Are disc brakes safe for road bikes

Me, laying in a ditch with five broken ribs, after total brake failure on a curvy downhill road in Boone, NC.

Disc brakes are coming to road bikes. You don’t need to look any further than SRAM’s new hydraulic offerings as proof; they wouldn’t make it if major frame manufacturers weren’t ready to spec it. But is this progress being driven by the need for improved performance or consumer demand? And are there true performance gains to be found?

After a massive wreck thanks to disc brake failure, I went looking for answers.

What I found, outlined here and in Part 2 (wheels) and Part 3 (frames/forks, articles coming soon) might surprise you. No one seems to argue that they’re coming and that, eventually, the performance will be there. But the tone coming from the people that make the parts is cautionary. People, including me until very recently, tend to think they can look to mountain bikes’ success with discs and translate that to the road. Unfortunately, that doesn’t seem to be the case. At least not in the ultralight, super sleek package everyone’s expecting.

The biggest challenge in making disc brakes strong enough and able to withstand several miles of continuous braking is balancing weight and aesthetics with performance. Let’s face it, if they’re heavy or ugly, you’re not going to buy it.

It’s no secret that several manufacturers are working on road disc brakes. SRAM’s announced it, Magura and TRP are rumored to have something in the works, and we suspect Shimano’s not going to sit idly by. And surprisingly, Hayes has been there and done that. Because no one’s systems (or at least their specs) are official yet, we asked these brands to answer a few hypothetical questions to see how they might address these issues…

Alternative braking: Hit the side of the mountain to go from 34.8mph to 0 in no time flat.

MY DISC BRAKE FAILURE

After a solid three hour gravel road ride led by our friend Joseph from Boone Bike & Touring, we were about to wrap things up with a nice, fast descent down the smoothly paved Junaluska Road. Rolling across the top of the final crest, Evan led the way with me hot in pursuit on my Project Monstercross Moots.

Braking was handled by a first gen TRP Parabox clamping on Ashima’s new and ridiculously light Ai2 rotors. It’s important to note that the original Parabox is meant as a cyclocross brake system. The rear caliper and brake pads are smaller than the front, and the Ashima rotors are about as minimalist as you can get. In other words, they’re perfect for ‘cross where speeds are low and braking is rarely a life or death matter.

Garmin's time capture may not be ultra precise, but we all know it doesn't take long to get going fast. Blue marks the speed, green elevation.

The chart above shows elevation drop and speed. As we began our descent, it took only a few seconds to get up to speed. Being my first time on this road, I kept light pressure on the levers, dragging my brakes to keep my speed around 30mph on a very curvy, steep road. Evan was dropping me on a Canti-equipped Raleigh ‘cross bike, and I was losing Joseph, who happened to be riding the Specialized Disc Crux we have on review and maintaining a more intelligent pace.

Coming around a corner, I pulled my brakes a little harder and the levers went to the bar. I held them there. I was still accelerating. In the span of one second, I realized that a) I had no brakes, b) if I kept descending it was only going to get worse, so c) I better crash now and minimize the damage.

Fortunately, I was headed into the side of the mountain rather than off the side. As quickly as I could, I tried to push the bike out from under me and let it ghost ride. I didn’t think about what, exactly, I would do without a bike under me, but I knew I didn’t want to get tangled up in it at 35mph. That’s all I remember until I stopped, lying in a ditch in the fetal position gasping for air.

The brake fade that led to my accident is something I’ve experienced on my mountain bike on several occasions with multiple brands of brakes. The difference is, on a trail it’s easier to run off the side, skid out or drag a foot to reduce speed. There are escape routes. They may not be pleasant, but they’re not a guardrail or oncoming vehicle. Plus, most trails (other than World Cup DH courses, perhaps) are designed to break up massively fast descents with small rollers or short climbs to keep the rider’s speed in check. Lastly, you’re rarely going 30+ mph on the trail.

On the open road, there are fewer options and arguably worse obstacles. Brake fade or failure there can more easily result in serious injury or death, both due to the speeds involved and because roadies generally wear less (if any) protective gear. The descents are longer and faster. It’s worth repeating: People ride longer, faster descents all over the world every day.

Thus far, I’ve been an fervent proponent of disc brakes on road bikes. There’s still a chance my next new road bike will have them. But this experience has shed new light on some serious obstacles that need to be overcome before I’ll fully commit.

Fortunately, the Moots came out unscathed and its components escaped with minimal damage.

WHAT THE BRAKE MANUFACTURERS ARE SAYING

First, a few assumptions we’re working from: Weights will need to be low, and aesthetics will dictate a small, sleek appearance. All of which minimizes surface area to improve cooling. While DH bikes can get away with 180mm to 200mm rotors and multi-piston calipers, road bikes aren’t likely to see anything over 160mm and single piston designs.

No one wants to tip their hat as to actual product offerings, so answers here are based on the hypothetical scenario that each is or will be offering a hydraulic road brake system. No one would confirm or deny anything.

Here’s who’s talking:

  • Wayne Stetina, Shimano Road Products Specialist (U.S.)
  • Stefan Paul, Magura Bicycle Products Manager (Germany)
  • Lance Larrabee, Marketing Director for TRP (U.S.)
  • Joel Richardson, Hayes Brakes Product Manager (U.S.)

BIKERUMOR: First things first, assuming no leaks or loose parts, what causes disc brake fade or failure?

Shimano: Constant dragging can be death to brakes. Heat causes failure. The smaller the rotor, the bigger the problem. Larger diameter wheels need larger diameter rotors.

