# Disc brakes needed for carbon wheels?



## onespeedbiker (May 28, 2007)

According to Bicycling, disc brakes are going to start showing up on more road bikes in the near future. The driving reason seems to be the poor braking with carbon wheels; adequate when dry and dangerous when wet (reported, I have not personally ridden carbon wheels in the rain). More R&D is planned using the new cyclocross rules; a sport where braking has never been considered paramount.


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## coachboyd (Jan 13, 2008)

I do think it's the way of the future especially for good braking in rainy conditions. I just had a chance to test out a road bike with disc brakes, with standard wheels and nothing too fancy the bike was 17 pounds so it's not really a huge weight penalty. One nice thing about them is it will change the standard size of the rear triangle to 135mm instead of the current 130mm (which could translate into stiffer wheels).

One thing to be aware of though it that for time trialing you won't want to use disc brakes. This means you would need separate wheels specifically for the time trial bike. . .no more swapping back and forth between road and TT (for both training and racing wheels)


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## tednugent (Apr 26, 2010)

disc brakes plus carbon wheels? sounds like an oxymoron to me

it's great on my 29er...hitting the technical trails...


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## TomH (Oct 6, 2008)

Disc brakes are great for mtb, where you really need to decelerate a bike with huge knobby tires as fast as possible, over and over. 

If you go for a full blast threshold brake jam on the road, you're going to cause a crash in any sort of road ride, even with caliper brakes. That, or you're locking up and skidding. Braking is ultimately limited by tire grip, and we dont have that much. 

I think its probably the "future" of road bikes, but its completely unnecessary. Even if free, id stick to what ive got now.


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## 88 rex (Mar 18, 2008)

TomH said:


> If you go for a full blast threshold brake jam on the road, you're going to cause a crash in any sort of road ride, even with caliper brakes. That, or you're locking up and skidding. Braking is ultimately limited by tire grip, and we dont have that much.


Have you ridden a road bike with disc brakes?


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## velodog (Sep 26, 2007)

Disc brakes for road bikes are an elegant solution for a non existent problem.


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## PlatyPius (Feb 1, 2009)

velodog said:


> Disc brakes for road bikes are an elegant solution for a non existent problem.


I wouldn't say that. When my fat ass gets flying down a hill and there's a stop at the bottom I didn't know about, brakes that really work would be nice. Dura Ace ain't good enough, even with salmon Kool Stop pads. Disc brakes are gooder. 

Looks-wise, I think disc brakes on a road bike are hideous.


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## zsir (Nov 14, 2008)

recently I was discussing this topic with a wheel builder. He doesn't like the idea. Said the added stress from a hub mounted disc and the weight added from the necessary hub upgrade plus the constant battle of trying to keep a wheel true while being lite enough for competitive road use .... well he was less than enthusiastic

Sent from my VTAB1008 using Tapatalk


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## iclypso (Jul 6, 2011)

Disc on front, rim brakes on rear? Then you don't need a whole new wheelset for TT, just a new front wheel. Plus, rear spacing stays at 130.


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## Dajianshan (Jul 15, 2007)

From what I have heard from various engineers at Taiwanese OEMs, hydraulic disc and rim brakes are the future of road bike braking. One manufacturer I talked to is deep in the development of a hydraulic disc braking system that is too sensitive for CX racing and optimized for the larger road market. I believe they are shopping the system around to the big guns who are willing to pay top dollar for the technology. 

Just what I have heard around the Taiwanese drinking fountain.


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## coachboyd (Jan 13, 2008)

iclypso said:


> Disc on front, rim brakes on rear? Then you don't need a whole new wheelset for TT, just a new front wheel. Plus, rear spacing stays at 130.


The front is where you wouldn't want the disc brakes in a time trial, they are definitely not aero, especially considering how many of the completely hidden front brake calipers are showing up on TT bikes.

