intended) and silence your disc brakes but if you want to read more about this and the choice between organic and metallic pads, check out this good article from Art’s Cyclery.

Maintenance – When it really comes down to it, disc brakes should be easier to maintain than rim brakes.  If your rim brake ‘maintenance’ amounts to changing out a front pad every now and then, what I just wrote is wrong but then again, you probably aren’t real safe on your bike.

If you really do maintain your rim brakes, you should be doing the following:

  • keep the brake cables clean to minimize the extra friction from road dirt that collects on them.
  • check the cable ends to make sure they aren’t fraying and replace them when they are or when the cables are corroding,
  • keep the calipers centered and the pads braking on the middle of the rims especially after you take off and put on a wheel,
  • wind the barrel adjusters or reset the cable lengths periodically to keep the caliper openings and brake lever pull or stroke distance and tension consistent as the pads wear,
  • keep the calipers, adjusters and springs clean and lubricated,
  • toe in the brake pads if necessary to reduce or eliminate noise,
  • and yes, replace the brake pads when needed

Here’s a good video on adjusting rim brakes and another on replacing your brake cables that goes into more depth about rim brake maintenance.

With hydraulic-disc brakes, the biggest and really only maintenance job needed is to fill the brake lines with specified mineral (Shimano) or DOT (SRAM) oil and bleed them of any air.  If you have a mountain bike, you may be familiar with this well established process.  If not, here’s a thorough video that lays it out.

Basically you fill the system from the rear caliper and bleed it from one of the brake levers through fittings built into those disc brake components.  It’s rather simple to do and there’s a kit which has all you need but you should be disciplined about it to do it right.

While the videos show that both replacing cables and bleeding your brakes are quite doable, many of us enthusiasts will take our bikes to the shop to take care of these jobs.

Once you have filled and bled your brakes, typically as part of a winter or spring tune-up, and you’ve properly bedded in any new pads you’ve put on the bike, there’s minimal if any adjusting you’ll have to do to the brakes during the season. Thanks to the pressure of the fluid, hydraulic brakes self-adjust their caliper center position and opening gap as well as the brake lever stroke so there’s no need to regularly check and tune those.

You’ll want to keep your disc pads clean of dirt and oil and replace them when necessary, the later being just as easy if not easier than with rim brake pads.  Here’s the link to a good BikeRadar article with some tips on road disc brakes if you are home wrench and some tips from Art’s if you want to see how the pros service disc brakes.


As with anything else on your bike, if you crash or mishandle it in transport, you may need some service.  Most common in these situations is a brake rotor that gets a little bent.  You also may want to run some 120 grit sandpaper over your pads or rotors to remove some glaze to extend the pad life a little.


While Shimano has their Dura Ace, Ultegra, 105 and other groupsets for rim brake bikes with complete sets of disc brake components including shifters, brakes, chainsets, derailleurs, etc. at each level, they haven’t given family names to their disc brake groupsets yet.  Still, it is possible to make some sense out of their RS nomenclature and align them with groupset levels.  Here’s my best take at what they offer with explanation to follow.

Shimano Disc Brake Components 2016

Shimano makes the RS785 hydraulic-disc brakeset designed to work with their Dura Ace 9070 Di2 and Ultegra 6870 Di2 electronic groupsets.  This usually come as a kit in combination with the ST-R785 shifter/brake levers with the top or Dura Ace level BR-RS785 disc brakes.  You may also see the Ultegra level BR-RS685 brakes grouped on new bikes equipped with the ST-RS685 brakes on bikes which otherwise have Ultegra derailleurs and other Ultegra family of disc brake components.

For their mechanical groupsets, they make the ST-RS685 shifters to go either with with their Dura-Ace 9000 or Ultegra 6800 mechanical derailleurs.  These come in kits and on new bikes typically with BR-RS685 brakes but I’ve seen BR-RS785 brakes with them as well on some of the 2016 bikes.

For 2016, Shimano introduced “flat mount” brakes which mount flush on the front fork and rear chainstay rather than through raised bumps or ‘posts’ on the chain or seat stay as shown in the photos above.  Posts are also used on the front forks to mount the brakes.  The BR-RS785 and BR-RS685 are “post mount.”  The post mount brakes are carryovers from the mountain brake line.  The flat mount brakes are designed for road bikes and tuck the brakes in to provide a cleaner look and, in theory, a more aero set-up.  I haven’t seen any testing to confirm the aero claims.