Magura: Fade on disc brakes is caused either by glazing pads (the friction coefficient is decreasing, requiring much more hand force to achieve the same brake force) and/or by overheating/boiling of hydraulic fluid, no mater if DOT or mineral oil, leading to spongy feeling and even to the possibility of a full loss of brake power, because the brake lever is touching the bar without pressure point.

Glazing pads can be avoided by following the correct bed in process and having the right compound, matching to rotor material/ surface and heat demands, which is generally already chosen by the disc brake manufacturer. So keep always with original brake pads and rotors.

Boiling oil, that is a compressible fluid, is even worse, because the brake can fail completely. This can be caused by constant dragging and/or steep gradients, pads with low friction coefficient. DOT fluid has a higher boiling point than mineral oil, but mineral oil will keep the boiling point for ever, whereas DOT attracts water over time, even through seals (and its boiling point) will decrease over time and will be worse than with mineral oil. That’s also the reason why brake fluid on cars has to be changed every 2 years.

Having big heat dissipating surfaces is good. Small compact surfaces generate heat build up.

TRP: Heat is the number one cause, whether it’s cars or motorcycles or bikes. And I think there’s potential to get them hotter on the road.

BIKERUMOR: In a nutshell, how do you prevent brake fade or failure?

Shimano: You either get a bigger rotor with metallic pads which can operate at higher temperatures, or you get something like our IceTech that can keep cooler for longer and dissipate heat better and quicker. Even the aluminum flanges on our CenterLock rotors is going to dissipate heat better than a one-piece steel rotor.

Magura: Choosing the right friction parameters of pad/rotor, use original parts, avoid drag braking (short hard braking is better for recovery in between), use big rotors (hand force and pressure to the pads will decrease, thus thermal load).

TRP: You want to have a rotor that’s designed to remove the gasses formed by the pads heating up. Good airflow through the brake will keep it cool. And the last thing you want is for the caliper to get so hot that it vaporizes the fluid. If the heat transfers too much to the caliper, it can boil the liquid.

There's still plenty of pad material left after the wreck. The Parabox comes stock with semi-metallic pads.

BIKERUMOR: More specifically to road bikes, what are the key design differences you had to consider versus your mountain bike brakes?

Shimano: When you take the braking surface off the rim on a mountain bike, you can reduce material there and weight. I don’t believe we can do that on a road bike. If you eliminate the brake surface on a road bike and reduce material, I think you’re going to make it too fragile. It would be unable to maintain its stability.

Weight is more critical. The brake system itself isn’t so much the problem as redesigning the frames for the different torsional loads and redesigning the front wheel to accommodate for the asymmetrical dish. Radial lacing designs won’t work, I think the wheel manufacturers have a bigger challenge than the brakes manufacturers.

It’s not a design difference, but initial designs might be limited because of the upfront investment needed to produce something that may have a limited audience and limited number of frames capable of using them. So the initial cost difference between standard brakes and hydraulic disc brakes might be more than people are expecting. I was told the cost of our original Di2 prototypes were around $30,000 each, so when you really start getting into considering production, you want to minimize the number of prototypes you have to go through. We’re studying this very hard.

Magura: We’re only offering hydraulic RIM brakes for TT and Tri-bikes (at least at the moment, brakes for normal road bikes might follow!?!), no disc brakes. Hydraulic rim brakes are lighter than disc brakes if you look at the complete system. The brakes itself might be equal, but forks and frames for disc brakes have to be beafier and made stiffer to take the loads from disc brakes with their asymmetrical force input. The system of road frame and fork for discs is minimum 500gr heavier than for rim brakes. Weight on disc brakes depends also a lot on the rotor size, the bigger the rotor, the more weight. In order to achieve high heat loads on disc brakes, especially on longer, steeper descents, bigger rotors are neccessary, at least 180mm front, increasing the weight additionally. Rim brakes are more aerodynamic than disc brakes, they can be hidden in the same shape as frame and fork, Disc brake calipers and rotors always protrude the shape of frame and fork.

With rim brakes you already have the biggest possible rotor on a wheel: the rim!

Rim brakes don’t suffer from heat build up/overheating on the hydraulic system, as the distance friction partners (rim/pad) is really far away from the hydraulic piston, so no expansion chamber is even neccessary.

TRP: We’ve done a lot of testing with the Parabox knowing that what started on the ‘cross bikes is moving to the road. With our new system, we’re going with a larger caliper on the rear and we’re recommending everyone use a 160mm rotor on the rear. We’ve cut out some material, but we’re making sure there’s enough material on the rotor to give you both stopping power and enough heat dissipation.

We had to develop it to handle the additional heat that will accumulate on long descents. With road bikes you’re on the brakes for longer period of time and there’s a lot of stress. The amount of grip on road bike tires is more than what most people think, so you do need big powerful brakes. I’ve experimented with a 180mm rotor on the front and it’s nice. Compared to mountain bikes, the piston and rotor sizes are quite similar from what we’ve found.

Ashima's minimalist Ai2 rotors might be great for cyclocross and lightweight XC, but perhaps not for road. Massive discoloration shows how hot my rotors became, they were silver at the ride's start.

BIKERUMOR: Will pad compound or rotor surface materials need to change? Which of the two is more important on the road?

Shimano: No. Generally because the bikes are heavier and the grades are steeper, you would expect there would be less heat build up issues on a road bike. I think technique will help too, riders may need to brake hard for a short distance, for instance coming into and going around the corners, then let off so they can cool. I think in your situation, you were on the brakes the whole time and they simply got too hot. Metallic pads are going to be noisier and take a little longer to warm up, but they’ll work better once things get hot. With IceTech, though, we were able to put resin pads under riders that were previously needing metallic pads and give them better, quieter performance just because they system cooled so much better.