I was just in Taiwan when I was on the road bike with disc brakes. It was a hydraulic disc brake system, there was no pulsating or grabby feeling.


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## iclypso (Jul 6, 2011)

^ Exactly. That's why you put the rim brake wheel on for TT. The disc brake wheel is for regular road riding.


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## Dream Plus (Feb 4, 2004)

I guess my question would be - does using disks allow better braking without "locking up" the wheel? Seems to me stoppping is limited by tire patch and grip more than brakes. I've been next to people who wore a hole in their tire in panic stops during races. I could see disk utility when you are braking without "locking up" like down mountains where your rims could heat up.



coachboyd said:


> The front is where you wouldn't want the disc brakes in a time trial, they are definitely not aero, especially considering how many of the completely hidden front brake calipers are showing up on TT bikes.
> 
> I was just in Taiwan when I was on the road bike with disc brakes. It was a hydraulic disc brake system, there was no pulsating or grabby feeling.


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## donttazmebro (Dec 26, 2007)

ive built a steel road bike with BB7's and have been commuting on it for the last year.

I have an Sworks roubaix with carbon roval wheels and swiss stop brakes and a ridley crossbow with trp brakes

my steel bike is hands down the best braking surest stopping bike i own. It's not about ultimate braking power because in the dry my roubiax can lock up that little tire going 10mph. it's about threshold braking. my disc roadie has a much higher threshold before lock up meaning i can grab later and harder without fear of either going over the bars or lowsiding.

disc brakes are superior in every way to rim brakes sans weight. I will gladly give up even 1lb on any of my bikes for the security of disc brake stopping power.

another thing is pad/disc wear.

when it rains here i could run through a set of rim brakes in a week. ive gone 1 year in the pacnw rain or shine and i still have plenty of life left on my disc rotors and pads. 

I am wearing out my rear hub faster than brakes.

any roadie that doesn't see the hype in discs for road i challenge you to ride a disc road bike for 200 miles then do the same route on your rim brake bike. you will see very clearly why so many of us are so excited for the future


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## tednugent (Apr 26, 2010)

you're buying carbon wheels for weight, right? then add back more weight for the rotor, 6 screws, probably a heavier caliper, more weight in lines & housing.....

doesn't make sense to me.

disc brakes are making their way into cyclocross bikes....


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## PlatyPius (Feb 1, 2009)

tednugent said:


> you're buying carbon wheels simply because everyone else has them even though they're often heavier, right?


Fixed that for you....


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## motobecane69 (Apr 8, 2011)

donttazmebro said:


> ive built a steel road bike with BB7's and have been commuting on it for the last year.
> 
> I have an Sworks roubaix with carbon roval wheels and swiss stop brakes and a ridley crossbow with trp brakes
> 
> ...


i agree completely. i put disc brake on the front of my commuter bike because i knew i'd be riding in rain and snow and assorted shitty weather. braking was great. that bike got stolen, now my new touring bike that i'm using for a commuter has a 1" fork and i'm not sold on getting a 1" carbon cx fork from nashbar to do the same thing. after riding in rain 3 days the past week, I'm gonna do it. the braking of my canti's absolutely sucks. I do realized that cantis brake worse than calipers but even on my other road bike, the braking in the wet is terrible. I don't care about the weight penalty because it's not going to add much rotational weight, the added weight is gonna be at the hub not on the perimeter of the wheel. 

with all of that said, I'm 240lbs so obviously, it's tougher to stop me at speed than a road racer. Putting disc brakes on will sell more bikes. it will make them seem like cars and people will buy into it. when is the last time you saw a car with drum brakes in the back? the industry went to 4 wheel disc brakes years ago, even though they weren't necessary.