Shimano’s flat mount design makes for a cleaner installation that’s easy to access

The biggest benefit of flat mount brakes, frankly, is the space it saves on the frame and the ease of which you can access the calipers.  So chapeau to the Shimano for coming up with this standard and making the life of shop and home wrenches a bit easier.

Your frame must be designed for flat mount brakes to use them and only the newest frames are.  You can mount post mount calipers on flat mount frames with an adapter but you can’t do the reverse.

At the same time as Shimano introduced the flat mount brakes, they extended the hydraulic-disc line to the third tier 105 groupset.  This line only has a mechanical shifting option and they use the ST-RS505 shifter/brake lever at this level and usually pair it with the BR-RS505 brakes.  Shimano also introduced the BR-RS805 flat mount brakes, an Ultegra level brake that is showing up on 2016 bikes that designed for flat mounts brakes that also have Dura Ace or Ultegra electronic or mechanical groupsets.

Hope this explanation and the chart makes all of this a bit easier to decode.  If you are building up your own frame, I have links at the end of this post to where you can get all of these components at the best prices I’ve been able to find from stores with excellent customer satisfaction ratings.

For all of these, the the Shimano Ice Tech Freeza rotors are sold separately.

SRAM is a lot easier to explain.  They sell Red 22, Force 22 and Rival 22 HydroR hydraulic-disc brakesets.  These are slightly different kits for each groupset level.  As with the Shimano groupset components at different levels, weight and materials are the primary differences between the SRAM components, consistent with how they design their other groupset components.  As with Shimano, the rotors are sold separately.

SRAM is adopting the flat mount standard.  A nice photo here shows the post mount (top row) and flat mount calipers here.

SRAM has yet to introduce an electronic shifting groupset for its hydraulic brakes.  With their eTap electronic groupset just coming out for their Red 22 rim brake groupset in 2016, I wouldn’t expect an electronic shifting, hydraulic braking groupset from SRAM any sooner than 2017 if then.  I base this guesstimate on the priority and engineering resources SRAM is likely to have spent since 2014 on the electronic groupset, the time required for development and testing of an electronic HydroR brakeset, and the very deliberate approach SRAM will likely take to a new hydraulic brake lever after the problems that forced it to recall its first one.

While Campagnolo has its EPS electronic shifting groupsets, it has not developed a hydraulic brake system as yet.  You can configure a few road disc bikes with a Campagnolo groupset and cable actuated disc brakes supplied by TRP, though I think that is sub-optimal for the reasons I described earlier about cable-disc brakesets.

As you can see, each of the companies is taking a very different approach.  Shimano entered with an electronic shifting hydraulic-disc brakeset and moved within a year to add a mechanical shifting hydraulic-disc brakeset and then a third tier mechanical shift/brake levers and flat mount calipers for all tiers.  None of these are badged as Dura Ace, Ultegra or 105 groupset series.

I’d expect we’ll see series-specific brakesets in the next year or two, differentiated only by their materials and weight rather than their function and performance.  Worth waiting for?  I don’t think so.  The difference between SRAM’s top-tier Red 22 and third tier Rival 22 hydraulic-disc brakesets is only 44 grams.

Meanwhile, Shimano have moved quickly and successfully to be the hydraulic-disc brakeset specified on most new road disc bikes.

SRAM, also have the new road disc bike market in their sites with their ‘hydraulic-disc’ option integrated into their Red, Force and Rival levels.  They’ve never been able to capture more than a small portion of the OEM groupset market against Shimano though they are the only true competition to Shimano as Campagnolo appear to have all but abandoned this channel to focus on selling their groupset components in the after-the-bike-sale or ‘after market’.

With their ‘hydraulic-rim’ option, SRAM also appear to be targeting current road rim brake bike owners who want to switch to hydraulic brakes, but do it on their current frames, thereby sparing the cost of buying a new bike and wheelset.  That’s a smart strategy for those of us who aren’t ready just yet – either because our current bikes and wheelsets are in good shape or our bike gear budget isn’t – to add a new frame, groupset and wheelset but still want some of the benefits of going to road discs.

The Italian brake and components company Formula were the first to design hydraulic brake levers integrated with Di2 shifters.  They didn’t work well when initially introduced and I haven’t seen any recent reports or reviews on them.  Formula brakesets aren’t equipped on any new enthusiast level bikes this season offered by the 18 reasonably well-distributed bike brands I’ve identified.

Campagnolo, with less groupset sales and likely a smaller engineering team than either Shimano or SRAM, have probably not been able to marshal their resources to develop a hydraulic solution.  They spent a good part of 2014 designing a complete new mechanical groupset line up for model year 2015.  They were rumors that they were working with Formula to come up with a disc brake solution but there has been nothing out of Campy on this.

