Road Cycling - why are disk breaks not popluar on road bikes??

Why aren't there more road bikes with disk brakes and why are they not legal under UCI??

two reasons: Weight and function. Disc brakes are heavier than rims, and they are not needed for the application on a road bike. There are a few road/urban bikes with them(Cannondale Bad Boy), but for the true road race bike, they are not at all needed, and would provide little benefit for the road bike, as most roadies savor every ounce and do not need to have tremendous stopping power that the disc brakes provide

Yeah, seirously. Good modern dual pivot brakes are very strong. I can lock up my back wheel if i just grab my brake lever hard enough. The only times i wish i had stronger brakes are when i'm descending down 20 percent grades. But then again, they wouldn't do that much if they just locked up wheel and skidded.

The only times i wish i had stronger brakes are when i'm descending down 20 percent grades. But then again, they wouldn't do that much if they just locked up wheel and skidded.

I know what you mean...

At least we work out our arm muscles and grip, once in a while..:D

I'd prefer my ATB's Avid discs on my road bike for those mountain rides. But, I don't want to pay the weight penalty as others have mentioned. I would want them for heavy touring. Airborne has a titanium light tourer/cycle-cross frame that you can spec with Avid discs. I'm seriously considering the frame, but I'm going to stay with rim brakes for the weight.

Al

Where discs might be beneficial is on long steep descents...like multiple mile ones. Rim brakes can overheat the rim over time, which can lead to flats...which at high speed can be ugly, on or off-road.

I don't do much road riding, especially in mountains, but i would imagine you would want to cut loose anyway and work for a high speed until you get to a turn, in which you use the brakes hard, but not before, is this the case? I think they would be more beneficial in tight urban riding to avoid the inevitable "door job"

Cyclocross, YES!

Road, NO!

Too much weight, not enough benefit!

L8R

Also, carbon road forks are not engineered to take the force applied by disk brakes. The force a disk brake applies on a fork is much closer to the hub. With a conventional dual pivot set up the force is applied at the crown where the fork is much beefier. I imagine if you wanted to make a carbon fork to work with disk brakes there would be a real weight penalty to beef up the fork legs to accomodate the extra forces being generated by the disk set-up.

I don't do much road riding, especially in mountains, but i would imagine you would want to cut loose anyway and work for a high speed until you get to a turn, in which you use the brakes hard, but not before, is this the case? I think they would be more beneficial in tight urban riding to avoid the inevitable "door job"

On extremely long, steep, descents (11+ miles in North Carolina, for example), you can just build up too much speed to safely navigate the twisty, gravelly, sometimes busy, two lane highways. In situations like that, it is trade off amongst hand fatigue, rim heat, and bleeding off speed. At least with clinchers, heat is less of an issue than with sewups.

Paul

Weight is the sole issue. Braking performance is much better with discs, as there is no fade - more power - less arm pump – better in the rain - etc. If you bend your rim, you can still ride and brake effectively. Moreover, disc pads last WAY longer than rim brakes.

Therefore, unless you are racing, IMHO, discs would be a better choice in pragmatic terms. However, from the manufacturer’s standpoint, there is pressure to get the weight low, and market all bikes as light racing bikes. So, don’t look for many choices in brakes anytime soon!

Therefore, unless you are racing, IMHO, discs would be a better choice in pragmatic terms. However, from the manufacturer’s standpoint, there is pressure to get the weight low, and market all bikes as light racing bikes. So, don’t look for many choices in brakes anytime soon!

I doubt that many cycle for pragmatic reasons. I ride for fun and the more my wife and I lighten our bikes, the more fun they are to ride. There's a well designed interactive model on the WEB for calculating the affects of weight and drag on speed or power requirements. I posted the hyperlink a while back. At my estimated power level, a 5 lb reduction in weight had a 7% speed benefit on a not too steep a grade.

I've lost 20 lbs body weight, and when I upgrade to a new bike this fall, that might get rid of another 10.

By the way, not all light bikes are racing bikes.

The problem with discs is it's not just the weight of the brake, but you likely have to use a mountain bike hub with that heavy flange. Those hubs are less aerodynamic too. That would not affect me as I ride under 20, but it would at the higher speeds that many ride.

Al

The caliper presses the pads to the disc, isn't this just what our "traditional" brakes are doing? It's just a big disc, certainly not a "drum"!

I doubt that many cycle for pragmatic reasons.

You misunderstood my comment. The thought I am trying to convey is that it's more practical to use disc brakes vs. rim brakes given the reasons I stated in my post. They are simply better @ stopping you, and if you're not counting grams, that's what matters most.

The caliper presses the pads to the disc, isn't this just what our "traditional" brakes are doing? It's just a big disc, certainly not a "drum"!

If you notice on discs, the contact surface area is much, much greater. Not to mention, the disc does not touch the tire like the rim does, therefore it can't melt the tire. I think discs would look cool on a road bike, and im sure that it is on the horizon to become mainstream and eventually we'll see lance haulin down his ass with a set of Hayes Hydros, but right now i think manufactures need to figure out how to "carbonize" the system. ;)

Good answers all except for one question. Why are they illegal under UCI rules?

becuase the UCI is trying to keep road bikeing tradional. that is why road bikes still have the double-triangle frame, they riders are drinking out of water bottles, and there are no bikes under 15 pounds. I can sorta see their point, without technological restrictions, I think racers would go nuts, and start to look like traithaletes...heh. I think it might be cool if riders were issued bikes that were exactly the same except for sizing...it would cut out the whole "equipment" issue that the uci deals with.

on the matter of discs, there is no point. they are too powerful, methinks. I can lock up my front wheel on my road bike, and thats about as powerful as I would want a brake to be. There is not enough rubber to harness the sheer braking force of a disc brake. remember, roadies are usually running rubber that is less then an inch wide. DHers and the like have tires that are 2.5'' and bigger to harness that braking force.

They should do an unlimited class of bicycle racing just to see what crazy things these manufacturers come up with! I think that they would try to defy gravity and fill frames with helium just to save three grams!

Aesthetically, I believe that rim brakes are much cooler than disc brakes. Road bikes are sleek creatures, definitely not when disc brakes are installed, it removes all the 'coolness' that surrounds a road bike.

Aesthetically, I believe that rim brakes are much cooler than disc brakes. Road bikes are sleek creatures, definitely not when disc brakes are installed, it removes all the 'coolness' that surrounds a road bike.


truer words were never spoken....thanks to all who responded

if you can lock up the front wheel and/or lift the rear, you probably don't need any more braking power.

and when caliper brakes weigh about 500g less than discs, there's no real point. the only issue might be the long descents thing, or ease/lack of maintainence on discs...

fsnl
sparky

From what Ive read front forks are not built for the torque in extreme situations.Like ewitz said a few posts up.It might work on the rear.

You can get some touring forks, built for disks, even carbon fibre ones. They are faily massive. I wonder if the extra stiffness has a negative effect on comfort. Most disks are used on sus forks, where stiffness does not affect the ride.

I'm surprised that the issue of locking up your wheels under even medium braking has taken so long to come up. While disc brakes have gotten better in terms of modulation, I'd imagine that it's still a lot easier to lock up a wheel or two with discs on a roadie bike than it is with calipers. And that's not something you want to deal with on any stretch of road. I think when folks talk of having more brake power than you need, they're basically saying that more brakes can actually result in less control, at least in this application.

I just thought of another thing...wouldn't the hunched over the front position of a road bike lead to more endos with discs? also, the added stress to already thin spokes...

I think dual pivot calipers on road bikes have much better modulation for light braking. Disks are "on" or "off", like air brakes on trucks.