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## mungoman58 (Aug 22, 2009)

*Forgetting something*

No one seems to have mentioned the other great benefit of disc brakes. That benefit being the the elimination of the risk of blowing a tire (melting the glue of a tubular or blowing the tube of a clincher) off the rim while descending due to excess heat build up from rim brakes (granted it takes quite a long decent for this to potentially happen). This can't happen with a disk set up. It will also mean potentially lighter rims as there will no longer be a need to have a lot of material specifically for the rim tracks. However, this weight may very well be added back in order to handle the increase in braking of a disk brake.


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## 88 rex (Mar 18, 2008)

tednugent said:


> you're buying carbon wheels for weight, right?


Strength AND weight


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## sp3000 (Jul 10, 2007)

I had a Cannondale hard tail MTB years ago, I had a set of Shimano XTR disc hubs built to Mavic Open Pro rims running GP4000 tyres. I rode that as my commuter bike, and MTB. I now ride a Dura-Ace road bike. 
The Shimano XTR disc brakes where 1000x better than my Dura-Ace (7800 with 7900 pads). The whole lock up argument based on grip is largely irrelevant, both will lock up just fine when you grab them hard, the real difference comes in normal use. With the XTR you can be going down the steepest hill and lightly modulate the brakes with one finger and have a very linear speed change, on the Dura-Ace you have to use more power and if you are coming to a stop from a fast steep down hill to say a T-intersection you really feel like your going to run out brakes, I end up in the drops pulling at the very bottom of the levers to get enough power, the discs do not have this issue they just keep stopping with minimal power. This power results in you pulling up earlier, being able to wash speed off going faster without really slamming them on and risking a lock-up.

Discs are better than rim brakes, no contest other than weight and I'm sure that will come down to make it negligible. And as for those that sight more maintenance, it all depends on the system, I have 2 MTB's one with Shimano XTR and the other with Formula Oro, the shimano are mineral oil, the formula DOT 4, the Shimano's are virtually maintenance free, one bleed every few years if I can be bothered, the Formula's can require some fiddling due to squeal but hey, they are Italian, what did I expect!

Bring on road discs I say, not to mention they work just as well in the wet.

I have one final disclaimer, I think caliper brakes look better on Road bike, but I'm a bit of a traditionalist! It will be interesting to see what new frame designs will look like.


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## TomH (Oct 6, 2008)

88 rex said:


> Have you ridden a road bike with disc brakes?


Yes, but the quote you did had to do with hard braking and braking power, not disc brakes.  You'd have similar problems jamming the brakes on normal calipers. 

For instance, ive never heard the term "hand pump" used in road cycling. Its a common term mountain biking, and good, strong disc brakes solved or *greatly* improved that issue. The majority of us arent doing near lock up braking over and over through our rides. 



> That benefit being the the elimination of the risk of blowing a tire (melting the glue of a tubular or blowing the tube of a clincher) off the rim while descending due to excess heat build up from rim brakes (granted it takes quite a long decent for this to potentially happen). This can't happen with a disk set up.


If you're braking that much, you're braking enough to overheat a rotor. Losing brakes at speed is pretty scary. Discs sure arent a cure for overheating!


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## 88 rex (Mar 18, 2008)

TomH said:


> Yes, but the quote you did had to do with hard braking and braking power, not disc brakes.  You'd have similar problems jamming the brakes on normal calipers.
> 
> For instance, ive never heard the term "hand pump" used in road cycling. Its a common term mountain biking, and good, strong disc brakes solved or *greatly* improved that issue. The majority of us arent doing near lock up braking over and over through our rides.
> 
> ...


If by jamming the brakes you mean locking them up when at the limits, then I would disagree. You are far more likely to be at your limits when braking while still maintaining control with discs. Over the last 3 years I've had a few "whoopsies" where I would come screaming down a hill only to encounter a stop sign. I was able to get HARD on the brakes without locking them up. On my caliper bikes, there were a few times I was hard on the brakes and they would suddenly lock up. Never crashed, but it is enough to scare you. Obviously in racing you are far less likely to be threshold braking.

Hand pump? Do explain. It's a pretty common term that apparently doesn't register on MTBR. I've never heard it used road or mountain. 