Even if they had the resources, Campagnolo’s strategy to command high prices on premium products has been based on road cycling enthusiasts following the lead of the elite professional riders.  As mentioned earlier, the pros are way behind on road disc bikes, likely not to begin thoroughly testing them in races until 2016 and perhaps then, even sparingly.


Fortunately, for those who want to go with electronic shifting on a disc bike, the Shimano RS785 hydraulic-disc brakeset coupled with the Dura-Ace or Ultegra Di2 system was well received and is available on a good range of 2015 model year bikes.  The integrated electronic shifter and hydraulic brake lever (ST-R785) has the same ergonomics as the standard Di2 integrated shift lever; it feels nearly identical when you put your hands in the hoods.  Some have made mention of the slightly taller hydraulic Di2 shifter hood body but this is an aesthetic difference only.

The same goes for the mechanical shifting, hydraulic braking Shimano lever (ST-RS685) and its cable braking sibling. The width and ergonomics are the same but somehow they’ve managed to design space for the hydraulic fittings into the body along with the mechanical shifters.  The hydraulic braking lever extends a little longer than the standard cable brake one, perhaps helping to making room for the hydraulics in the hood body without having to make it any taller.

Here are some comparative photos.

Brakes - R785 vs regular Di2 shifter - Bike Radar

Ultegra Di2 shift/brake lever (left) vs. R785 Di2 shift/hydraulic brake lever. Photo – Bike Radar

Brakes - SRAM mechanical vs hydro levers - SRAM

SRAM mechanical vs. HydroR levers. Photo -SRAM

Rolling back the shifter cover, you can easily use a screwdriver to adjust how far out your levers sit from the handlebar (up to 10mm of ‘reach’) to accommodate the size of your hand and how soon the braking kicks in once you start pulling on the levers (the ‘stroke’). You do this on initial set-up and you are done; you don’t need to adjust as your brake pads wear.

When it introduced its mechanical shifting hydraulic disc brake lever, Shimano also updated its brake caliper slightly.  The new BR-RS785 and BR-RS685 calipers (vs. the old BR-R785 without the S) makes the hose routing a little easier for road bikes.  The hose now comes into the top or inside of the caliper; before it came into the side or outside of the caliper.  This makes installation and filling a touch easier but doesn’t change the performance.

On the road, the Shimano brakesets deliver on the promise of disc brakes.  Both the Di2 and mechanical shifting are unaffected by the presence of the hydraulics and they shift and brake equally well whether your hands are in the hoods or drops.  You can deliver braking power with less effort and more feedback.

Even going down a steep hill, you brake easily with a finger or two on the hydraulic brake lever to get just the right amount of deceleration you want rather than wrapping your hand, from fingers to palm, around the mechanical brake lever and hoods or drops, forcefully grabbing the brake while hoping you don’t lock up or skid out.

You get the kind of feel, more finely controlled braking and consistency of braking regardless of the road surface with hydraulic disc brakes that you just can’t get with mechanical rim brakes.  Rather than overwhelming your brakes and bike, the additional power available in Shimano’s hydraulic-disc brakesets are tuned to allow you to use less of your own, getting the same amount of force to the brakes, but in a much more finely controlled way.

After a short time riding with hydraulic-disc brakes, the naysayers and believers alike say something like “I never imagined how good it could feel to brake.”

The redesigned SRAM HydroR integrated hydraulic braking groupsets successfully completed their first competitive campaign on the US cyclocross circuit during the 2014/2015 winter season.  With apologies to Richard III, this “made glorious” the prior “winter of our discontent” surrounding the recall of the company’s original integrated shifter and brake lever design.

The response and transparency which marked the recall of the initial SRAM hydraulic system and the design changes made both to address the hydraulic cylinder problems and improve the ergonomics were significant, detailed and a great example of everything you would want as a consumer. (See here for more)

In terms of what you can see and feel now, the functional improvements (beyond the fitting changes) are a reduction in the stroke or distance you need to move the brake lever to get it to engage (eliminating “dead travel”), a smaller shifter panel providing more room for your fingers when in the drops and while wearing gloves, and a new spring in the disc caliper to get the pads opening more quickly.

Aesthetically, the SRAM HydroR hoods are tall, markedly taller than either of the cable actuated SRAM hoods or the Shimano hydraulic ones.  The 160mm rotor also looks big compared to the 140mm ones.  I’m typically less focused on the look of a bike than on its performance, but for those of you who rate looks high on your list, you’ll notice the SRAM hoods and rotors more than you will the Shimano ones.