Magura: Pad compound and rotor surface on MTB disc brakes is already on the top. If we had better friction partners, we would use it on both MTB and road.

TRP: We’re not exploring any changes in pad compounds or rotor materials, it’s more about rotor shapes to disperse the heat. The pads in the Parabox are semi-metallic and that’s what we’ll likely stick with.

BIKERUMOR: What about rotor or caliper shape, or pad size – can those dramatically improve performance?

Shimano: They all impact it, and everyone has their own strategy to get the lightest most powerful brake that won’t overheat and still do the job. If you look at race motorcycles or high performance cars, you get multiple pistons or one large one. When you add pistons, you get more twisting of the caliper, which means you need a bigger stronger caliper and rotor. A longer, thinner brake pad will give it more surface contact and friction. It’ll also give you more area to dissipate the heat, and the caliper can be made stiffer. For your size, you might want 180mm rotors and IceTech rotors. Under the same conditions, our IceTech system can run up to 50º cooler.

Magura: Shape and size is already on the optimum for the actual moment on MTB disc brakes. Using the same parameters on road brakes will give better performance on road disc brakes, as the average speeds are higher than on MTB, giving a better cooling effect/better heat transfer into the surounding air.

Increasing pad size would increase weight again (more material of the pad itself and on the caliper to take the volume of the increased pad).

TRP: There will be some new road specific designs, all in the interest of better performance but also in terms of appearance. It’s got to look a little more subtle, and ours will be sleeker than our mountain bike calipers. We’re experimenting with different piston materials and shaping the caliper body to get more airflow through there and radiate the heat better.

BIKERUMOR: Mechanical versus hydraulic discs for road, any performance or safety difference with regards to brake fade?

Shimano: There’s absolutely no difference in brake fade. The benefit to hydraulics is better modulation, there’s a more linear progression of braking power. Plus, the hose won’t get contaminated like cables and housing.

Magura: Mechanical disc brakes will not suffer from boiling oil, but from melting of other components, spongy feeling and bad modulation from mechanical cable and housing. If mechanical disc brakes would be top, then MTBs and cars still would use them!

TRP: You don’t have the fluid issue, but I don’t know that one might be better than the other. You can develop more power with a hydraulic system, and the calipers will compensate for wear, but you have the potential to boil the fluid.

BIKERUMOR: Set up is going to be key. What can you do to ensure OEM spec’d bikes are set up properly, particularly with hydraulic disc brakes whose lines run inside the frame, requiring them to be disassembled and bled prior to the sale?

Shimano: You keep seeing evolution of things where we have the one-way bleed for our mountain bike brakes that makes it virtually impossible for air bubbles to get trapped. Once it goes to the factory, it’s out of our hands. It’s got to be the dealer that’s properly trained to assemble and tune the bike before it gets into the consumers’ hands. All of our systems are sent to the OEM manufacturer pre-bled and are installed. Once they start running hoses inside the frames, it’s going to be a colossal pain in the ass. I think the potential for routing hydraulic brakes internally is not so great because of the one by one labor that would be involved. I don’t know if I’d want that. I guess you could develop joints, like a banjo joint, that could be mounted on the entry and exit points on the frame.

Magura: All Magura brakes, also our RT rim brakes are already designed with service in mind. We use the same tools as on any other of our hydraulic Magura brakes, we use the same Royal Blood mineral oil, we teach our OEM customers how to route lines, how to service, how to assemble. The same we are doing already on the MTB range brakes.

TRP: Every single brake that comes from our factory is cycled 300 times, pressure tested, held for 36 hours, then pressure tested again. Of course, when you start running this inside a frame, that all changes. We’re working on a system that allows you to maintain the pressure in the system while disconnecting the hose. This will allow you run the hose inside a frame without losing pressure (Editor’s note: this is very exciting!).

BIKERUMOR: And for aftermarket sales?

Shimano: You want to take it to a shop that has a lot of experience with mountain bike brakes. Shimano does a lot of hands on training by our traveling tech reps and has online training for dealers. All of this helps ensure they’re set up correctly, and it’s pretty easy to tell if they’re working properly.

Magura: We always recommend: RTFM! (read the f…. manual!). Our manuals always come with detailed installation guidelines. If you follow them, you´ll be fine, even without bleeding. And if you need to service/bleed the brakes, we offer service kits with Royal Blood mineral oil.

TRP: Like our mountain bike brakes, you’ll need a bleed kit if you need to trim the hose. But our new system we’re working on will simplify that process quite a bit.

BIKERUMOR: What about the bike frames themselves?

Shimano: Frames will have to be beefed up to handle the different torsional loads, particularly on the forks. If you just take a fork that’s developed for rim brakes and add disc mounts, that fork is not prepared to take the braking force on one side down at the end. And the rear spacing will have to change to 135mm. It’s a big deal. The other thing that people don’t think about is that you have to offset the front wheel. To handle the narrower spoke flange width, you’re going to either have to add four spokes to the front wheel or about 40g to the rim to make it strong enough. And you won’t be able to use certain types of spokes, meaning it’s not going to be as aerodynamic. As for material, a carbon frame isn’t going to dissipate heat from the caliper any.

Magura: (Answered above)

TRP: Like everything else, manufacturers have taken material away where it wasn’t needed and added it where it was. With carbon fiber, it’s pretty easy to figure out where it needs to be stronger and make it so. You’ll see wheel and hub manufacturers do some interesting things like bigger and thru-axles. Specialized is already aiming their dropouts slightly backwards to keep the brakes’ rotational forces from throwing the wheel out.