Overheating a rotor....... Rotors will get hot, but do you have any data to support you will lose your brakes. I've never lost my brakes due to heat road or mtb. Never rolled a tubie either due to heat on calipers. I have though encountered the glue get "tacky" from braking on calipers. Also, don't forget that when coming down hill the air does have a cooling effect on the rotors. 

I'm NOT saying disc brakes are the end all best thing in the world. However, it seems apparent that there is lots of speculation going on that has little basis for fact. I have ridden discs on my CX bike for 3 years now. That includes road rides, CX races, dirt road races, single track, commuting. I have put plenty of miles on my bike in all types of conditions and I can say that from experience, a lot of the speculating on this board is nonsense. All brakes brakes work, even a fixed gear can stop a bike, but some of these arguments against disc brakes are getting tiresome.


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## sp3000 (Jul 10, 2007)

88 rex said:


> but some of these arguments against disc brakes are getting tiresome.


I couldn't agree more, looks like the arguments come from blue blooded roadies that have never ridden a bike with (good) discs in their life.

To address disc brakes and heat, in MTB'ing you experience 2 things, one is a little brake fade after extreme downhill sections with very heavy braking with virtually no brake releasing, this can be minimised with technique, the second and what can happen after brake fade is you get heating of your brake fluid which causes the brake to pump up a bit at the master cylinder, this usually affects lever throw and can in extreme cases pump out the pads enough to rub the rotor. 

Either way, these effects are minimal and the brake systems are getting so good that one nearly never experiences these issues, however riding a caliper brake you always experience the lack of power, extra effort and lack of response under heavy braking.

But as I said before, calipers do look nice on road bikes! :thumbsup:


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## DIRT BOY (Aug 22, 2002)

Dajianshan said:


> From what I have heard from various engineers at Taiwanese OEMs, hydraulic disc and rim brakes are the future of road bike braking. One manufacturer I talked to is deep in the development of a hydraulic disc braking system that is too sensitive for CX racing and optimized for the larger road market. I believe they are shopping the system around to the big guns who are willing to pay top dollar for the technology.
> 
> Just what I have heard around the Taiwanese drinking fountain.


You are correct and its coming. People need to wake up and realize it. Braking on the best full carbon rims is not the best right now in dry conditions. Wet makes it even worse. Then carbon clinchers and tub heating issues. 

Canyon built a sub 6.8kg with dual 120mm rotors up front and a single 120mm rotor in back.











Canyon | Technology | Project Studies | Project 6.8

I look forward to the day we need this mid-level to high end rode bikes.


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## TomH (Oct 6, 2008)

88 rex said:


> Overheating a rotor....... Rotors will get hot, but do you have any data to support you will lose your brakes.


I dont know if i need data to prove that rubbing a metal pad against a metal rotor will heat it up. I kind of assumed thats something we all agree on. Brake fade is a common occurrence in mountain biking. Run of the mill kinda stuff. The cure is big rotors, I dont want to run 8 inch rotors on my road bike to stop them from smoking on long descents. 


> However, it seems apparent that there is lots of speculation going on that has little basis for fact.


it seems more that people are ignoring years of disc brakes being on mountain bikes. You not believing that discs overheat is a pretty glowing example of that! 

Hand pump is when you have weak brakes and your hand cramps from squeezing them to death. Road brakes are horrible in comparison to mountain bike brakes, but hand pump isnt even a term in the roadie world. We dont need to brake like mountain bikers. For the majority of us, its all about smooth, light braking to regulate speed, and an occasional hard brake to come to a stop. 

Disc brakes on mountain bikes cured hand pump and made it easy to apply tons of stopping power over and over. Getting really aggressive in the dirt with weak brakes, or v-brakes gets hairy. What are we trying to solve in road biking? Ive done some steep, looong descents on the road bike riding with slower people... I can drag the brake nearly the whole time to keep pace without worry. Ive smoked 6 inch discs in a 2 mile descent on the mountain bike (literally smoke coming off them). Its scary losing brakes. 