I’ve previously recommended going with an electronic groupset over a mechanical one if you can afford it and specifically with the Ultegra 6870 Di2 over the Dura-Ace Di2 or EPS gruppos from Campagnolo.  As I said in my groupset review, the recommended Ultegra Di2 “performs better than mechanical ones, is more enjoyable to ride, and requires less service.   It will enable you to go faster than you would with the best mechanical groupset.”  I describe why this is the case in more detail later in the same review.

As for mechanical groupsets, I recommended the Ultegra 6800 over others from Shimano, Campagnolo and SRAM as the best value, considering both the performance and cost criteria that I detail in the review.

For much the same reasons, and adding the fact that the SRAM brakesets are twice the price of the Shimano ones now for no good reason that I can determine, I’d recommend the Shimano RS785 and RS685 brakesets with Ultegra 6870 Di2 and Ultegra 6800 groupsets and the flat mount BR-RS805 brakeset if your new road disc bike is set up for it.  I wouldn’t change my choice of bike or frame just to get a post mount one if you prefer everything else about one that doesn’t have that design feature.  I would generally stay clear of bikes with the 105 hydraulic groupset (RS505), not because of the of the shifter/brake levers and calipers per se, but because the other components in the 105 set and on the bike it normally comes on at that level isn’t on par with those of the Ultegra or Dura Ace component equipped bikes.

You can also use the RS785 brakesets with the Dura-Ace 9070 Di2 and the RS685 with the Dura-Ace 9000 groupsets.  I don’t think, however, that the road cycling enthusiast gets any benefit spending the extra money for the indiscernible weight savings going to a Dura-Ace or SRAM hydraulic-disc groupset.

And while you can go hydraulic and save a boatload of money by putting a SRAM hydraulic-rim brakeset on your current road bike instead of buying a new disc frame and disc wheels, I don’t think the incremental modulation benefits are worth the cost of buying this set-up.  You’ll still have limitations on wet roads and in the mountains with your hydraulic-rim braking system on carbon wheels.

All of that said, I know that some people prefer the shifting mechanisms of SRAM or Campy or Shimano over the other two for perfectly good personal reasons.  While I think they are all sound and easy to adapt coming from one to the other, I won’t deny that personal preferences and aesthetics or weight may be more important to some than performance and cost.

Here are the page links for these components at the stores I’ve found have them at the best prices, have them in stock and have top shelf customer satisfaction records as of August 13, 2017:

Shimano Ultegra 6870 Di2 Disc Brake Groupset
Evans CyclesMerlin Cycles

Shimano Ultegra 6800 Disc Brake Groupset

Shimano 105 5800 Disc Brake Groupset

Shimano ST-R785 shifter/brake lever STI and caliper brake set for electronic Di2 shifting groupsets sold with BR-RS785 post mount or BR-RS805 flat mount brakes. 
Competitive Cyclist ITK10 (post-mount), Wiggle (post), Chain Reaction Cycles (post), Merlin (flat)

Shimano ST-RS685 shifter/brake lever STI and caliper brake set for mechanical shifting groupsets sold with BR-RS785 or BR-RS685 post mount or BR-RS805 flat mount brakes. 
Ribble (flat)

Shimano ST-RS505 shifter/brake lever STI and caliper brake set for mechanical shifting groupsets sold with BR-RS785 and BR-RS685 post mount or BR-RS505 flat mount brakes.

Tredz ITK10 (post)

SRAM hydraulic groupsets and components available at recommended stores below

Force 1:  Competitive Cyclist ITK10, Wiggle, Chain Reaction Cycles, JensonUSA

Rival 1Competitive Cyclist ITK10, Wiggle, Chain Reaction Cycles, JensonUSA

SRAM Red HydroR shifter/brake lever and disc brake set 
Competitive Cyclist ITK10, UK/EU Wiggle

SRAM Force HydroR shifter/brake lever STI and caliper brake set 
Competitive Cyclist ITK10, JensonUSA, UK/EU WiggleChain Reaction Cycles

SRAM Rival HydroR shifter/brake lever STI and caliper brake set 
Competitive Cyclist ITK10, JensonUSA, UK/EU WiggleChain Reaction Cycles

Note that Shimano sells kits that include both left and right shifters and front and back calipers in the same package while SRAM sells them as a one shifter-caliper combination (e.g. left-rear or right-front).  This means you have to buy two SRAM kits to fully equip your bike with shifters and brakes.