And then I talked to Hayes Brakes product manager Joel Richardson. Most people don’t associate Hayes with road bikes, but it turns out they may just have more experience with road bike disc brakes than anyone at the moment:

“About six years ago, we identified the road market as a very good application for disc brakes at a high level,” Richardson says. “We spent a good amount of R&D time and money to develop hydraulic and mechanical disc brakes for a major OEM manufacturer, one of the biggest. After a couple years of development, we hit major roadblocks. The biggest of which is packaging. The current mountain bike brake designs and mounting standards -six bolt rotors, flange offsets, 74mm direct post mount, etc.- just didn’t work for road. All of these were done for a reason with mountain bikes and they work there. The road we went down was a new standard for mounting the brakes. We were working with a major player in the road bike market, but even with their substantial clout, we found that the required packaging of the product didn’t mesh with what customers are likely to want (read: buy).

“What we found with road bikes was that you can generate incredible heat and forces. There are long descents where you’re dragging the brakes for a long time. You have tiny little calipers with very little thermal mass. And they have tiny little pistons that require very little fluid volume. Then you have tiny rotors with virtually no mass that can’t dissipate heat. When you whittle everything down to a super lightweight package, the only place for all that heat to go is the hydraulic fluid, and you can boil it in no time at all. When the fluid boils, it happens instantaneously and it happens right behind the brake pads. As soon as that happens, it introduces air into the system.

“Another thing people don’t think about is, even though they’re skinny, a grippy road bike tire on hot pavement can create a tremendous amount of torque at the rotor and caliper. It’s much easier to lock up a mountain bike tire on a loose surface than it is to lock up a road tire in good conditions, and that puts more friction between the rotor and caliper when braking, and that means more heat.

“The idea has merit and can definitely be executed. We believe in it and know it’ll happen. We’ve built dyno and real world tests around it and spent considerable resources to explore it. At this time, we’re primarily focused on mountain bikes. We have a mechanical road caliper, the CX5, but, well, we don’t have shifters for the road. So here we are.”

will disc brakes on road bikes be able to handle the heat

Tread marks from my cyclocross tires as the bike slid off on its own.

I want to point out that I installed the parts myself, cut the rear hose and re-bled the rear brake and chose to not use TRP’s stock rotors. I do not blame TRP or any other manufacturer for what happened. In hindsight, it was poor parts selection for the actual use. And perhaps I could have used better braking technique – brake hard, release, brake hard, release.

That said, I think it’s not unreasonable to assume most roadies will choose similarly lightweight parts without knowing the performance capabilities and limitations, and many will drag their brakes to limit speed. In the end, all I know is heat was the culprit, but what the exact technical consequences of that heat were on my equipment is unknown other than it failed. And for most riders, that’s all there is to care about.

Stay tuned for discussions with wheel and frame/fork manufacturers over the coming weeks.

Big thanks to Johnny R. for stopping and calling 911, and to Boone’s fire rescue, EMT’s and doctors that took great care of me!

Note: SRAM was invited to participate but has not returned answers as of publishing, which is a shame because they’re the only ones with a publicly announced system. Perhaps they’re keeping quiet until the official launch. If we hear back, we’ll update the post.

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153 Comments
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will
9 years ago

i read this article twice in the hopes that one of these three representatives could prove beyond the shadow of a doubt as to why road disc brakes are superior to caliper brakes. all the questions that were asked are all very valid and important questions. in my opinion, not one answer given justifies the cost, the weight, the potential danger, the headaches for the shops, frame aesthetics. we all know mtb disc brakes are superior than mechanical and linear pull for mtb. no question about that. but road brakes and road braking are completely different than mtb. keep discs for mtb and cross and leave them off road bikes.

satisFACTORYrider
9 years ago

nice read. glad you’re ok. i can see having to design frames and components to accomodate stronger braking forces. pad adjust and return need to be sorted out as well as the heating issues. time to install an abs next to di2!

Steve M
Steve M
9 years ago

Based on the reliability of some of the disc brakes i have used over the years? No thanks. Car and motorcycle brakes are ridiculously reliable. Bike brakes? not nearly. The brake makers are really going to have to deal with the light weight vs. dirability issues. It is not acceptable to have one fail. I run Maguras on my mountain bike and they have been the best. No aftermarket pads, rotors, or bolts thank you very much.

Nice article.

gee
gee
9 years ago

that was probably one of the more impressive write ups, glad you are OK, thank you for some sound journalism.

harro
harro
9 years ago

great article guys, very insightful

off-roadie
off-roadie
9 years ago

Glad to see a post like this. It seems like everyone is crazy about getting hydraulic disc brakes on their road bike without considering if they are even a good idea. Glad you’re ok, good post.

hooby
hooby
9 years ago

i can’t believe how level headed you are about this episode – that sounds like a horrible experience! And you’re still open minded wrt disk brakes! Personally, I think I’ll hold off for a while before I jump in with the innovators on this one. Great write up.

Dusty
Dusty
9 years ago

Glad you’re OK!
My new road / touring bike has Avid BB7 road calipers (mech) and 160mm discs front and rear mated to 105 levers. I ride in the city, often in inclement weather so I definitely like being able to brake in the snow / rain, which also seems to be the time that many drivers forget how to operate their vehicles.
I haven’t had it out on any big rides yet, but I’ll let you know if they exhibit any problems, (provided I can still type after the carbon fork snaps in half ha ha!)
OK, that’s not funny…

pantsandjacket
pantsandjacket
9 years ago

Wow, that rotor is cooked!

Jon
Jon
9 years ago

Glad to hear you came out of your crash okay. Thanks for the well-researched write-up. While I’ve no interest in hydraulic brakes for my road bike due to their negligible performance benefit for my riding applications, it’s good to see what manufacturers are doing with the technology.

Whatever
Whatever
9 years ago

This is actually the first non-PR, and insightful post on BR. Perhaps you are rising a little above my current mental bookmarking as the TMZ of bikes.