They have a wet weather advantage too, it makes sense for cross bikes, and even commuters/winter bikes. Racing bikes going 50mph with a lightweight disc brake system sounds like a disaster to me.


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## tednugent (Apr 26, 2010)

I haven't experienced brake fade yet on my BB5's with organic pads... but with the heat... I have had the AVID rotors warp on me, which is quite irritating.

With DOT 5.1 fluid... has anyone really experienced fluid fade?


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## willstylez (Sep 15, 2011)

My first set of disc brakes were Grimecas (roughly 10+ yrs ago), which used DOT fluid. Started out with them on my x-country bike with 6" rotors and there was little to no fluid fade. As I got into Downhill riding/racing, I switched them over wtih 8" rotors...and real sketchy, due to fluid fade. Had to pick and choose carefully where to brake, since by the time I would get to the end of a run, there would be zero lever left. Eventually I switched over to Avid Juicy 7's on my DH bike, again DOT fluid, which were flawless all the way around. So I basically think its the manufactuer/design of the system, not necessarily the fluid.

In regrads to disc brakes on a road bike, my first impression is that it's nonsense. But then again, i have never ridden a carbon rim. As a few other posters have said, why ride a carbon wheelset (to save weight) and then add that weight back on with a hydraulic brake system? Just roll with aluminum rims when the weather calls for it. Obviously, for cyclecross, it makes since since the conditions are similar to x-country mtbing.


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## 88 rex (Mar 18, 2008)

TomH said:


> I dont know if i need data to prove that rubbing a metal pad against a metal rotor will heat it up. I kind of assumed thats something we all agree on. Brake fade is a common occurrence in mountain biking. Run of the mill kinda stuff. The cure is big rotors, I dont want to run 8 inch rotors on my road bike to stop them from smoking on long descents.
> 
> it seems more that people are ignoring years of disc brakes being on mountain bikes. You not believing that discs overheat is a pretty glowing example of that!
> 
> ...


No point in kicking this horse too much more. Once you wrap your head around the difference between heat build up and over heating then maybe you'll get part of why you're wrong. You can't seriously compare throwing a 40lb rig down a moutain and expect a serious conversation about road bikes and braking. My MTB has 160mm up front and 140mm on the rear, as well as my CX bike. 

BTW, don't ride carbon bikes because they asplode in sunlight.


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## danl1 (Jul 23, 2005)

All the arguments in both directions are missing the point.

There's no such thing as one bike to rule them all. 

As a wet-weather commuting steed, discs are ideal.

As an all-out raceday bike, calipers will (usually) make more sense.

For newbs that lack the experience to use their calipers well, there are lots of hybrids with calipers.

More bikes for everyone! Quite arguing and enjoy the ride.


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## TomH (Oct 6, 2008)

88 rex said:


> Once you wrap your head around the difference between heat build up and over heating then maybe you'll get part of why you're wrong.


If you've got something to say about it, ill give it a listen. Im an engineering major, im sure ill understand what point you're trying to make. What am I wrong about? That rotors overheat? heat buildup leads to overheating. 


> You can't seriously compare throwing a 40lb rig down a moutain and expect a serious conversation about road bikes and braking. My MTB has 160mm up front and 140mm on the rear, as well as my CX bike.


Mines about 28lbs. Bike weight is irrelevant anyway, so sure, we can use a 40lb bike for an example as well. The only thing thats going to matter is total rider weight. 

Mine has a 203/160. The bike i setup for a very light friend on a 32lb bike used 160/160, to ride the same trails. 

We've got plenty of 180lbs+ riders on here. Those guys descending big hills on lightweight 160mm rotors isnt a good idea. 

Caliper brakes work on road bikes for everyone for all kinds of riding. Im saying disc brakes arent going to work for everyone, and in many cases would be much worse than calipers. Dangerous even.


