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  1. #1
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    adjusting dia compe G brakes

    My 1985 Nishiki has the dia compe G brakes. The side that the cable is on does not return after I pull the brake. I've loosened the center bolt and it still does this. There is a flip lever just below the cable adjuster and if I move it down so the brakes are wide apart, I can assure it won't rub, but that is not a good fix.I keep centering the brakes but hit the brakes and the cable side brake pad stays put on the rim. Is the washer between the calipers going bad? I've oiled the area without improvement. How do you use the cable adjuster? These are side pull brakes. My front one works great. I can not imagine the spring going bad.
    YouTube has not been a help.
    Thanks

  2. #2
    wim
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    Don't have that brake here, so have to guess.

    First, make sure the nut at the red arrow is reasonably tight, then grab the whole brake with both hands and center it while pulling it open simultaneously.

    If that doesn't work (good probability it won't): in the space the yellow arrow points to, look for a hex nut or a thick spacer with two flats on it. Grab the nut or spacer with a thin wrench (could be 12,13,14 mm; cone wrench is ideal) and center the brake by turning the wrench one way or the other.

    If there's nothing to grab with a wrench, you might have to resort to the "somewhat controlled spring tension adjustment" method. One way is to unhook one spring arm and pull it forcefully away from the brake, increasing tension on that side. The other way is to whack (often, several times) one spring arm using a modified screwdriver and a hammer. That decreases tension on that side. To modify an old screwdriver into an impact brake spring tension adjustment tool, grind or file a notch into the blade so it can't slip off the spring arm and go into your tire. Don't ask me how I know about this. Edit: No file or grinder: use something blunt on the brake spring.
    Last edited by wim; 08-08-2011 at 09:20 AM.

  3. #3
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    There's never a need to beat up the springs. If the brake arm pivot is loose and well lubricated to allow free movement, the brake can be centered by rotating the pivot bolt and holding it there when tightening the mounting nut.

    Two other things can affect brake centering.

    The first is friction where the spring arm meets the brake arm. As the brake opens and closed there's a bit of sliding at this point, so a drop of oil is needed to keep the spring sliding freely.

    The other is the push pull of the cable itself, usually more of a problem with shorter frames. The short loop can pull up the arm if too short, or push it down if too long. You can compensate by turning the pivot bolt more, but I to cut cables to a neutral length to avoid pushing or pulling more than slightly.
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  4. #4
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    Thanks. I did not think I needed to touch the bolt behind the fork. Just thought the front nut was screwed onto it. So I'll try that. What does the threaded screws do just above the lever on the right?
    I'm may just take them all off and see if a washer is wearing out.

  5. #5
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    Quote Originally Posted by osteomark View Post
    Thanks. I did not think I needed to touch the bolt behind the fork. Just thought the front nut was screwed onto it. So I'll try that. What does the threaded screws do just above the lever on the right?
    I'm may just take them all off and see if a washer is wearing out.
    The front nut and locknut adjust the play on the arms. You want as close as possible to zero play with the arms free to open without sticking. The spring passes through a block attached to the center bolt, so loosening, centering and tightening the bolt is what's needed.

    The cable adjustment is done by way of the knurled barrel the cable passes through. You turn the barrel up to tighten the cable and bring the arms in, then bring the little ring down to lock it in that position. The QR lever below that is to open the arms enough for the tire to pass freely when changing the wheel.

    Don't forget to oil the spring/arm stops.
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  6. #6
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    If the brake has not been taken apart for cleaning after all these years, this will probably be a good time to clean the grime and grit out. At 26 years, I'd have them apart for a thorough cleaning. They are not complex to take part, clean and lubricate. Just take note of washer placement. As mentioned, a drop of oil usually works if the caliper is not to dirty.

    Next is the cable, if it is equally as old, it is likely worn and or if there was a lubricant in the housing, it is now gummy and causing it to stick. Replacing them is easy and this is my thought on the caliper not returning fully.

  7. #7
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    Quote Originally Posted by wim View Post
    .....If that doesn't work (good probability it won't): in the space the yellow arrow points to, look for a hex nut or a thick spacer with two flats on it. Grab the nut or spacer with a thin wrench (could be 12,13,14 mm; cone wrench is ideal) and center the brake by turning the wrench one way or the other. .....
    It is a bushing with cutouts machined into it as a holder/support for the caliper's spring. It also has two flats machined onto the sides to allow centering with a brake wrench. Park's version is flat like a cone wrench, but with the open jaw of the wrench at a 90 degree angle to the handle. I think it's either a 10mm or a 12mm. The cheaper, more common version of that Dia-Compe brake lacked a quick release & the machined flats on the bushing the 'G' has, and are harder to center.

  8. #8
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    Much better. I loosened the not behind the frame and move the calipers back and forth and now working. Today I test the Trek 1.2. 56cm and 54cm.Thanks again everyone!

  9. #9
    wim
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    Quote Originally Posted by osteomark View Post
    Much better. I loosened the not behind the frame and move the calipers back and forth and now working. Today I test the Trek 1.2. 56cm and 54cm.Thanks again everyone!
    So after I typed my fingers sore, you're going to ditch the Nishiki and get a modern marvel of bike technology? Just kidding—have fun testing the bikes!

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