That said, I really do think your brake failure is your fault. Have you ridden carbon rims with cork pads? Then you really know brake fade and brake loss. And heat problems. There is no reason your should have allowed yourself to lose both front and rear.

Discs done well on road will actually lead to better road rims. And I’m always happier to be bombing a descent on the MTB vs. the roadie. I think the real cause of you problem is how you set the shimano mechanical to TRP liquid linkage. Funny there are no post of this.

Brendan
Brendan
9 years ago

First off, sorry to hear about your accident. Second, way to turn a negative experience into a topic for a very insightful post. Keep up the good work, and get better soon!

aint skeerd
aint skeerd
9 years ago

Sounds to me like you where riding like a p****, Come on if you ride down hill like that on a rim break you are going to have issues, I ride my mountain bike down maountain paved road reach 45mph and have never had any issues.

ajh
ajh
9 years ago

I am glad that nothing worse happened as I see that big rock on the side of the road and am cringing what would have happened if you hit your head on that.

On the subject itself I see the early benefits to those that are doing cross as some wet/mud rides can make brakes basically useless. On the other side of this when the brakes are useless it is usually conditions that if you actually had brakes you would slide out and crash anyway. We also have to be careful as I know, like me, many use a cross bike on the road and may find issues such as yours if not informed.

In the long term I believe that we will have to adopt a lot of changes for disc to transition properly to road. This will be very interesting times and I hope that it is standardized, unlike BB’s today, so that we are not having to change half a bike after deciding to change one part.

Atgani
Atgani
9 years ago

Whatever

Great to see that having no insight into the situation doesn’t disbar you from passing comment…

I have the impression that Tyler is both knowledgable himself and has knowledgable friends

If there was a “botched” installation, which I doubt, I think his riding buddies may have spotted this

I’m sure that Tyler is grateful for you pointing out it was likely to have been his fault

Can I sign up for your braking masterclass, or are you to busy as a troll?

http://en.wikipedia.org/wiki/Troll_(Internet)

Gordo
9 years ago

I am using Avid road BB7’s and have not had any problems but have not dragged them for an extended period of time. I do agree that modern cars and motorcycles all have hydraulics but they also have motors so I doubt any of them are under built and boil up the fluid. My mechanical BB7’s are not as nice feeling as hydraulics but with no fluid to boil, I don’t see where they could fail on me other then wearing out the pads or warping the rotor. I do agree they are not sleek looking and are a bit heavy but they seem up to the task. Great article and glad you are ok. Cheers, Gordo

Louis
Louis
9 years ago

Great article. I think that a lot of the time cyclists, roadies in particular, get really worked up about having the latest and the greatest without really asking why. Do we really even need discs? I can see it being a better option than carbon rim/cork pad braking, but surely it would just be better to go back to metal brake tracks versus the extra complication that comes with a hydraulic system.

Personally, I’m a terrible mechanic. Its not that I can’t do all the stuff needed to keep my bike in working order, I just prefer to not have to do it. I grab a bike and go for a ride. And for the most part this works for me, not cleaning my chain probably won’t kill me. Hell, I can even get away with a few psi below perfect. But it would suck to introduce “bleed or die” into my pre-ride routine.

For now, my bikes remain high end cable actuated shifters and brakes and ultralight aluminum rims (carbon/aluminum for racing). I just don’t think I give up that much by not being on the cutting edge of cycling technology.

Mindless
Mindless
9 years ago

Luddites are doing it wrong.

Use normal rotor, not this crap.

Topmounter
Topmounter
9 years ago

I live in Colorado and have been riding discs on my mountain bikes for five or so years now. We have plenty of extended, fast and windy descents on pavement, gravel and/or trail. Throughout my 20 years of road and mountain biking with rim brakes (cantis, calipers and v-brakes), I’ve had cables snap, pads fail and a couple rims collapse catastrophically due to a failure of the braking surface. To date, I’ve found disc brakes to be just as, if not more reliable and more predictable than what I’ve experienced with rim brakes (especially when riding in and out of wet conditions).

Regardless of whether you’re riding rim or disc brakes, paying attention to lever travel, braking power, brake fade, odd noises, pad wear and any other tell-tale signs that your brakes may need maintenance or are at their performance limits is always key (the same goes for tires of course).

For the sorts of road riding I typically do, typically a combination of smooth pavement, broken pavement and gravel, steep descents (usually gravel) and unpredictable wet conditions (e.g. afternoon showers or snow melt), I’m looking forward to having the power and modulation of disc brakes on my road bike… of course I won’t be shaving grams by using minimalist calipers and teeny-tiny rotors to impress the coffee shop crowd.

Steve
9 years ago

I’ll probably get flamed for this but…you were using an adapter to make cable brake levers with really, really light rotors. My response reading this was…”not surprised.”

I do not see how insightful this article is with regard to “road disc brakes.” You were not riding “road disc brakes.” When you do, and report on them, I can then see how that report would be insightful to “road disc brakes.”

Mountain disc brakes work just fine under those conditions.

Plenty of folks run BB7s on touring bikes and tandems and log longer descents with much more weight. They do not seem to have the problem you had. Seems like the system let you down…not “road disc brakes.”

dgaddis
9 years ago

Great post.

ajbosch
ajbosch
9 years ago

Great read, glad you came through “relatively” unscathed.

A question though? What is the increase in speed AFTER the fall though?

Eckeecke
Eckeecke
9 years ago


Did both of your brakes fail at the same time? Usually only fails first, but if you keep both dragging than it obviously can happen.
Otherwise a very well written and informative article!

JeroenK
JeroenK
9 years ago

Glad you are OK now.