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## 88 rex (Mar 18, 2008)

TomH said:


> Caliper brakes work on road bikes for everyone for all kinds of riding. Im saying disc brakes arent going to work for everyone, and in many cases would be much worse than calipers. Dangerous even.


:lol:


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## Urb (Jul 19, 2010)

TomH said:


> Caliper brakes work on road bikes for everyone for all kinds of riding. Im saying disc brakes arent going to work for everyone, and in many cases would be much worse than calipers. Dangerous even.


Much worse and dangerous? Care to explain?

We all understand that motorcycles use disk brakes. Even crappy single disks on very heavy motorcyles have been reliable.


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## TomH (Oct 6, 2008)

I did above, losing brakes at speed is scary. I doubt we're going to see big brakes on road bikes. Its going to be a race for low weight. 

Cars use disc brakes too. Big, heavy, disc brakes. Bicycles are using 2mm thick rotors and calipers that dont pull much heat off. Cars and motorcycles experience fade and fluid boiling too, they just take a lot more heat input before. Brake fade and fluid boiling is a common concern in motorsports too. Anyone whos spent some time at the track probably has a story about the first time their pedal went straight to the floor after hot laps.

Cars and bikes are a pretty good example of what im saying. Road going commuter cars are extremely unlikely to ever boil their fluid, or feel brake fade. Put a truck on a big hill and its a concern ("save your brakes trucker signs, etc), or put those same cars on a high speed track and all of a sudden its a big concern.

What works for commuting and winter bikes is going to be scary on competition stuff. Rim brakes dont have much power, but they've got a huge "rotor" that dissipates heat pretty well.

Weve already seen carbon rim delamination and tubular glue coming undone on whats essentially 700mm rotors. were going to switch to 160mm rotors, the same rules are going to apply for heat.


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## tednugent (Apr 26, 2010)

TomH said:


> If you've got something to say about it, ill give it a listen. Im an engineering major, im sure ill understand what point you're trying to make. What am I wrong about? That rotors overheat? heat buildup leads to overheating.
> 
> Mines about 28lbs. Bike weight is irrelevant anyway, so sure, we can use a 40lb bike for an example as well. The only thing thats going to matter is total rider weight.
> 
> ...


your an engineering major.... big whoop. are we supposed to take what you say as fact?

I do just fine on my 29-er descending steep, technical sections with Avid BB5 and Alligator I-wave 160mm rotors (front and rear)

when kids say they are an engineer or studying engineering in undergrad.... it is a sign that they are desperate for credibility


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## Urb (Jul 19, 2010)

TomH said:


> I did above, losing brakes at speed is scary. I doubt we're going to see big brakes on road bikes. Its going to be a race for low weight.
> 
> Cars use disc brakes too. Big, heavy, disc brakes. Bicycles are using 2mm thick rotors and calipers that dont pull much heat off. Cars and motorcycles experience fade and fluid boiling too, they just take a lot more heat input before. Brake fade and fluid boiling is a common concern in motorsports too. Anyone whos spent some time at the track probably has a story about the first time their pedal went straight to the floor after hot laps.
> 
> ...



We are talking thresholds here. I haven't seen or read any issue with disk brakes experiencing brake fad whatsoever. If anything current disk brake design offers more stopping power than is required. Most disk brakes on bicycles work with a cable so how would brake fad occur? I've never heard of a bicycle disk break warping due to heat. Impact sure but not heat.

Do you have examples of disk brake failure on bicycles that warrent your concern?


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## TomH (Oct 6, 2008)

tednugent said:


> your an engineering major.... big whoop. are we supposed to take what you say as fact?
> 
> I do just fine on my 29-er descending steep, technical sections with Avid BB5 and Alligator I-wave 160mm rotors (front and rear)
> 
> when kids say they are an engineer or studying engineering in undergrad.... it is a sign that they are desperate for credibility


he was asking for data and claimed im not understanding. if he wants to get technical and throw up data, im saying im going to understand it. i didnt say "look at me, im an engineer!". But good cheap shot. 