You may also see some stores selling entire SRAM groupsets with complete hydraulic brakes included as part of them.  I haven’t included these above so as not to add further confusion but I can provide you links to stores offering this if you leave me a comment below.

Got it?  Good.  I admit it’s not simple to sort through.

For more on this topic, here are links to why and when to buy a road disc bike, some of the best 2016 endurance road bikes with disc brakes and road disc wheelsets.

And please, let’s stay connected!  With the follow buttons in the right-hand column on this page, you can sign up to get an email when new posts come out, get posts sent to your RSS reader or follow In The Know Cycling updates on Twitter and Facebook.




  • Great article, sums up my own experience. I have two Giant Defy Advanced Pro 2015 bikes, one the Pro 0 with Di2 and the 140mm disc hydraulic brakes and the other a Pro 2 with 22 speed 105 and cable 160mm discs.
    The difference in braking feel and stopping power is night and day between the two, with the hydraulic set-up vastly out performing the cable.

  • Neil, Thanks for the feedback and for sharing your own experience. Steve

    • Hi Steve, really struggling to figure out what disc is on my Shimano R785, Hydraulic disc, which has 6-bolt 140mm rotors. Can’t find a part number anywhere or how to get another set for planned new wheels. Any ideas??

  • Neil, hard to know without looking at it. To my knowledge (which isn’t vast when it comes to rotors), the 140mm rotors are centerlock but if you have a 6 bolt it’s likely a 160mm. You can find either of these rotors from the better online stores. I’m not aware of 6-bolt 140s from Shimano and I’m pretty sure they didn’t put a 160 with either of their hydraulic disc sets. They are pretty firmly in the 140 center lock camp. Steve

  • I want to put the BR-RS785 on my bike, but I have 160mm 6 bolt rotors. Does that mean I will just need an adaptor/spacer between the frame/fork and the caliper?

    • Yes. That’s it.

      From the good people at Competitive Cyclist:
      “You need to know three things — what kind of mount your Shimano disc caliper is, International Standard (ISO) or post mount. If it goes on the front, you need to know what your fork is: ISO, post-mount, or a few special cases (Marzocchi 20mm axle, Boxxer-type). And, you need to know the rotor size that you’re trying to fit — in this case, it’s 160mm.

      If you’re trying to diagnose what you already have and/or what you need, here’s how to do it. The Shimano adapters all have a model number that starts with SM. The Mount Adapter acronym is MA. Front brake is F. Rear brake is R. Rotor Size is 160, 180, or 203. Caliper Mount Type will be S for ISO/International A, and P will represent Post. And the last letter will be for the frame or fork mount type: S for ISO/A, P for Post, B for Boxxer, Z for Marzocchi 20mm Axle as well as QR20Plus and DH ISO. Thus an adapter that reads SM-MA-F-203S/P is Shimano Small Parts Mount Adapter Front 203mm Rotor with ISO caliper on a Post type fork.”

  • “If you really do maintain your rim brakes, you should be doing the following:

    keep the brake cables clean to minimize the extra friction from road dirt that collects on them, especially along the underside of the down tube (if you have external cables) and under the bottom bracket (all bikes).”

    The only cables that run under the down tube are shift cables. The front brake cable only has to reach the front caliper, and the rear cable runs along the top tube. The only exception would be if you have a rear brake caliper mounted below the chainstays (e.g. – a newer Trek Madone), but if your bike has a brake caliper mounted there, you need a new bike anyway because that’s a dumb place to mount a brake caliper.

  • Also worth consideration is the benefits of hydraulic brakes for what I have called health reasons in the section comments for :-

    Copy and paste to see my comments

    Invaluable for those with arthritis which I have started to suffer with

  • Hi, a really nice article.

    Although RS685 is highly recommended, I still like to wait until Oct to see the new RS505.
    Yeah, current RS685 is still a little more expensive than my expectation, so I’ll wait.

    BTW, when RS505 is out, I’ll upgrade my commuter Fuji sportif 1.1 from cable BB7 road to RS505.
    But what worried my a lot is the fact that, the fork of Fuji sportif 1.1 is with post-mount and 160mm rotor.
    Should I just use the shimano caliper with 160mm rotor?


    • Adam, There’s always something new coming and the trade-off between buying what’s proven now and what’s next and exciting is the gear buyer’s dilemna. In your case, make sure the RS505 flat mount calipers fittings will work with your bike without having to drill anything new. Shimano is saying many front forks will need an adapter. I think these are really intended for new OEM bikes set up for this new flat mount standard but you can certainly use them with an adapter. You can also use the 160mm rotor on any of the Shimano discs. Steve

      • At last, I followed your advice and switched to RS685 STI with RS785 caliper, along with a small wheelset upgrade from the stock wheelset from Sportif 1.1 to DT swiss R24 db.

