Disc brakes

[Josh]

I thought this would be a good post from my blog to re-purpose for our forums, talk amongst yerselves:

I'll admit I have a fondness for disc brakes. I came to cyclocross from a mountain bike background. I haven't run rim brakes on any of my mountain bikes since 2000. I am happy to see them going the way of the Dodo.

Here's an interesting story from Velo News to peruse, Next big thing: disc brakes on road bikes.

Cyclocross is a different story.

Banned from cross? Well kinda. Depends on who you are and the sanctioning body under which you race.

Discussions of the pros and cons of disc brakes generally ignite heated debates among members of the cyclocross community

Many of the reasons given for not using disc brakes — weight penalty, overkill for road and cyclocross racing — have less to do with using disc brakes than using brakes designed for mountain bikes.

There's no way around it, discs will always weigh more than canti's. But they don't have to weigh as much as they do now. When it comes to using disc brakes with road levers there's very little selection. Last time I checked the number of mechanical disc brakes designed for use with road levers was two: the road version of the venerable Avid BB-7 and Tektro's Lyra.

Per wheel the road BB-7's weigh in at 361 grams. The Lyra has a published weight of 148 grams per wheel. These weights include caliper, rotor and mounting hardware.

The Lyra is sign of things to come; 140mm rotors instead of the traditional 160mm sizing reduce weight as well as stopping power. The reduction in braking power is not necessarily a bad thing. Disc brakes with equipped with 140mm rotors can provide more stopping power than cantilever brakes while decreasing the weight penalty.

There's a lot more that has to happen than designing road and 'cross-specific disc brakes. Frames, forks and rims all have to be strengthened. Even though it may be small, there's a weight penalty incurred in a disc-specific road or cross bike frameset and wheelset.

There are significant benefits. Disc brakes outshine rim brakes when conditions turn nasty. Mud, water, sand and ice wreak havoc on rims and brake pads while decreasing braking performance. Discs are less effected by adverse conditions. Wheel changes can be faster with discs, flip the quick release, pull the wheel out — no fussing with the brakes.

If I were to make a prediction, it would be that as commuter bikes become more prevalent, so too will disc brakes for road and cross. I don't think Sven Nys or Tim Johnson will be straddling disc-equipped race bikes anytime soon, but for the the weekend warrior — for whom a cyclocross bike is a commuter / utility bike first and a race bike second — discs make perfect sense.

[andrew]

i'm curious as to what the #1 reason for a pro rider pitting in a race, beyond mechanical problems (flats, something breaks). is it mud messing up shifting, or clearance issues, or just overall dirt/weight issues in sloppy conditions? this might give more color on how much benefit this might have for top riders in sloppy conditions. Maybe we can get Christine, Mark to contribute their expert opinions.

[Kiwimark]

Aside from having to change all of the frames and forks over to Disc brake compatibility the other issue is changing some expensive wheels or hubs (lots of wheel rebuilds) over to a mechanical disc. Mechanical disc brakes have very little modulation in their action which is a very strong reason why you don't see them on any pro mountain bike setups or off the rack highend mtb's.
The other issue is brake power. Cyclocross racing doesn't have the high speed hard braking sections you have in MTB racing. The longest descent in a cyclocross race could be 20-30secs at most compared to MTB racing which if you race around here in Colorado it could be 20mins. The longest braking time of maximal force is generally 10secs in the majority of races. That doesn't mean you won't be dropping down a long hill on the brakes but the maximal force you use is a very short time period.
As for the UCI and riding disc brakes during training they are concerned with riders on disc brakes training on the World Cup races or other large UCI races.
Disc brakes are not going to happen with the UCI the market force or the ground level cyclocross market. I think I saw two bikes with disc brakes at the races last season (don't reply telling me you saw three guys in your category last year because three guys aren't going to keep the local store in business... provocative eh!)
So what's really the next big thing in cyclocross??
Sram chains that don't break?
Mike Kluge finally changes his name to Hasselhoff...

[Christine "Peanut" Vardaros]

I am a former mtb racer so i have no problems with disc brakes because they are from the mtb world. But with some mtb disc brake setups i've seen, you have to put the wheel in perfectly straight otherwise the disc will hit the brake pad.
Other than the fact that it is illegal to enter a uci race with disc brakes, I am a bit hesitant about their strength - they are just too strong. With cantilevers it is very difficult to lock up the brake. This is good thing for my riding for safety sake as well as for effectiveness since i can't really slow the bike down too much, making my re-acceleration not as exhausting.
I am a little less decided on top mount lever brakes, though...

[Christine "Peanut" Vardaros]

Hi andrew:
We come into the pits sometimes for flat tires or mechanicals, but mostly for the mud. It can add an exorbitant amount of weight to the bike, but even more troublesome is when it interferes with tire clearance, shifting and the ability to clip into the pedals. I use speedplay frogs so i usually can get into my pedals simply with a smack to the pedals with my foot - at most. Sometimes we'll realize we have the wrong tire pressure or even the wrong tires for the terrain since often times the course will change due to rain or the earlier 'category races' changing the terrain. After riding by the pit and yelling our needs, on the next round we will come into the pit to get the more appropriate tire/pressure setup.
For the select FEW, they may change bikes on the last lap just before the finish to show off a clean bike as they zoom in for the win. Or sometimes the riders will grab their bike with slicks on if they think it will come to a sprint finish (a rare occurrence, though.)
Hope this helps!
A bit more than 4 LONG months left until playtime!

[andrew]

That makes sense - general mud issues as opposed to one specific mud problem (clearance, shifting, pedals, weight). Disc brakes therefore would only potentially solve the clearance issue.

Speedplay frogs huh? Interesting. What do you like about them? Anyone else in the pros using them? Pedals are so personal...

[Surly Bastard]

Any issue with safety? Those things look like pizza-slicers to me. And a shouldered bike on a crowded first lap run-up? Hey it's not like I never got a wheel in my chops before. If the UCI does legalize discs they'll probably mandate retractable guards like power saws so the set up will weigh like 15 pounds.

I'm not old school, but I just can't see discs for cross. Great on a mtb, but not my cross bike. (Or how about hydraulic brakes on a road bike in a crit? Wouldn't that be fun?) But I do agree the commuter market could really benefit.

Maintaining a ban on discs also gives the UCI something to do. Given more free time who knows ? Just be thankful we don't HAVE to use downtube shifters ... not that there's anything wrong with that ...

[jeremyb]

i saw a custom de salvo at a cross crusade race that had a disc front and canti rear.

If i was to put together another cross bike, id put a disc fork on it and do the same. Makes sense in that the front brake does a large majority of the braking.

Boosts the weight, but you get extreme braking power.