Technical FAQ: road brakes
It was interesting to see that Kittel’s bike has linear pull brakes. I’ve often wondered why these never showed up on road bikes, since they were so simple and effective on mountain bikes. Are these likely to become more common on road bikes, and if so, why did it take so long? I’m curious about their pluses and minuses versus more traditional dual pivot offerings.
Little, integrated V-brakes have been around for awhile; some Ridley and Storck road bikes have had them for a number of years. They came along in the push for improved aerodynamics, since you can tuck them in tightly to hide them behind the fork legs and seatstays. Because of the high interest in (read: sales of) aero road bikes, I imagine you’ll see more of them.
It took so long because of a concern that consumers would reject a bike that they couldn’t mount standard brakes on, as well as a concern that consumers would not trust components from a bike brand. For instance, would you be likely to believe that derailleurs designed and built by a bike brand would shift as well as those from Campagnolo, Shimano, or SRAM? I would guess not; you are more likely to trust that a bike brand’s engineering focus is entirely on producing the best frame and fork, and you might assume that any components it makes would be more of an afterthought done to optimize the frame or fork design.
It can happen now because consumers are getting used to proprietary parts on bikes. Car brands have long been this way — a Subaru alternator or brake caliper won’t work on an Audi, or vice versa, and bike and component brands are increasingly working from this “system” perspective. If consumers can accept an odd-shaped seatpost or a seat mast requiring parts supplied only by that bike manufacturer, or a bottom bracket or integrated headset design unique to that bike brand, then the thinking goes that it’s not such a stretch that they might be willing to accept a new brake standard. Little linear-pull road cantilever brakes (a.k.a. V-brakes) generally mount on integrated cantilever bosses or some other integrated mount and do not mount on a standard brake center hole.
Our experience has been that the power of integrated road V-brakes is good, and their modulation is less than optimal. We have not done a Velo brake test that included them (yet).
My 10-speed Shimano 7800 levers seem to have packed. No amount of tinkering results in a good gear change through the cassette from top to bottom and back again. I presume the internals are worn. This is my spare/training bike, so I want to keep it running at minimal cost. Will the remaining 7800 brakes and derailleurs work with 6700 or 5700 levers?
Dura-Ace 7800, the last Dura-Ace group to have the shift cable sticking straight out of the side of the lever body, has higher-leverage brake levers than current Shimano STI levers, which have the shift cables concealed beneath the handlebar tape. So, Ultegra 6700 levers or Shimano 105 5700 levers will not work ideally with your 7800 brakes. They will get the pads to rim faster, as they have more cable pull, but they do not have enough leverage to pull the 7800 calipers the way they were meant to be pulled; the 6700 and 5700 levers are designed for higher-leverage brake calipers than the 7800 calipers. The brakes will still work, but your hands will be doing more of that work.
The shifting will be fine; 7800 derailleurs will work with 6700 or 5700 shifters.
Any tips on how to prep multiple disc wheelsets for cyclocross? Specifically, I’m asking about getting each of them bedded in. I have been assuming that the bedding process not only lays down material from the pad to the brake, but also scores the pad to interface with the rotor. I imagine that even if running the same rotors on all wheelsets (a costly option), that nothing will ever mate up the exact same.
Would you just go through the 6-10 stops from speed with each wheelset before the beginning of the season and then hope for the best after a pre-race wheel swap?
On my own disc-brake bikes, I have simply gone through the normal bedding-in process with my various wheels, and, I must admit, it never occurred to me to worry about whether they bedded in differently. Rather, the concern I had was about getting the rotors to all line up exactly the same between the pads, so that if one wheel’s rotor cleared the pads, then the rotors on all of the other wheels for that bike also would not rub the pads. I have often cut my own rotor spacers out of beer cans to get the rotor location as precise as I could from wheel to wheel.
On both my disc cyclocross bike and my mountain bikes, I frequently switch wheels and quite frankly never noticed a braking difference, regardless of whether the various rotors were of different brands or not.
With all the talk about road disk brakes — some making the case for their superiority in modulation in difficult weather conditions, others lamenting the extra trouble of wheel changes and safety hazards during crashes — I’ve wondered why no manufacturer has thought of what appears to be a relatively simple compromise between disk brakes and conventional rim brakes: a larger brake pad and slightly larger rim braking surface. Suppose we were to simply double the height of a conventional brake pad, make the pads more like shoes, and increase the rim braking surface to accommodate this increased surface area. At the same time, the braking surface could be scored with some channels to carry away the water or dirt, like on a rotor. There might be an increase in weight, but compared to some of the medium profile aluminum rims already in use, probably not a lot if they could simply be reshaped. Would this not be a simple way to enjoy a good deal of the benefits of a disk brake without its shortcomings?
I suppose it is possible to even design a piston-type caliper for rim brakes but this might not even be necessary to achieve some important benefits. What are your thoughts on this? For example, would heat dissipation over the larger surface area be a problem?
Rim brakes already enjoy a massive advantage over disc brakes in sheer diameter; no brake rotor is as big around as a rim. I don’t believe that increasing the pad size and height of the braking surface would make a fundamental difference. One thing that it might do is allow the pads to run cooler, but I suspect that total heat going into the rim would be about the same. And merely lengthening the pads and pad holders could achieve a similar result.
It’s not often with aluminum rims that you melt the pads. It can certainly be an issue with carbon rims, but making the braking surface taller on a carbon rim would come with a significant weight increase, as the material used on the braking surface is added to protect the structural carbon below. Consumers of carbon rims spend the big bucks and choose to suffer less effective braking in order to get low weight.
Scoring the rim braking surface was long ago abandoned as a bad idea. It eats brake pads. The only rims that have that are chromed steel rims—to increase friction on such an otherwise slick surface.
And dirt and water stay out of disc rotors primarily because of location, not design of cutouts. The tire simply does not drag water and muck into disc brake pads the way it does with rim brake pads.
As for piston-type rim calipers, those already exist, and I just put a pair back on my bike after the SRAM recall. Here are the original ones on my bike; these were recalled, and the new ones feel just the same. Yes, they are great brakes, but they are not so much better as to be a game-changer relative to cable-actuated rim brakes. Furthermore, Magura has been making hydraulic rim brakes for around a quarter of a century, including road-specific ones. The pair on my tandem has been on there since the 1990s. Again, they’re great, but not so much better that they made cable-actuated rim brakes obsolete.
I recently built up my dream road bike, and when I went to take it on its maiden ride, I experienced awful brake chatter when I used the front brake at speed. I built the bike up with a new Easton EC90SL fork, Ultegra 6800 brakes and 25c continental GP4000s II clinchers mounted to a custom wheelset using Stans Alpha 340 rims. I was stumped as to where the chatter and vibrations were coming from. I then inspected the fork and noticed that the tire clearance was very slim. I swapped out the front wheel for a wheel clad in 23c rubber and did some fast brake tests. Problem solved! No more vibrations or chatter. I guess the 25c rubber was hitting the fork under braking.
If anyone is experiencing brake chatter, such as in this column of yours, then perhaps they need to check how much tire clearance they have on their front fork and go a size down.
Regarding latex tubes:
With regard to your and Challenge’s answer about latex tubes (although this trick works for all tubes). To lightly inflate the tube prior to installing (Challenge says: “lightly inflating the tube exactly to the point where it first forms its toroidal shape with no extra pressure”), simply blow into the valve with your mouth. Easy, fast and impossible to inflate too much!