        Overall I’m pretty happy with the change, and as you implied, my frame is not flat-mount ready, so RS785 caliper is the best choice for my frame.

        Overall, the upgrade is quite good, but it seems the RS685 front derailleur STI needs more force to operate compared to my old 5800 STI.
        And there is no free strike adjustment, unlike the hex bolt from 5800 to adjust brake free strike.

        Another problem is not about the disk brake or wheelset, but it’s somewhat hard to find Shimano dealer who is willing to order that road disk component.

        In my region, MTB is more popular than road, even most of them only ride MTB on tarmac.
        And among guys riding road bike, they are quite stubborn, even UCI accepted road disk, they think that’s just nothing related to normal road rider, and consider a road bike with disc brake a joke.

        So I ordered RS685 with caliper oversea, and that’s almost the RRP from Shimano. 🙁

  • Carlos Galvis Galvis

    Great article. I was planning to spend some money by buying a new bike. I’m a big fan of campagnolo, so I decided to wait what is new for disc brakes system. Thanks again for your article.

  • Excellent piece. Very informative and fun to read. I would suggest reviewing the latest on SRAM eTap, however. I don’t think SRAM has been designed out of their electronic offering and the bike radar article cited above has since been outdated with this one:

    Again, thanks for a great write up.

    • David, Thanks for your kind feedback and suggestion about the eTap. From what I understand, eTap won’t be available for a while (spring) and will only be for rim brake bikes. It’s also been introduced only for the top end Red gruppo, the most expensive in SRAMs line that competes against the Shimano’s top tier Dura Ace di2. While I expect eTap will come to the Force gruppo (competitive with the Ultegra line) and SRAM’s disc gruppos, that is probably a bit further away (Fall 2016 introduction for model year 2017 available that spring). While SRAM’s eTap shifting logic is different than Shimanos and its easier to install, its prace tag puts is above what I’d recommend for most enthusiasts. I likewise don’t recommend the DA di2 because the Ultegra di2 does all that you need for an insignificant amount of added weight and the Udi2 quite a bit less expensive than the DAdi2. The SRAM’s current mechanical disc brake groupsets are also nearly 2x the price of the Shimano ones. SRAM is innovative and a welcome competitor that has pushed Shimano to do design and introduce some things they might not otherwise but I haven’t to this point seen the value of their disc brake or eTap innovations justify the price of their components. Steve

  • Hi and thanks again for the article. I am building a Litespeed T5G with Rs785 calipers and 160mm Ice Tec Freeza rotors. The rear fits fine but the front caliper does not clear the rotor without an adaptor. The forks are Litespeed branded and are said to be flat mount ready. I am struggling to find the correct adaptor on the net and wondered if you could advise. Thanks David

  • I use both disc and rim brake road bikes. My background is mtb and I would never go back to rim brakes on an mtb. I have never really noticed the difference between rotor size in the feel of braking on an mtb, they just work as long as you service them regularly. I have a Cannondale Carbon synapse ultegra disc, it is fitted with shimano ice 140 hydraulic discs. I don’t drag my brakes like most roadies, as I like to brake late and hard, probably a bad mtb habit. Disc brakes suit my riding style. My main issue in the transition to discs on a ride bike has been the feel of the front brake through the fork and headset. The whole front end of the bike feels totally different under braking and takes a lot of practice to use effectively. I think this is what is putting the pros off the transition.
    I don’t think rota size is an issue at all, unless maybe if you weigh more than 80kg, most pros are well below this, and rim brakes are also an issue if you are heavy.
    The main issues worth talking about are wheel and tyre choice, not rota size.
    Advice: keep your weight down, get your wheel and tyre choice right. Disc size maybe a marginal gain after these improvements.

  • Is it ok to store a Shimano hydraulic disc brake equipped bike hanging by its back wheel? Can air get in the system or will oil leak out?

  • Hi Steve, great article! My Genesis Equilibrium 931 frame has flat mount on the rear but the fork is post mount. Easiest solution is to get RS785 post mount callipers and use an adaptor on the rear. But given the nice clean look of the flat mount on the rear, do you think it’s possible to use a RS805 on the rear with a RS785 on the front fork? Thanks.

