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Technical FAQ: Road discs and other brake issues

  • By Lennard Zinn
  • Published Aug. 28, 2012

Editor’s Note: Lennard Zinn’s regular column is devoted to addressing readers’ technical questions about bikes, their care and how we as riders can use them as comfortably and efficiently as possible. Readers can send brief technical questions directly to Zinn.

Dear Lennard,
This e-mail is in response to your recent column about road disc brakes. I used to work at a store that sold tandems and was one of the nation’s first Volagi dealers. During that time I experimented with nearly every conceivable combination of rotors, pads, cable housing and calipers on road disc brakes. Here is what I have found:

The newer style Shimano levers (6700, 7900, etc.) require MTB BB7′s to properly function; there is not enough stopping power with the road BB7′s.

Avid Compression-less housing is a must.

Organic pads work far better than the sintered metal pads that come stock in the BB7′s.

While not light, Shimano Ice-Tech rotors seem to work the best (you have to bend the little tabs on the brake pads to keep them from interfering with the aluminum spider). They are also very quiet.

Proper alignment is best done without the cable housing attached to the caliper. On many bikes the cable housing will push the caliper to the side once the mounting bolts are loosened making proper alignment impossible.

Even with everything set up perfectly, the brakes will still be less powerful when compared to rim brakes. The best solution I’ve found is to pull on the brakes harder. You can really get on them without worrying about locking them up.
— Matthew

Dear Matthew,
Thanks for your very useful letter from the trenches of disc brake setup on road bikes.
― Lennard

Dear Lennard,
I built up a cyclocross frame as my winter bike. I used Tektro BMX mini-V brakes in lieu of cantilever brakes. The stopping power and modulation is fantastic in my humble opinion. They work fine with STI levers. I do use KoolStop pads. I wonder why this is not considered as an option instead of disks. A cross fork would work well on most frames. I have not tried a front mini V and a rear side pull, but I imagine that that combo would also work well.
— Dave

Dear Dave,
I’m not sure in what vein you’re asking this question. Do you mean as an alternative to disc brakes on a road bike? In that case, you’d be better off with a good road rim brake—lighter and more aerodynamic than a V-brake, good modulation and power, works with standard road fork, etc. And sticking a cyclocross fork on a road bike would tip it back, decreasing the head and seat angles and raising the bottom bracket (and the handlebars) – not things most serious road riders would want.

Or do you mean as an alternative to discs on a cyclocross bike? I have in this column recommended a front mini V-brake for those riders who have fork chatter with cantilever brakes, as it eliminates the flex in the steering tube from the braking equation. However, it’s not a perfect solution for cyclocross, because of the minimal clearance the V-brake offers relative to a cantilever brake. Because of the long V-brake arms, even on mini V-brakes, you get high leverage at the expense of pad travel. Since the pads don’t move very far with the lever pull, they stay very close to the rim, and the arms themselves are also close to the tire, as is the link over the tire on mini V-brakes, all of which makes for considerably less mud clearance than a cantilever brake. In some areas of the country, this is a big consideration.

Another issue is that the brake power with a mini V is almost too much with most road levers other than the newer style Shimano levers (6700, 7900, etc.), whose leverage is lower and cable pull is higher than standard levers. I ran a TRP mini V-brake all season last year on the front of one of my cyclocross bikes (see photos) to get away from the fork chatter I had had with cantilevers on it. I was using a standard Cane Creek left road lever (single front chainring, so no brifter). In order to not end up on my nose when pulling the brakes in a hurry, I had to back the cable tension way out so that the brake didn’t come on until the lever was almost all of the way to the bar. If I did not, the front brake came on so much harder than the rear brake or than either brake on my other bike. In the heat of the moment in a race, especially after taking a bike change, I could easily brake too hard on the front.

