Zinn: disc brakes on road bikes next big thing

[Sylv]

From Velonews:

[quote]Now, on to gear. Here it is: a Next Big Thing will be disc brakes for road bikes. The first thing that comes to mind when writing this is that Ed "Scotty" Scott, the originator of the red Scott/Mathauser brake pads and Scott brakes would roll over in his grave if he heard me predicting something like that. Scotty told me decades ago that disc brakes on bikes were stupid, given that there already was a perfectly good braking surface already on a bike, namely the rim. However, though their demands are far different, nobody would ever make that argument regarding a motorcycle or a car, and drivers of those vehicles do not expect to lose their brakes in the rain or after going through a big puddle, as bike riders with rim brakes must, nor do they expect grabbiness or fade on a hot day.

Of course, the real reason to even consider disc brakes is improved braking. And the fact that so many mountain bike cross-country racers use discs despite the weight penalty, even on dry courses, indicates that better braking can actually make you ride faster.

Road disc brakes periodically make a brief splash at a bike show, but they always disappear again because of their Achilles heel, namely that they are considerably heavier than current road brakes. And it is not just the weight of the brake itself; keep in mind that the fork would need to be beefed up at the ends and have integrated mounts, the hubs would have to have a rotor-mounting flange, and the spokes would need to be more numerous and laced in a crossing pattern to counteract the torque on the hub. On the other hand, the rims could be lighter if they did not have a brake track, and tires could conceivably be a bit lighter as well, if they did not have to deal with as much heat buildup. Less weight out at the edges of the wheel translates into faster acceleration, which everyone other than a time trialist or triathlete on a straight course can appreciate.

There is one other weight-related problem road discs must overcome; given the weight constraints that road disc brakes will have to meet, the rotors will be very small. Small rotors and high speeds means that heat buildup will be an issue.

Technology may still be able to deal with these issues, and given the rapid development of composites used on bikes, it is not had to imagine that it could be soon. Argued to be only one-third the weight of their steel counterparts, carbon-on-carbon brakes saved 600kg off of the weight of the Concorde supersonic jetliner, and that was developed decades ago. Carbon-on-carbon brakes are standard in race cars. I don’t know how these would work at bike speeds, but in race cars, they are claimed to not fade under heavy usage like steel brakes.

There is room with the UCI weight limit to allow for somewhat heavier brakes and still meet the 6.8kg barrier teams would insist on in order to use them. Better braking and lighter rims might be good enough reasons for them to adopt them if the weight came down enough on the whole system. But then you have to worry about inciting a ban by the UCI, given that Eddy Merckx and Fausto Coppi never used them.

The UCI, slapping Cannondale’s hand, already banned disc brakes for cyclocross, stating that it was a performance advantage. That advantage is quite obvious to anybody who has compared the two on a muddy course. However, given the lower speeds and softer surfaces to land on, you don’t often see career-ending injuries from crashes in cyclocross, which you do in road racing, so there is not a counterbalancing safety argument to be made there.

However, with the proliferation of superlight carbon rims, there is a strong safety argument to be made on the road, and I actually think the UCI would be open to it. Nobody likes to see the kind of career-altering crash that eliminated Joseba Beloki from the 2003
Tour de France.

I am convinced that it would not have happened, had he been using disc brakes. The day was hot, the road surface was soft and melting, his brakes grabbed on his carbon rim and locked it up, causing it to skip sideways and tear the tire off of the rim when it hit. Disc brakes do not tend to grab in conditions like that.

I think that it is important how it is presented to the UCI whether road disc brakes will be rejected out of hand or not. As I said, I think that the UCI is open to safety arguments; it used that as justification for requirements for the use of hard-shell helmets and for the banning of Cinelli’s Spinaci clip-on handlebars. But if some upstart guy starts winning races on homemade disc brakes (remember the UCI’s cool reception of Graeme Obree’s innovations?) or on those of some small manufacturer, the prospects for getting it past the UCI do not look good.

Sadly, once the UCI has said “no” to something, it is hard to reverse that decision. However, if a big company in good standing with the UCI – a Shimano, Campagnolo, or SRAM, for example – were to make a nuanced argument to its rules committee ahead of time, before riders appeared in races with them, there might be a different outcome.

And contrary to what some may think, the UCI has not already closed the disc-brake door. In the UCI Cycling Regulations, this is the rule on that subject:

1.3.025 - Freewheels, multiple gears and brakes are not permitted for use on the track during competition or training.

Disc brakes are forbidden in cyclo-cross training and competition.

(text modified on 1.09.04; 1.01.05).


Disc brake makers have already been around the block a time or two with road bike product managers and have not gained a foothold yet. The Avid
BB7 mechanical road disc brake is still in SRAM’s line, but I’ll bet you’ve never heard of it.

No one has really invested the resources to solve the weight problems that must be overcome to get them on road racing bikes. Nonetheless, I think somebody will; I do foresee a future for road disc brakes.

[Elliot M]

[quote]Road disc brakes periodically make a brief splash at a bike show, but they always disappear again because of their Achilles heel, namely that they are considerably heavier than current road brakes. And it is not just the weight of the brake itself; keep in mind that the fork would need to be beefed up at the ends and have integrated mounts, the hubs would have to have a rotor-mounting flange, and the spokes would need to be more numerous and laced in a crossing pattern to counteract the torque on the hub

[Sylv]

Good find

Shimano will have a few years advance in technology compared to Campag!

[Daniel Gee]

Recenty I saw a review of an Orbea road frame/forks specifically designed for disc breaks-can't seem to find it anywhere but I'm certain I didn't imagine it

[-Adam-]

[quote="Sylv"]Good find

Shimano will have a few years advance in technology compared to Campag!

[Daniel Gee]

found it-not mad after all

[url]http://www.bikeradar.com/gear/category/bikes/road/product/diem-drop-disc-08-28049[/url]

[mrP(Boonen)VT]

Interesting concepts.

One of the snags is that if they are adopted in road racing, don't ride close behind if you have "normal" brakes - there were numerous crashes when dual pivots came out and stopped some riders quicker than others

[Ivor]

[quote]But then you have to worry about inciting a ban by the UCI, given that Eddy Merckx and Fausto Coppi never used them.