> I haven't seen or read any issue with disk brakes experiencing brake fad whatsoever.


http://forums.mtbr.com/brake-time/brake-fade-675439.html
http://forums.mtbr.com/downhill-freeride/brake-fade-braking-technique-640979.html
http://forums.mtbr.com/brake-time/questionaire-brake-fade-495150.html
http://forums.mtbr.com/trek/remedy-9-brake-fade-483377.html
http://forums.mtbr.com/brake-time/juicy-5-brake-fade-303393.html

Theres actually 23 pages that turn up in search for "brake fade". Discs warp commonly enough, park even makes a tool to readjust them. Its not really an issue since its so easy to fix. 


> Do you have examples of disk brake failure on bicycles that warrent your concern?


Having overheated and faded a bunch of 160mm rotors personally, yes. Its scary, and not fun.


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## TomH (Oct 6, 2008)

double post.

Im almost baffled that people are willing to argue that brake fade exists with disc brakes. Its undeniable, well documented, with who knows how many thousands of people having experienced it. 

If you have 160mm rotors and go screaming down a mountain with disc brakes, good luck. They have their place, they even have their place on road bikes. Its crazy to think they belong on everything road related, especially with the industries push towards lightweight everything.


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## kanekikapu (Jan 23, 2002)

Honestly I don't mind having disc brakes on carbon hoops if it can give me more power and modulation. Always down for more of those.


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## ziscwg (Apr 19, 2010)

velodog said:


> Disc brakes for road bikes are an elegant solution for a non existent problem.


I guess that depends on where you live, ride, and how you ride. I'm to say in Florida, not needed. In CO, or CA, ummmmmmmmmmmmm yeah, they would be nice.

Having some nice lite carbon wheels to get up the mtn, but then not having to worry about the braking on the way down.


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## penn_rider (Jul 11, 2009)

Tom is pretty much correct. However, some of the problems that our MTB counterparts experience can be attributed to poor design or a bad batch of metal. Brake fade is an issue, but I have yet to have mine get poor enough not to stop or fail altogether. 

Essentially, all of the brake complaints floating over on MTBR will be echoed here when the time comes.


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## 88 rex (Mar 18, 2008)

TomH said:


> Anyone whos spent some time at the track probably has a story about the first time their pedal went straight to the floor after hot laps.




Have you spent time at a track? Stock pads and fluid? I have spent time and I set my car up appropriately and I didn't boil my fluid. Boiling your brakes does happen, but it's a whole different bowl of wax compared to bikes. Brakes run better when hot, just not overheating hot. 

"Warped" rotors is a generic term that is not an actual occurance so folks who complain about "warped" rotors aren't really warping their rotors due to heat. 

Lets also not forget that anyone with drop bars is currently running a cable and not fluid.


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## donttazmebro (Dec 26, 2007)

I think that brake fade in MTB is extremely different than what a roadie will see

Ive done downhill riding at whistler mtb park with a hydro disc bike. I am on the brakes hard in some sections almost stopping and wide open in others.

Ive also descended the roads of mt rainier (20 miles down hill switch back) on my full carbon roadie never doing any kind of braking similar to the true downhill riding of Whistler.

You won't be more apt to fade disc brakes than rim brakes. Hydro or Mech. I am 20x more confident descending on my disc brake bike than my rim brake bikes.

Disc brakes, for shear braking power (not counting looks and weight) will easily out brake any rim brake bike on 50mph descents in rain or shine and twice on sundays.

Will a disc brake wheel weigh as little as a rim brake will? Sure but not today. there aren't hoops being built in narrow road form specifically for disc brakes.

If i build a 1300gr wheelset for my disc brakes on average im adding an additiional ~150gr total front and rear to the Wheel (Alligator Aries rotors).

