Question born out of total ignorance: why is there a UCI ban on disc brakes for cross bikes? I would imagine that they would be rather useful...
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RDV4ROUBAIX said:Yes, the UCI rule is for safety reasons, which I don't agree with either, but a disk set-up for CX bikes doesn't make sense anyway. They're much heavier than a regular canti set-up, and you don't need that much stopping power to slow down a 17lbs carbon cross bike. I don't recall ever in a race where my cantis were not performing like they should in the worst wet, snow, rain, ice, mud. Disk is just plaine and simple overkill IMHO, not only is a disk brake set up heavier, the frames are too since you have to add more material to anchor it on the frame. Hubs are heavier as well.
dsut4392 said:All true, but in the MTB world we all went through the same thoughts - "who could _ever_ need more power than cantis", then "who could ever need more power than v-brakes", now it's "why in hell would you use anything other than a disc brake?"
The three main advantages I see are:
- consistency of performance in the worst conditions (mud, rain). It's not all about power, having a predictable response is worth a lot in terms of letting you get maximum braking without the tire losing traction and sliding out.
- ability to keep riding with a rim clogged up with mud or out of true (e.g. broken spoke), when cantis would mean totally disconnecting the brake to get enough clearance (if that is even enough).
- no wear on the rims, so your light, expensive wheels last much longer.
As far as the weight difference, an extra 200 gram at the hub is negligible - less than 0.3% of 68kg rider + 6.8kg bike, even less for big guys riding bikes that weigh more than 6.8kg.
icefire said:UCI just changed the rules for next season:
http://www.cyclingnews.com/news/uci-to-allow-disc-brakes-in-cyclo-cross-competition
We'll see how it goes
RDV4ROUBAIX said:..... and to top it all off, I just ordered my new CX F&F without disk brake mounts, even had the option to. Oh well, just have to get another. Had to rethink this one, and I really believe that D-brakes are going to take over cycling. It'll eventually be accepted for pro road too, just a matter of time before the systems get lighter, more compact, and consequently safer for the UCI to change their minds. Heck, if racers are willing to ride with the extra weight of a PT hub today, why not d-brake system.
RDV4ROUBAIX said:..... and to top it all off, I just ordered my new CX F&F without disk brake mounts, even had the option to. Oh well, just have to get another. Had to rethink this one, and I really believe that D-brakes are going to take over cycling. It'll eventually be accepted for pro road too, just a matter of time before the systems get lighter, more compact, and consequently safer for the UCI to change their minds. Heck, if racers are willing to ride with the extra weight of a PT hub today, why not d-brake system.
RDV4ROUBAIX said:most, if not all would stay with cantis just because of the huge weight difference. It's not just the hub that's heavier, it's the whole system, brakes, rotor, hubs, and frame, which comes to roughly 700g per wheel. That adds about 3 lbs to the total weight of the bike, not that big of a deal for the average rider, but the nature of CX racing, am or pro, that is totally unreasonable.
Yes seemingly without consultation but the UCI had a CX committee that did and these changes are from their recommendations.avanti said:Max tire width now 33 mm. Do my 35 mm Conti Cyclocross Speed tires meet the requirement? I just measured them and they are 33 mm wide so I hope officials don't rely on the manufacturer's stated size.
How is it that the UCI seemingly changes rules without input from the cycling community?
benlondon said:After a couple of years of development there won't be a weight penalty for disk brakes at all. Rims will be made lighter (as they don't need a braking surface)
JA.Tri said:Sorry for the detour .
Why are cantis currently used in CX rather than V brakes??
Ta js
durianrider said:Avid BB7's are the ticket. Easy to adjust on the fly, just as powerful as hydro's.
DirtyWorks said:Nice try, but no way.
Frame/Fork: think about the forces on the very end of the fork (a lever!) with a disc brake. Your fork weight will go way up. If it doesn't, then I'll pass on that fork. Same thing with the rear triangle.
DirtyWorks said:Wheels: gain lots of hub weight. Now, I'll give you that the rotational weight drops, but it is replaced by a much heavier hub and disc. The whole brake track argument is almost null because they are running sew-ups.
DirtyWorks said:Will there be rare occasions where discs provide some advantage? Yes. Will bike manufacturers shout from the rooftops that canti's are dead? Yes. Are they actually dead? No.
dsut4392 said:That argument is specious. The total energy dissipation is the same, so while you need to reinforce different areas with a disk brake compared to cantis, the total frame/fork weight need not differ significantly. Considering the front only, for disc brakes you need to build proportionally beefier lower left fork legs, and tune the flex of the fork differently. For cantis you need to reinforce the fork at the bosses to reduce spreading under braking, and the fork crown needs to be beefier. Properly designed, weight should be equal.
one day the advantages will outweigh the disadvantages for CX like they have for MTB.
DirtyWorks said:We generally agree, but a couple of nits to pick.
1. The advantages disc brakes have in mountain bikes exist because of the sum of rougher and faster courses, fatter tires and suspension. A cross course will never be as rough and won't be as fast. The 'cross bike doesn't have fat tires or suspension either. (Suspension tears up the courses too)
2. The UCI also set the fattest tire limit at about a 32c tire. Even if there was some constant benefit to discs, the skinnier tire doesn't make discs an overwhelming good now or in the future.
#1 and #2 are critical issues the ignored in the rush to discs. Boom/Nys/Stybar races will not be tilted for/against because one of them is riding last year's cantilever equipped bike.
3. For the front disc, there is the small matter of the disc brake forces loosening the skewer. Unless they put the caliper in a different position, the same problem mountain bikers had will plague 'cross for a while. I make this point to remind readers that the switch to disc will include expensive design failures for a while.
4. The 'properly designed' argument is perfectly circular. I can make almost any design case and rationalize it with 'properly designed.' Ex. A 'properly designed' mountain bike will have 12" of travel front and rear and weigh 7 kilos. How come I can't buy one now?
dsut4392 said:Disc hubs are heavy, granted but they can be made lighter - the weight weenies just haven't got there yet. As you say, rotational weight can drop, and that's where it's at in terms of noticing the mass under acceleration.