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Old 07-18-04, 03:28 PM   #1
javajo
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Rear Brake Centering Adjustment

Hello All -

I've got a '01 Specialized Expedition Sport. I'm a bike repair novice but I enjoy getting my hands dirty. When I blew my rear tire out, instead of paying $12.00 for my bike shop to repair it, I instead spent $10.00 on two replacement tubes, and went about the task of repairing it myself. Armed only with "Zinn and the Art of Bicycle Maintenance" and a few tools, I went to work. Getting the tire off was no problem. Getting the new tube installed was no problem. Getting the rear tire back on the seat stay was a bit of a challenge - first time it wasn't centered. Re-engaging the rear V-Pull brakes was a bit of a hassle, but not bad. However, I think I screwed up the rear brake allignment in the whole process. I re-positined the brake pads so they are even with the rims. Now however, it seems the brakes are off center. When I pll the front lever, only one arm of the brakes seems to fully engage. The other side rubs the rim. I can move the whole rear mechanism back and forth but it doea not stay centered. I tried adjusting the springs by disengaging them from the retension pins and bending them out, then putting them back. I also fooled with the spring adjustment screws on each side with no sucess.

Any ideas how to fix this problem?

Thanks much for any help!
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Old 07-18-04, 03:44 PM   #2
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Expedition Sport, huh. Is there any writing on the brake arms?

If the brake arms say ProMax on them, you'll be doing yourself a big favor by throwing them away and replacing them with a Shimano or Avid product.
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Old 07-19-04, 07:16 AM   #3
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Originally Posted by Retro Grouch
Expedition Sport, huh. Is there any writing on the brake arms?

If the brake arms say ProMax on them, you'll be doing yourself a big favor by throwing them away and replacing them with a Shimano or Avid product.

Good Morning -

I'm not sure what brand the brakes are - according to the specs - the brand name is not listed.

Any idea how I can fix the set that I have at least for now.

I really didn't plan on upgrading any parts on my bike yet. It's barely a year old.

Thanks again -
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Old 07-19-04, 07:35 AM   #4
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OK, try this:

1. Disconnect the cable that commects the two brake arms. If you squeeze the two arms together, you should just barely be able to lift out the metal noodle that the cable runs through. If you didn't do this when you initially took your wheel off - start.
2. Make sure that your wheel is solidly bottomed in the dropouts. IMPORTANT!
3. Use a 5mm allen wrench to loosen up each brake pad in turn. Push the arm against the rim and tighten the arm so that the pad is flush with the brakeing surface of the rim. Even better is to have the front of the pad hit just a "skosh" before the rear.
4. Now reconnect the cable that joins the two arms.
5. Examine the space between the pads and the rim. Are the two spaces equal? Fiddle with the spring tension screws on each brake arm until they are.
6. Watch the arms as you pull the brake lever. Do they move exactly together? If not, fiddle with the spring tension screws some more.

With average luck and decent components, that will fix it. Good luck!
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Old 07-19-04, 07:45 AM   #5
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Originally Posted by Retro Grouch
OK, try this:

1. Disconnect the cable that commects the two brake arms. If you squeeze the two arms together, you should just barely be able to lift out the metal noodle that the cable runs through. If you didn't do this when you initially took your wheel off - start.
2. Make sure that your wheel is solidly bottomed in the dropouts. IMPORTANT!
3. Use a 5mm allen wrench to loosen up each brake pad in turn. Push the arm against the rim and tighten the arm so that the pad is flush with the brakeing surface of the rim. Even better is to have the front of the pad hit just a "skosh" before the rear.
4. Now reconnect the cable that joins the two arms.
5. Examine the space between the pads and the rim. Are the two spaces equal? Fiddle with the spring tension screws on each brake arm until they are.
6. Watch the arms as you pull the brake lever. Do they move exactly together? If not, fiddle with the spring tension screws some more.

With average luck and decent components, that will fix it. Good luck!

Thanks Retro Grouch -

When I initially took the tire off I diconnected the brake cable - However, I think that the tire bumping against the brake mechanism during the disassemble and reassemble simply through everything off kilter.

Can you elaborate on step (3). I understand how to allign the brake pad but how do you tighten the arm?

Thanks again!
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Old 07-19-04, 08:16 PM   #6
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Did you make sure you reseated the noodle correctly?
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Old 07-20-04, 08:19 AM   #7
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Did you make sure you reseated the noodle correctly?
Yes - it appears to be seated correctly.

I have a suspicion my wheel is off. This all started with a flat tire....

Is it possible when I installed the new tube, something with the wheel became off kilter?

When I spin the rear wheel, it rubs against the brakes in certain areas of the rotation. I've made sure the wheel is seated properly in the seat stays...the first time the entire wheel was shifted to the right - it should be fine now...

One thing I still don't understand about V-Pull brakes...

You can shift the whole mechanism left and right simply by moving it with your hand - when you shift it right, the left pad hits the rim, when you shift the whole mechanism left, the right pad hits the rim.

Does this naturally straighten itself out when the brake lever is squeezed?
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Old 07-20-04, 09:28 AM   #8
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In my eariler post, when I spoke of tightening the arm, I ment retighten the brake pad assembly onto the arm.

I doubt you could have damaged your wheel just by changing the inner tube. It is possible, however, that whatever caused your flat might have also damaged your rim. If your wheel wobbles when you spin it, I'd have a shop take a look at it. The brakes are never going to work at their best if you have a wobbly wheel.

Each linear pull brake arm has a spring that tries to pull it away from the rim. Since the same cable is used to pull the two arms together, the cable tension on both arms will always be equal. If the tension from both springs is also equal, the arms will automatically move together. When guys talk about using the little screws on the arms to center the brake, what they are really doing is equalizing the spring tension on the two arms.
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Old 07-20-04, 09:37 AM   #9
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Quote:
Originally Posted by javajo
When I spin the rear wheel, it rubs against the brakes in certain areas of the rotation. I've made sure the wheel is seated properly in the seat stays...the first time the entire wheel was shifted to the right - it should be fine now...

One thing I still don't understand about V-Pull brakes...

You can shift the whole mechanism left and right simply by moving it with your hand - when you shift it right, the left pad hits the rim, when you shift the whole mechanism left, the right pad hits the rim.

Does this naturally straighten itself out when the brake lever is squeezed?

Sounds like your wheel is either out of true or it's not seated quite straight in the dropouts... As far as the brakes go: yes. Ideally, the spring tension in each arm should be equal; if this is the case, the brakes will self-center.
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Old 07-20-04, 09:44 AM   #10
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i had the same problem with my rear brakes when i got my bike back from the lbs..
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