Take the 2-minute tour ×
Bicycles Stack Exchange is a question and answer site for people who build and repair bicycles, people who train cycling, or commute on bicycles. It's 100% free, no registration required.

Questions

Q1. For rear cantilever brakes, are there any off-the-shelf parts or brake designs that route a rear brake cable from underneath the saddle cable instead of above?

Q2. If not, then can anyone suggest an improvised, but proven setup using existing, readily-available parts?

Q3. What concerns should I have with a reverse-pull cantilever brake setup (e.g. safety, maintenance)?

Background

I have a mixte frame with standard rear cantilever brake bosses on the seat stays, with standard cantilever brakes such as these:

classic wide cantilever brakes

Since the frame is a mixte, the rear brakes are higher than the "top tube" of the mixte, along which runs my rear brake cable.

I've seen that some mixtes use a reverse cable attachment to side-pull caliper brakes so that the cable makes a single arc from the top tube to the brakes. My goal is to roughly mimic this cable routing, but with cantilever brakes instead. Here is an example (but mine does not have a rack to work around):

a reverse-pull caliper brake setup

The original build is pictured below (not the actual bike, but same model, etc.) and has the rear brake cable running along the "top tube", curving along the back of the seat tube, and then going over a pulley that is attached to the seat tube clamp bolt. That pulley acts as a housing stop and so it's a center-pull from the top. I am looking to improve the rear brake responsiveness, put less stress and wear on the cable, and have fun engineering a more elegant solution.

Schwinn Mirada rear brake setup

share|improve this question
1  
How is it routed originally? Is this a new build? –  WTHarper Nov 1 '13 at 19:38
    
@WTHarper, I added the route of the original build into the question. I hope that helps, thanks! –  PositiveK Nov 1 '13 at 20:26
1  
The pulley approach is the most obvious and straight-forward solution to this. Another option would be to wrap a long straddle cable around a tubular form placed roughly where the mirror mounts in the lower picture, then have the "junction" of the cable meet the main cable about midway between the upper and lower seat stays. (Using pulleys would constrain the cables horizontally too much, but it's hard to say how much friction would be in a roughly 1" radius curved shape.) Or you could maybe somehow use two "noodles" from V brakes. –  Daniel R Hicks Nov 6 '13 at 22:56
add comment

1 Answer 1

You can't do this with traditional cantilever brakes, because the straddle wire has to be pulled from above to tension it - attempting to pull it from below would pull into the wheel.

You could pull from the side by using direct pull cantlievers, a.k.a. v-brakes. A Problem Solvers "Travel Agent" could probably be hacked up to work, and a clean implementation could probably be done with one of the no-longer-produced World Class "V-Daptor" adapters, if you could find one.

That said, both of those approaches are probably less elegant than the already-existing pulley method that it sounds like already works on the frame.

share|improve this answer
1  
I was thinking that a V brake would be the way to go. Maybe one could modify the noodle to pull from below somehow... –  WTHarper Nov 2 '13 at 22:04
    
@WTHarper: Yeah! Exactly my original improvised plan. I am going to try the noodle attached to the transverse cable yoke, and run the bare cable up to a standard cable hanger at the seattube clamp where it will have a little cable clamp to hold it fixed. There is the issue of clearance as lantius mentioned: between yoke and tire, but also considering the metal reflector bracket that sits between tire and yoke. –  PositiveK Nov 6 '13 at 20:17
1  
@WTHarper Update: I removed the cable anchor bolt from an old aluminum saddle cable hanger. I bent the bolt hole towards the side with the curled lips that hold the saddle cable, to a 90 deg angle. I inserted a noodle's tip into that to create the lower pull point as discussed above. However, the noodle bend bumps into the hanger causing the cable to emerge from the noodle at a slight angle instead of straight out. This made it rub against the noodle's sharp tip edge. So I abandon that approach until I find a piece/way to attach the hanger further down to leave clearance for the noodle. –  PositiveK Nov 22 '13 at 1:40
    
Interesting...photos would be great! –  WTHarper Nov 22 '13 at 1:58
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.