    • Jan, I’m sure that would work but I don’t know if you can buy just a front post mount and back flat mount. You might want click through the links to the stores I provided to see if they sell them individually. Steve

      • Thanks Steve. That’s good advice.
        The long story is that I’ve already purchased the Ultegra disc group set with flat mount callipers as I was convinced that’s what I needed. I’m now stuck with one calliper that doesn’t fit the fork. So my choice is between returning both callipers for an exchange to post mount (if Merlin will do that) and using an adaptor on the rear, or buying a single post mount RS785 calliper which is available at Evans and other places. They retail at 60 but you can get one for under 50.

  • I’ve found that quick release hubs and cable-actuated road disk brakes are a bad combination due to the pads running a lot closer to the disk than on MTB cable disk brakes. I think a thru-axle setup is mandatory for proper alignment. I tried running a BB7 road caliper with old 105 levers, and then a TRP Hy/Rd caliper with no improvement. I switched to Ultegra 6700 levers for more cable travel (as recommended on the internet) but there is no difference. I finally attached the cable to the “wrong” side of the caliper pinch bolt and the braking improved, but I still often have disk drag on the pads since the pads are so close to the disk. I think I need a new bike as the Softride I have has a 1″ steerer tube and there are no thru-axle forks in this size. But I love the beam!

    • Larry, I also believe (and wrote in the review above) that you should go with hydraulic rather than cable actuated disc brakes if you want to get the full benefit of what disc brakes have to offer for road cyclists. Steve

  • Steve great article and thanks for all the hard work. I’m building a Caad 12 and pairing it with RS785’s and some EC 90 SL’s. Looking for rotors and based on your article the 140’s would be fine and don’t really like the look of the bigger rotors :).
    Should I go with the RT99’s and use a adaptor or is there a comparable 6 bolt one? Bad idea going non shimano since they don’t make a bolt version for 140?
    Would rather not use a adaptor. for obvious reasons but how would RS785’s work with another rotor thats not shimano?

    • Rob, Not totally up to date on the Caad 12 but you can get the ST-R785 shifter/brake components with post mount (RS785) or flat mount (RS805) calipers. From there you can go with the Shimano 140 Ice Tech Centerlock rotors without any adapters. Check the link at the end of the post for stores that have these options in stock at the best prices. Steve

      • Steve I do have those shifter/brakes my problem is those ice tech rotors are center lock but the EC 90’s are bolt. The adapter I was talking about was for the bolt-to-center lock. I didn’t want to add any more weight than I needed to, not sure how much of a deal it is.
        Should I just use an adapter or is there a comparable bolt rotor?

  • I built a Colnago C60 disc ( black OFCG Art Deco colour scheme) just over a year ago utilising ST-R785 shifters and BR-RS785 post mount calipers with Dura Ace 9070 derailleurs and a Rotor 3D+ crankset. The braking and shifting are sublime and I simply won’t go back to rim brakes on any future build.

    I initially wanted to use a 160mm front rotor but there is no adapter available so you are stuck with. a 140mm, but my concerns were unfounded and braking, even in the hills has been just fine. I had some wheels specifically built on my favourite Hope Hubs with Sapim CX Ray spokes (32 count!) and lovely gold nipples….gergeous! The Hopes are six bolt only, so I couldn’t fit the freeza rotors and went with some Aztec 140mm six bolt. They are fine. What I do recommend though on any frame/fork with normal dropouts (not through axle) is to use DT Swiss RWS through bolts rather than normal quick release. You can get them really tight which stiffens everything up nicely and allays any fears regarding front wheel security under heavy braking.

    Just looking at my next project which is going to be titanium, I’ve researched extensively and keep coming back to Enigma….hmmmnn…so Pinarello FP3 is being rebuilt with a view to selling to fund the frame. Now, the new Dura Ace hydraulic disc Di2 is out soon….looks fantastic but yet another step up in price! I would consider the same setup as the Colnago but the BR-RS785s seem to be in short supply now. Any idea if the ST-R785s would be compatible with the new Dura Ace flat mount callipers?



    • Pete, Man it sounds like you are having fun! I’ve got the a few links up at the end of this post to the shifter/brake set ST-R785s so I’d check with those same sources if you are having a hard time finding just the brakes. As to compatibility, I’ve got to believe the ST785 shifters are going to be compatible with the DA flat mount calipers as they sell them with the RS805 brakes now. And everything across the road and mountain hydraulic disc brake lines are compatible now (the former came out of the later). You never know with Shimano until they start to ship but I’d think they’d really be foolish to start making things incompatible now. My guess is that there are some minor changes to make the materials lighter for DA branding purposes but not any brake design changes. Much of the di2 change is coming in the software and where you can put the junction box. Steve

      • I had Deore LX Trail Calipers….so have the High Powered Hose SM BH-90 Hose kit,but for £13 Dura Ace Caliper x2 & £85 x2 for new Ultegra 8000’s ,I decided to go with 785’s with Metrea Brakes as use flat Bar & wanted i-Spec II;)).
        So 785 STi shifters want be Compatible with your BH-59 Hose connections;((

  • Thanks for the reply Steve, it makes sense for them to keep to the same standard with regards brakes. It looks like flat mount is going to be the future of road disc and post mount will die out, what do you think?

