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Dia Compe Cantilever Brakes Adjustment

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Dia Compe Cantilever Brakes Adjustment

Old 07-13-13, 09:33 AM
  #1  
Leaozinho
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Dia Compe Cantilever Brakes Adjustment

Hi everyone,

I recently bought a Bianchi Volpe used for a great price, only problem was the front brakes were really in need of some adjustment because they weren't clamping tight enough to cause the wheel to stop. I've never worked with cantilever brakes before and ended up just making the problem worse when I tried to work on them - now one side is always rubbing against the rim. I know at this point, especially for someone inexperienced like me, the best thing to do would be to take it into the LBS. But I want to take this bike out on a tour and would really like to understand how to fix and make adjustments on the brakes should any problems arise. I approached one place and offered them some extra money to let me watch them fix it, which was turned down. So I'm at a loss - I didn't find much help online in the way of tutorials/videos, and I did check out Sheldon Brown's site to no avail. Is it better to just give up and take it in and continue being a helpless idiot (haha)?

As always, thanks guys - you are all very helpful.
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Old 07-13-13, 09:58 AM
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Dia Compe used various systems over the years to adjust spring tension balance. One that might not be obvious is the rotating spring cam on one arm. Look for something with wrench flats behind either brake unit. If you have a part like that, it's the spring cam which is turned to adjust spring tension.

Put a thin wrench (some are 19mm, but I don't know that all are) onto the cam, loosen the mounting bolt, rotate cam to center the brake, and retighten mounting bolt to keep it there. This is a nice system which affords a wide range of adjustability, but it may take you a few tries to get it just right.

Also, make sure both arms are well oiled on their pivots, since pivot friction can change and keep one or the other arm from opening. (oil pivots first, since this often changes the spring balance).
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Old 07-13-13, 10:08 AM
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I suspect you should buy new brake pads then adjust the cables
so the pads meet the rim with just the right amount of lever travel.
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Old 07-13-13, 10:57 AM
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What model of Dia Compe canti lever brakes are you using?

If you are using the 987 canti lever brakes, the spring tension is through the 13mm nut that is behind the brake arm. You have to loosen the 5mm allen bolt that is holding the brake arm to the fork, insert a 13 mm open spanner and pull it downwards, then tighten the 5mm allen bolt while holding this spanner in position. Now repeat for the other side.
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Old 07-13-13, 11:16 AM
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I'm sorry for not including this before - they are the 984 series. I think the cable/pads are good - I just messed it up pretty bad trying to work on it myself. Anyone have any suggestions for the 984?
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Old 07-13-13, 11:20 AM
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Originally Posted by Leaozinho View Post
I'm sorry for not including this before - they are the 984 series. I think the cable/pads are good - I just messed it up pretty bad trying to work on it myself. Anyone have any suggestions for the 984?
Same answer as before. If the issue is spring balance (opens unevenly or one arm doesn't open) use your own eyes and look for the spring adjustment cam (thanks to TiBikeGuy, we know it could be 19mm or 13mm). If there is any thin hex shaped part between the brake and frame, that's how you adjust the spring. Also, some later brakes, ie 988, have the adjustment cam in front, in the form of a trim piece with 2 wrench flats under the mounting bolt. Same method for adjustment as if they're in the rear.

Otherwise springs are usually adjusted by small screws bear the pivots of each arm (don't think your 984 brakes are this way).
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Last edited by FBinNY; 07-13-13 at 11:23 AM.
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Old 07-13-13, 02:49 PM
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Thanks guys - found the cam (which is indeed on the front) and will spend some time with it tonight. My question now is that I screwed around with some other variables and don't know how to properly reset them. I'm talking about the height of the transverse cable (I adjusted that by loosening and raising the yoke holding the transverse cable to the main cable - forgive me if I'm not using the correct terminology), and also the amount of cable passing through the one brake arm. I messed around with both of these things in my initial attempts at a fix...
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Old 07-13-13, 03:26 PM
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Originally Posted by Leaozinho View Post
Thanks guys - found the cam (which is indeed on the front) and will spend some time with it tonight. My question now is that I screwed around with some other variables and don't know how to properly reset them. I'm talking about the height of the transverse cable (I adjusted that by loosening and raising the yoke holding the transverse cable to the main cable - forgive me if I'm not using the correct terminology), and also the amount of cable passing through the one brake arm. I messed around with both of these things in my initial attempts at a fix...
There's no one answer when it comes to yoke cables. IMO you get the best overall action when the yoke meets the arm at right angles when the shoe meets the rim. This means that the tension is pulling the arm closed at that point rather than pulling it up. Beyond that you'll get more leverage (usually) with a shorter yoke, and less with a longer one, but you need to balance that against tire clearance, and brakes that open far enough.

So start with the yoke meeting the arm square, and tighten the pinch bolt enough to do a gentle test squeeze to see the lever throw, and gauge how far the brake opens. Feel free to go shorter if you want, especially with new shoes since shoe wear will change the geometry, making the yoke effectively longer.
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“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN

WARNING, I'm from New York. Thin skinned people should maintain safe distance.
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