I just do not see in what way this crash provides an answer to the ‘will they work’ question. You have said it all in the second to last paragraph.

**No one is safe with poor parts selection or braking technique.**

There have been accounts of inner tube explosions due to heated up rims, because of brake dragging. There have been cases of brake cable bolts not tight enough. You can get a really wrong brake pad / rim material match with rim brakes too…

I am really sorry, but this story should be a warning to all DIY mechanics above all. The only real risk is roadie mechanics thinking they know what they are doing. It’s all new technology and it’s brakes. Be careful and follow manufacturers’ instructions.

FHS, we all run disc brakes in our cars. The concept is fine.

Vodalous
Vodalous
9 years ago

So, did you try jammin your foot between the frame and the front or rear wheel to slow down (ala brakeless bmx)?

I wouldn’t hesitate to put disc brakes on my road bike. I feel unsafe on my road bike because even with the brakes dialed in, it just takes to much effort and to much distance to stop in an emergency (stupid pedestrians). With my single speed mountain bike with big old slicks I can come to a stop within a few short feet. Thats critical when your commuting acrosss town in heavy traffic.

The other reason I wouldn’t hesitate to install disc brakes is because I don’t worry about over heating. I go fast on my road bike, that’s the point. I don’t hit the brakes on descents, I just scrub a little speed into a corner and hold on. I think for the advanced rider disc brakes have a lot of potential.

mountguitars
mountguitars
9 years ago

awesome article! opened my eyes to how disk brakes are so different between road and MTB. i rode MTB most of my life. i understand the braking technique needed to keep the brakes cool. another thing that could’ve prevented your accident though were the rotors. i’d stay away from ashima’s lightweight rotors. currently, i have the aerotors on the rear of my XC bike, but in the front, i had to change it to something with more surface for the brake pads to grab a hold of (shimano XT 6-bolt rotors). on the aerotors, braking power was strong but modulation sucks, IMO. plus, it ate up my pads very quickly. brake fade? yes! but i replaced only the front since i use my front brakes most of the times vs the rear. you were even using the 2nd incarnation of the aerotors. that even made worse, i think. but hey, its great to know your ok and doing this article opens up a lot of things.

Ralph
Ralph
9 years ago

Glad you’re ok!

I live in Boone and have ridden that section of road many times. Just so the other readers know, this hill is incredibly steep and unforgiving (sorry, don’t know the actual %). There’s little room for doing on/off braking and it’s virtually impossible to completely let the brakes off given the steepness and curvature of the road. Waiting to brake on this section of road could overwhelm the brakes, as a hairpin turn awaits near the end. I often descend this road on my disc-equipped mtb. In the years I’ve ridden disc brakes, the only time I’ve had my discs heat/expand to the point of becoming completely locked is on the rear brake on this descent (it’s happened different times with different disc brakes–all with DOT fluid). It’s never happened to me during any trail riding under any conditions.

I’m not saying there might not have been set-up issues, but we should also take into consideration this specific section of road (not very long, but very steep and needing fairly constant braking) and the unique circumstances it (and likely others) present for some disc applications.

black dragon
black dragon
9 years ago

Glad you’re still alive.

Maybe you need next time a carbon composite rotor like the Formula 1 cars 😉

The Dude
The Dude
9 years ago

Great article and well written. Glad you are OK. Now go buy new rotors.

Brian Van
9 years ago

I’m sorry that this accident happened to you. I don’t mean to pile on about any errors that may have occurred, but I want to say something to the audience about good braking technique because someone could get hurt if they’re doing the wrong thing:

First off, NEVER DRAG YOUR BRAKES ON A HILL. It literally makes your brakes much weaker at the moment when you need them the most. Even rim brakes are likely to suffer performance loss in that scenario, and you risk serious injury or death.

The proper road braking technique for slowing or stopping over long distances, without exception, is to pump them in short bursts. Grip firmly then release briefly, repeat.

Also, know your equipment very well and don’t make unfortunate discoveries about its limitations on ride day. Test it out in areas where you face little risk from unnecessary hazards – do seemingly tedious things like accelerate to 25mph and test your road bicycle’s full-stop abilities. And in everyday usage, use your testing knowledge and don’t take risks that your equipment cannot handle. If you notice that your brakes are a bit weak and it’s difficult to come to a stop at 35mph on a downhill, then don’t ride at 35mph downhill… begin feathering your brakes at 25mph and don’t exceed that velocity by much. Be proactive in keeping speed manageable, before it’s out of your hands.

It’s basic physics: momentum is the square of velocity, which means that extra 10mph in velocity means a LOT of extra momentum – more than double. The extra speed counts more than you think. You can quite suddenly be in an unsafe situation if you exceed the operating limits of your brakes.

Tyler was fortunate and smart to test his brakes in an area where he could minimize his risk from crashing. Perhaps all that you could do better (other than using the correct braking technique and using the best-quality gear) is to attempt this in a pillow factory.

—–

Also, I think I’m gonna stick with my rim brakes for a while.

Sean
Sean
9 years ago

As a Mt. biker that gave road biking a try, I never understood why hydraulic disc brakes hadn’t been adapted to road bikes. This article has raised a lot of points that I hadn’t considered. Thanks for this enlightening information.

mike
mike
9 years ago

i’ve had my BB7s down some really steep road descents with long hard braking…NP. don’t see the attraction of hydros. and rim brakes are worse…melting tubes, popping tires, just another way to break ribs. good write-up.