    As an aside, the semi-auto shifting for optimal ratios sounds interesting with the next gen Dura Ace, which I believe comes from their mountain bike XTR di2 system but I still think the 9070 does everything I want with the ST-R785 shifters. Regarding junction box placing I got rid of the horrible rubber band for the junction A and used Sugru to attach the mount to the underside of the stem – looks much cleaner. I think I heard that Team Sky are placing it in the downtube on the Pinarello F10? And they have that bar end junction now which seams like a great idea but I guess you need a compatible bar…



  • Thanks for your article and comments. I bought my first road bike 7 years ago and spent a while before i bought. I looked around and bought a simoncini corsa with camapgnolo veloce groupset, khamsin wheels. I have covered over 17000km with two sets of wheels and now want to buy my next bike. I am looking at steel again, the tred with disc. As you say i only see good things with disc. I was interested to read your comments on trp as they supply them. I would really like sram etap with hrd discs. What crankset would you suggest? I have bepro power pedals to fit. look forward to your suggestions and links regards Vinnychoff.

    • Vinnychoff. As you’ve probably seen, I’ve got quite a few disc related posts on the site. If not, go here Carbon bikes have come a long way in the last 10 years so I’d suggest you consider a carbon road disc brake bike including some nice Italian ones. Steel could get real heavy. As you read in this post, I suggest riders go all the way to hydraulic disc so TRP’s cable disc wouldn’t be something I recommend. I’ve got and am quite happy with the Ultegra 6870 Di2 groupset and crankset. I’m testing the SRAM eTap now. Quite a bit more expensive than the Ultegra. I don’t have a well established performance opinion yet. Campy is quite late to the disc brake party. Steve

      • Steve thanks, my present steel simoncini is around 10k with accessories. i only have base campagnolo gear so not the lightest. the new frames of steel i am looking at are a total build of 6kilos. latest technology. My personal prefrence is not for carbon. I understand its the lightest but looks is also a big part for me. thanks for all your tips and help. look forward to reading more on your site

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  • Steve, have you actually tried the better cable-actuated disc brakes?

    I’d planned to bin the TRP Spyres that came on a recent road bike in favor of RS685, but abandoned that plan after the second ride. They’re good. With compressionless housing, very good, and they work with conventional levers. The pads pull from both sides and there’s enough power is enough to lock either wheel, even with stock pads and Ashima rotors. Modulation is on par with best-case rim-braking. Total weight for the Spyres paired with 105 5800 is ~860g (491g levers + 50g cables/housing + 325g calipers). Compare to (the rather hideous) RS505: ~1000g (745g levers/hoses + 260g calipers).

    The cable-actuated setup weighs less, costs less, looks better, is easier to maintain, and performs well. What’s the objection?

  • Great article. I was an early disc adopter, and still ride on Ksyrium Pro with Shimano Rs685. The stopping power is great, my issue is actuation. I want a stiff feel, but over half the levers action is used befor the rotor is contacted. I’ve bled, the bike shop has bled. Is there a shim/adapter for me? I’m looking forward to a wheel upgrade soon!

    • Tim, There’s no shim or adapter or that I know of. That’s just the amount of travel built into the 685 levers before the brakes kick in. The new Ultegra and Dura-Ace brake levers allow you to adjust this “free stroke”. I’ve written about that in the section called “Shift and Brake Throw, Adjustability and Feedback” in a recent review called Best Electronic Groupsets you can find by clicking here. Steve

      • Hi Tim (and for info Steve).

        Your RS685 brake levers are not set up properly by the sounds of it. You can adjust the free stroke and reach of the lever, which sets the ‘off’ position (the reach) which you set at a comfortable distance for your hand size. You can then adjust the free stroke, which is the amount of lever pull before the brakes are applied, which sounds like your biggest issue. Download the Shimano Dealer Manual here; and you should find the adjustments on page 62.

        I adjusted my RS785 levers and had to fiddle a bit to get the free stroke the same on both, which makes them feel fantastic, with just the amount of free play that I want. Well worth taking the time to set up properly. Good luck.

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