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Cantilever brakes(6 posts)

Cantilever brakeskechinbo
Jan 18, 2004 11:47 PM
I'm perplexed...I have an older GT (Karakoram, I think) Cro-Moly frame that I'm converting to a dedicated singlespeed. I ordered a set of V-brakes for it and the front fit just fine on the original, stiff fork, but the rear don't fit over the braze-on brake studs...they are larger than the holes in the brake arm. Closer observation also reveals that the rear does not have the little 3-hole plate that the tension spring of a V-brake engages with. HMMMMM....right about now I'm thinking that frame (which I just got EBay for $50) might have been older than I thought. The markings on the bottom bracket shell seem to indicate that it was made in 1989!!! Anyhow, here's my questions:

1) Could it have originally had V-brakes on the front and cantilevers on the back?

2) Were the brake studs for cantilever brakes larger in diameter that the studs for V-brakes?

I've been mostly a roadie for the last ten years and recently got into MTB....I also love the look and simplicity of single speed so I converted my GT Avalanche to SS and am having a blast. Unfortunately, I also miss having the ability to hit the steep trails so I'm putting my Avalanche back to the original geared set-up and building this dedicated SS urban assault, beer run, grocery getter, riding with the kids thing. I have ground the cable bosses off and shot the whole thing in ultra flat black (Krylon, $3.98 a can). Everything else is coming along nicely but this rear brake thing has me feeling really inept. Any input would be appreciated.

Matt
Couple of thoughts.Spoke Wrench
Jan 19, 2004 6:38 AM
1. I don't remember the exact year when linear-pull brakes came out, but I'm pretty sure that 1989 will pre-date them.

2. What do you have for top tube cable stops? Linear pull brakes require a section of cable housing. That usually means a cable stop on the top tube. Five years ago or so it was fairly easy to purchase a clamp-on top tube cable stop, but that was never a real common piece and may it be hard to find one today that's the right size. You can run a cable housing all the way from your lever and zip-tie it to the top tube, but it's ugly that way.

3. Most canty brake studs actually screw into the frame. As you have already discovered, they're not all exactly the same so you have to get the right size. That's an easier part to break than you might imagine so I'd think the frame designer would have made them replaceable but I haven't done a ton of work on old GTs.

4. Where, exactly are your canty studs? About that time several manufacturers installed a U-brake on the chain stays. They were a ROYAL PITA to set up and adjust! If that's what you have a linear pull will never work because the studs will be in the wrong place for the pads to line up.

Good luck.
Couple of thoughts.kechinbo
Jan 19, 2004 7:06 PM
Thanks for the input....to answer your questions - the top tube has an internal brake cable which enters on the left side up front and exits at the center, bottom (6 o'clock position) in the rear. The studs appear to be exactly where V-brake studs would be and they're not screwed in or mounted down on the chain stays. Another reader suggested placing a rim on the frame to determine exactly where the studs are....even with the rim or slightly below....will try that test next.
re: Cantilever brakeslaffeaux
Jan 19, 2004 8:19 AM
V-brake and canti bosses are identical, so that is not the issue. However, GT used rear U-brakes up until '93 or so (they were the last MTB company to move away from u-brakes), and u-brake bosses are different from canti bosses.

To check to see what you have, install a wheel or rim on the bike. If the bosses are located below the rim (i.e. closer to the hub) it's a canti boss. If the bosses are located above the rim then you have u-brake bosses.

In either case check to see if there is an extra sleve on the bosses. Come cantis come with these (for example Paul brakes). If the frame is set up for u-brakes, start looking on eBay for a set of u-brakes or roller cams, both of these use the same mounting points.
re: Cantilever brakeskechinbo
Jan 21, 2004 2:49 AM
Thanks for the advice....I mounted the rim and sure enough, the bosses are above the rim. Guess I'm looking for a U-Brake.

Matt
U-brakeMShaw
Jan 19, 2004 10:39 AM
I have an old GT sitting in my garage with a U-brake on it. If you need it (assuming it IS a U-brake mount) let me know.

email me at mikeshawTWO@cox.net by replacing the TWO with 2

Mike