AlexK.
AlexK.
9 years ago

Tyler choose a ridiculously lightweight setup and then acted surprised when it failed. A couple hundred grams in weight would have alleviated all your issues:
-I use bb7 road calipers and hit 40+ regularly. All this with 160mm rotors. The brakes aren’t the issue.
-Use a bigger rotor. The weight increase is trivial and the increase in stopping power is noticeable. Of all the places you don’t want to skimp on material – the brake rotor.
-I’m surprised to hear that you didn’t have your wheel radially laced as well.

This article is ridiculously biased. Learn to brake properly or buy components that compensate for your ignorance.

Steve
9 years ago

AlexK. FTW!

Gillis
Gillis
9 years ago

I think one of the problems I’m seeing is the weight issue. Mtb’ers are way more tolerant of heavier parts if the performance gain is there. Canti’s are lighter than discs but we know the braking would suffer tremendously, so we accept the weight penalty readily. That was the case just switching to linear pull brakes (V-brakes). And there was a time even when discs became the market standard that xc racer dudes were still using V-brakes simply because they were lighter. Eventually the weight came down somewhat and they saw the benefit of better braking (that or their sponsors forced it on them).

I can see the road market is going to experience a similar trend. The high end and pros won’t toucdsh it until the 2nd or 3rd generation once all the kinks are worked out and weight comes down. Because the 1st gen is going to be heavier, maybe not work like every one expects them too. The road market doesn’t see as much innovation/experimentation in drivetrain/brakes/etc. Which is why the industry is working so hard to get it right the first time.

All the problems posed above are just problems that will be solved. It’s what engineers are for, its what they do. It’s not a reason to shelve it. I think Hayes problem was that while they identified the market, the market hadn’t been asking for it so the costs couldn’t be justified. I think it’s in a better position to do it now.

dan
dan
9 years ago

“disc brakes will never take off on mountain bikes. why bother when there is already a brake surface there? Added weight, added pain and weaker wheels when V-brakes work so sell. Never gonna be used outside of a few nut job DH riders”
my boss and owner of a bike shop/bike company in 1995.
there are a lot of problems with disc on a road bike, but the potential for cool aero designs in a few years seem worth it.
just sayin’ is all…

Greg
Greg
9 years ago

I think this article is well written and as someone else mentioned, very level headed given that he broke 5 ribs. I also think its ignorant for many of you to write in that this is user error given that Tyler is an editor/creator of a bike website, its safe to assume he can ride a bike and has lots of experience on bikes. (plus I’m tired of people writing in how they are better riders and don’t have these problems)

Tyler, I like how you have actual data and pics to show for the incident. (not “just riding along”)
I think all manufacturers should read this article as a note of caution. He was descending for less than 3 minutes when he bailed and going over 30MPH. That’s not dragging the brakes for 10 minutes or something extreme and also demonstrates the grade of the descent.

superleggera
superleggera
9 years ago

Although the costs to do it are expensive (it’s a time consuming process given the manufacturing method) — it won’t be long before you see carbonfiber rotors being utilized. We use on all the racecars and racing motorcycles for a reason — the hotter it gets the better it works. Very light and smaller then a regular rotor setup. Negative is cold modulation but still probably better than existing setups.

Looking at the rotors you used that were so radically lightened — I’m not surprised by the results you experienced.

The biggest problem with disc brakes on a road wheel is the contact patch (tire) to the ground -vs- modulation of the brake itself. It’s just a much easier equation for a mtnbike setup.

Matt
Matt
9 years ago

AlexK, while I agree with you that the lightweight setup for this article was a big part of the failure issue, you are also comparing bb7 MECHANICAL brakes to hydraulic brakes. The failure point on hydros will most likely be from overheating the fluid to the point of vaporization which will render the brake useless. You won’t ever get this in a mechanical.

Tyler was already using a 160mm rotor (Ashima Ai2 only come in 160mm and 180mm) but it is highly carved out to shave weight. A less lightweight rotor (with more surface area to dissipate heat) may have helped but I don’t think anyone can say it would have solved that problem. TRP even admitted their new Parabox system has changed to accommodate the added heat for longer road descents – “With our new system, we’re going with a larger caliper on the rear and we’re recommending everyone use a 160mm rotor on the rear. We’ve cut out some material, but we’re making sure there’s enough material on the rotor to give you both stopping power and enough heat dissipation.”

ezweave
ezweave
9 years ago

I started riding MTB seriously in 1998 (as a teenager) and having experienced the transition from early disc brakes (Rock Shox had some notoriously bad ‘cable actuated hydraulic’ models) to Hayes domination around 2000. Which is to say, I’ve put in serious off road miles on discs in the last twelve years, from winding
and rolling mountain trail rides, to shuttle or lift driven downhill.

It seems like this was a combination of lightweight gear and, perhaps, riding the lever (as has been pointed out).

This has been said, but I think people should realize this isn’t some “I can ride better than you” reaction… it’s a real problem that you end up learning to combat. No brake works well when ridden… that’s just simple thermodynamics. Even my Ultegra calipers on my road bike will have issues on long mountain descents where I notice that it takes more force to stop. You cannot drag any pad constantly, the surface and the pad need time to cool. After all, friction generates heat (all that energy has to go somewhere).

Early on, when I finally could afford a real down hill bike, I learned this the hard way after setting a pair of HFX-9 pads on fire (and to be fair, the brakes still worked enough to keep me from crashing) after a twenty mile downhill ride with a good steep and sharp, technical descent for the last few miles. I had learned to pulse my v-brakes years before (v-brakes have the same friction issues, you only mitigate it slightly by having a thick rim to suck up heat) and had not applied the same techniques to DH riding with “super awesome” brakes.

Oops.