Furthermore, like a V-brake, a disc brake also eliminates the fork chatter problem of cantilevers, and it offers the best mud clearance of any of the options. So, other than perhaps for weight reasons or cost reasons, I don’t see a mini V as a favorable option to a disc brake in cyclocross.
― Lennard

Dear Lennard,
In response to Paul Lew, director of technology and innovation at Reynolds Cycling, to make this statement about using approved brake pads, it would be fair to assume Reynolds must have tested the other available brake pads with its rims. If they have not done this, it would be a fairly straightforward and easy test. If they have not done this, it is impossible for Paul to make these statements fairly. Therefore, can he publish or produce these results (that’s how science works) to substantiate his claims? I am sure to make these claims he will have done this and be only too happy to produce the tests.
— Derek

Answer from Paul Lew:

You are correct to assume that testing brought me to the statement that I made. In 2008, when I joined Reynolds Cycling, of my many engineering efforts, one was focused on carbon (especially clincher) braking performance. I first tested commercially available pads (including the Yellow SwissStop pads that Reynolds Cycling had once promoted and that our sponsored grand tour team, AG2R La Mondiale preferred to use) to an unsatisfactory outcome. The outcome I hoped to achieve with commercially available pads was a pre-determined braking force, braking modulation and temperature value.

Based upon the unsatisfactory outcome, we began a two-year development program to define and manufacture a new brake track system (we branded CTg) and a new pad (we branded Cryo-Blue) with a chemistry that allowed us to achieve our target values. In the final analysis in 2010, the new CTg/Cryo-Blue System performed 38-50 degrees Celsius lower temperature than the other commercially available off-the-shelf rim/pad combinations we tested, so the decision to recommend the Cryo-Blue pads with our CTg rim laminate was an easy decision.

I recognize that the (clincher) brake track topic is front-and-center. In an effort to bring to light major issues surrounding this topic, this fall Reynolds Cycling will release a document that chronicles the history of the carbon tubular and clincher rim development from the perspective of braking performance, and it will be loaded with data. This document will follow the development of braking technology beginning in 1998 when I began manufacturing and selling carbon rims (including carbon clincher rims) under the Lew brand name, the migration of the technology to Reynolds Cycling in 2002, the engineering efforts and improvements by Reynolds Cycling from 2002 to 2010, and the details of the significant advancement the 2010 CTg and Cryo-Blue System represents.

This document will answer the question you asked as well as many questions you may not have thought to ask. Please watch our website for the document.
Paul Lew, Director of Technology and Innovation
Reynolds Cycling, LLC

Dear Readers,
I’ve been messing around further with this question:

Dear Lennard,

Regarding your statement: “As long as you have the pad holder oriented so the closed end is pointed forward and you don’t push the bike backward while the brakes are engaged, there is no force acting on the pads that will pull them out of the pad holders in normal riding.”

I used to think that until I tried to apply the front brake one day and got nothing. I don’t recall if it was one or both pads that had slipped out of my Ultegra SL 6600 caliper. I’ve never had any problem with the rear but my front retaining screws have been reinstalled. 
— Phil

I’ve changed my answer based on further investigation. I’ve found that under certain conditions I’ve been able to get my rear pads to come out when installed without the pad-retaining screws.

It was while waiting for my start at the Lookout Mountain Hillclimb in Golden, Colorado, on August 4 that I discovered it. The street that leads up to the stone pillars marking the start ramps up quite steeply for about a kilometer ahead of the start line. While sitting on my saddle with a foot down and my rear brake on to keep from rolling backward and chatting with friends, I noticed my rear pads slipping out. Indeed, if I put the brake on fully and sat down on the steep uphill, I could get both cork pads to slide completely out of the pad holders. I don’t tend to use the front brake to hold myself in place while chatting on an uphill, but maybe Phil does, and that could be the explanation for how his came out.

Anyway, in my original response, I passed it off as only able to happen if you push the bike pack with the brake on, an occurrence that seems rare to me. But if a hill is pulling you back, it could happen quite easily. Still, I have no retention screws in the pad holders on any of my road or cyclocross bikes, and other than this instance at the Lookout Mountain start line, I’ve never had one come out other than by me pulling it out.
― Lennard

FILED UNDER: Bikes and Tech / Technical FAQ TAGS:

Lennard Zinn

Lennard Zinn

Our longtime technical writer joined VeloNews in 1987. He is also a framebuilder, a former U.S. National Team rider, and author of many bicycle books, including Zinn and the Art of Mountain Bike Maintenance and Zinn and the Art of Road Bike Maintenance, as well as Zinn and the Art of Triathlon Bikes and Zinn's Cycling Primer: Maintenance Tips and Skill Building for Cyclists. He holds a Bachelor’s degree in physics from Colorado College. Readers can send brief technical questions to Ask LZ.

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