Im also adding more weight to the bike because of the calipers, but i'll just leave my saddle bag off and we'll call it even


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## tednugent (Apr 26, 2010)

88 rex said:


> Have you spent time at a track? Stock pads and fluid? I have spent time and I set my car up appropriately and I didn't boil my fluid. Boiling your brakes does happen, but it's a whole different bowl of wax compared to bikes. Brakes run better when hot, just not overheating hot.
> 
> "Warped" rotors is a generic term that is not an actual occurance so folks who complain about "warped" rotors aren't really warping their rotors due to heat.
> 
> Lets also not forget that anyone with drop bars is currently running a cable and not fluid.


I've experienced pad fade.... that's a little scary going into a tight curve with stock rotors and pads....

bicycles is a different story from cars though.....

stainless steel is a poor choice material to begin with, that's why cars still use cast iron alloy or ceramic (for the really expensive high performance cars).....

gong with a larger bicycle rotor is not the cure for fade.... the weight difference doesn't make much of a difference.... it's something called "leverage" which rim brakes actually have more of

bicycle rotors are vented anyway, so if the pads do outgas, there is a place for it to go, which minimizes pad fade

fluid? petroleum based fluid is extremely hydroscopic.... so lack of maintenance will lower the boiling point.... even worse is buying a big can and not using it in a timely fashion. my car doesn't take a full liter of brake fluid.... bicycles take a lot less. so every time you open the bottle to use, it absorbs more moisture.... buying smaller bottles is better for bicycles

yes, rotor warp in cars is actually a myth.... a free body diagram won't explain it too well.... it is more materials science


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## 88 rex (Mar 18, 2008)

tednugent said:


> fluid? petroleum based fluid is extremely hydroscopic.... so lack of maintenance will lower the boiling point.... even worse is buying a big can and not using it in a timely fashion. my car doesn't take a full liter of brake fluid.... bicycles take a lot less. so every time you open the bottle to use, it absorbs more moisture.... buying smaller bottles is better for bicycles



For the track car (which is sadly sold now) I never used open cans. It was an absolute no no. On the family car, maybe, depends. Kind of makes people give you a funny look when you tell the fluid is anhydrous and should be tossed after you've opened it. MTB's take so little fluid that even the smallest bottles are overkill.


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## tednugent (Apr 26, 2010)

88 rex said:


> For the track car (which is sadly sold now) I never used open cans. It was an absolute no no. On the family car, maybe, depends. Kind of makes people give you a funny look when you tell the fluid is anhydrous and should be tossed after you've opened it. MTB's take so little fluid that even the smallest bottles are overkill.


most people don't change their brake fluid in their cars to begin with.... I do mine every 2 years, though with a low-viscosity DOT4 due to the ESP system


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## ziscwg (Apr 19, 2010)

penn_rider said:


> Tom is pretty much correct. However, some of the problems that our MTB counterparts experience can be attributed to poor design or a bad batch of metal. Brake fade is an issue, but I have yet to have mine get poor enough not to stop or fail altogether.
> 
> Essentially, all of the brake complaints floating over on MTBR will be echoed here when the time comes.


I agree that I have never had my mtb discs fail when they get over heated. They don't have quite the feel I love, but still work. Some of my mtb overheats were from poor braking habits on the dirt.


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## ziscwg (Apr 19, 2010)

88 rex said:


> For the track car (which is sadly sold now) I never used open cans. It was an absolute no no. On the family car, maybe, depends. Kind of makes people give you a funny look when you tell the fluid is anhydrous and should be tossed after you've opened it. MTB's take so little fluid that even the smallest bottles are overkill.


One thing that helps this is an old trick from the photography world before digital. You get air out of the bottle. I photography, we used collapsible bottles.

For brake fluid, I fill the open bottle of brake fluid with glass marbles to get the fluid to the top.

It's not perfect, but it does reduce the moisture absorption problem.


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