The real problem with disc brakes on road bikes has been one of marketing and weight: competitive road riders are obsessed with light weight and (sometimes) sexy gear (this is a slippery slope as I personally find much of the “sexy” gear ugly and impractical). After all, motorcycles and automobiles use disc systems and do not have these issues (unless you don’t downshift on long descents… I life in CO and the smell of burning brakes from ski commuters in Summit County is a sign of ignorance, not of the failure of brake design).

Also, there is some seriously poor notional general physics in these follow ups. Momentum is mass times velocity. Acceleration is the change in velocity per square unit time. I don’t know how you could mess up p = mv or F = ma, but hey it probably sounds good in the bar.

Steve
9 years ago

It was NOT a hydraulic brake. It was a cable actuated HYDRAULIC ADAPTER designed for CROSS. Not the same. Apples and oranges.
It is ignorant to believe this post in any way reflects what is happening with “road disc brakes.” No “road disc brakes” were used.

David
David
9 years ago

Glad you are ok now. Thanks for a very insightful write up. The Manufacturers responses were helpful and while I have no doubt it will someday happen, I just cannot see a need when we already have the best rotor size and heat sink already holding onto the rubber… Perhaps the rush to get more carbon into our wheels to reduce rolling weight is part of the demand? Carbon wheels are a lousy brake rotor. Perhaps as carbon fiber (and whatever else comes along) wheels get lighter and stronger a point will be reached where all the parts as a whole will qualify for a large light rotor and caliper system that will work in the manner that road riders are inherently used to applying their brakes (and competition will dictate) in an aero design that won’t compromise speed.

Gillis
Gillis
9 years ago

I think a lot of you are missing the point in blaming Tyler for his accident or as comparison for hydraulic road brakes. The key thing is that his accident sparked the question:

What are the problems faced in designing a hydraulic disc brake system for road bikes?

Nothing more nothing less. And he went about it in a very respectable way by contacting specialists in the industry.

shabbis
shabbis
9 years ago

I agree with mike, I have BB7s (160 front and rear) along with Gore Ride-on sealed cables (as must) on my cyclo-commuter and commute in a very hilly area. While the BB7s do require more maintenance to keep them running smoothly, I find the increased performance worth it, especially in the rain. I have a very steep paved road which I descend on my way home from work everyday, after riding my cyclo with BB7s and my old six13 with DA 7800 rim brakes, I’ll stick with the BB7s, especially in the rain. I also apply the disc technique of brake, release, brake, release instead of just sitting on them the entire time. I’ve also stuck with the stock pads and rotors. I would think mechanical discs would be plenty for road and that they should just focus on improving the cooling technology.

SL
SL
9 years ago

Rough bail, hopefully you’re doing a bit better now and not off the bike for too long.

As a mountain biker who’s actually waiting for road disc brakes to become available/mainstream (proper ones, none of this Parabox garbage), it’s interesting to realize that the forces and speeds you can reach on a road bike are able to completely boil brake fluid. It hadn’t even occurred to me that this might be possible. But then it should have, I’ve completely roasted an Avid Code on Whistler. That wasn’t very fun…

As with mountain bikes, there’s going to be an inevitable period of adjustment and rapid technological change when hydraulic discs finally hit the road market hard. Lessons will be learned, gear will improve, and standards will come into play. Will weight continue to be an issue? Sure, but they’ll get there and besides, pros’ race bikes need to hit UCI minimum weight anyways, so why not slap some Shimano discs with Ice Tech rotors and radiator brake pads onto a carbon frame? They’d lower the CG a bit and might help with rotating weight. Add better modulation and all-weather braking to the mix and I still think hydro discs are the way forward for road bikes. On the other hand, it’s entirely possible that hydraulics will introduce significantly higher downhill speeds, which may not result in more crashes, but rather much more severe ones.

One thing’s for sure: 160mm + rotors, none of the ultra light ones. I run 200mm rotors on all of my bikes and it seems like a trend I’ll continue on my future road bike.

stack
9 years ago

I did the same ride as you guys 2-3 hours later that day, and heard about your crash. I want to reiterate to the other readers that road is easily the most technical and difficult descent in the High Country. After years of expounding that all road bikes would have discs one day, this article has really made me question my hubris. Extremely good stuff. Hopefully, I can tag along next time you are up here.

when
when
9 years ago

I also have cable-actuated BB7s on my road bike. I’ve descended several miles of 10% to the point where the plastic covers on the caliper adjustment knobs melted, but the brakes themselves had no issues. Hydraulics IMHO will have issues with long descents but cable-actuated do not.

Bog
Bog
9 years ago

There are many good comments but it seems that everyone here is missing a big part of the puzzle. Not only was Tyler on his CX bike, he was riding with CX tires. In my experience you NEED to drag the brakes more than you would with real road tires because you’ll drift like crazy if you don’t control your speed. With road tires you can carry far more speed through corners and brakes in bursts.\

That being said, I’ve been using disc brakes on my mountain bikes for years and we have more than our fair share of wickedly long descents in the Vancouver area. I’m 240 lbs and many times I’m on the brakes for minutes at a time trying to control my speed and have never lost my brakes. I’ve witnessed brake fade with lightweight rotors so I only use “real” rotors such as any of the models that Shimano makes. They may be a bit heavier but they’re actually designed to handle real world braking unlike some of the lightweight jobbies.

Mindless
Mindless
9 years ago

I often do 3K+ descends on my mountain bikes, and with a proper setup (I use Formula and Shimano brakes) – there is no fade, there is great modulation, and there is excellent reliability. In the days of V-brakes it sucked.

2012 XT with finned pads have NO fade.

You drag on some really useless rotors and use some poor brakes and act surprised when it is not working.

Disk brakes are much better then calipers. Wait until you can use some disk specific rims – that are wider, lighter and stiffer – then compare system performance.

Bad and misguided article.