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Old 09-28-08, 10:05 AM   #1
rkrossi
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Centering brakes after reinstalling wheel. Why should I need to?

Every time I remove the front wheel and reinstall it, it seems like I have to readjust the brake trim screw to recenter the the pads relative to the rim. I would expect that since the skewer is just clamping the fork to the hub which should change from side to side, the rim would reinstall in the exact same position relative to the brake. The other possibility is that the hub is not seating in the fork dropouts in the same position so that wheel is at a slight angle relative to the forks. For that reason I always press down on the front of the bike before tightening the skewer.

This is the case with both of my bikes. Is there something that I'm doing wrong when installing the wheel or is this normal?
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Old 09-28-08, 10:17 AM   #2
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We all do this if we want our brakes working properly. Haven't got a theory as to why, it just needs done. bk
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Old 09-28-08, 10:19 AM   #3
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Originally Posted by rkrossi View Post
Every time I remove the front wheel and reinstall it, it seems like I have to readjust the brake trim screw to recenter the the pads relative to the rim. I would expect that since the skewer is just clamping the fork to the hub which should change from side to side, the rim would reinstall in the exact same position relative to the brake. The other possibility is that the hub is not seating in the fork dropouts in the same position so that wheel is at a slight angle relative to the forks. For that reason I always press down on the front of the bike before tightening the skewer.

This is the case with both of my bikes. Is there something that I'm doing wrong when installing the wheel or is this normal?
Are you sure you are putting the wheel back in the same way it came out? If you inadvertenly flip the wheel and it's off dish then it *will* cause the pads to become non-centered (assuming they were centered to begin with).

The other possibility is that you are inadvertenly bumping the brake out of position when reinstalling the wheel when the tire is being fit between the pads.
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Old 09-28-08, 10:47 AM   #4
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The other possibility is that you are inadvertenly bumping the brake out of position when reinstalling the wheel when the tire is being fit between the pads.


Thats probably the most plausible cause right there, in my experience. That and just flipping the release lever can decenter the brakes too. On dual-pivot brakes its as simple as adjusting the trim screw to get it back right. On campy single-pivot the caliper spring anchor acts as an adjuster and can be adjusted true with a 13mm bike wrench.
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Old 09-28-08, 11:09 AM   #5
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I notice the same effect on my bikes too. I have tried the following and it seems to help - put the front wheel back in - then apply the front brake - then tighten the quick release. Applying the front brake seems to help center the rim.
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Old 09-28-08, 01:08 PM   #6
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On dual-pivot brakes its as simple as adjusting the trim screw to get it back right. .
The function of the trim screw is not to center the brakes, it's to adjust the spring tension. Proper way to center dual pivot brakes is to grab the whole unit and move it by hand.
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Old 09-28-08, 01:08 PM   #7
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I notice the same effect on my bikes too. I have tried the following and it seems to help - put the front wheel back in - then apply the front brake - then tighten the quick release. Applying the front brake seems to help center the rim.
This is wrong, and should not be done. All it does is help NOT seat the wheel in properly in the droppouts.
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Old 09-28-08, 01:41 PM   #8
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The function of the trim screw is not to center the brakes, it's to adjust the spring tension. Proper way to center dual pivot brakes is to grab the whole unit and move it by hand.


http://sheldonbrown.com/gloss_dr-z.html#dualpivot


doesnt say anything about spring tension


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Old 09-28-08, 02:42 PM   #9
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http://sheldonbrown.com/gloss_dr-z.html#dualpivot


doesnt say anything about spring tension


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Thanks for the confirmation that you're a noob. Next please. And I've quoted the message so you can't deny it later.

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On dual-pivot brakes its as simple as adjusting the trim screw to get it back right.
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Old 09-28-08, 05:24 PM   #10
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Newer designs permit fine tuning the centering of the arms by simply turning a screw.
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Old 09-28-08, 07:01 PM   #11
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I notice the same effect on my bikes too. I have tried the following and it seems to help - put the front wheel back in - then apply the front brake - then tighten the quick release. Applying the front brake seems to help center the rim.
TERRIBLE idea not to mention un-safe. All that will do is keep the axle from seating down correctly into the dropouts.
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Old 09-28-08, 07:07 PM   #12
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I notice the same effect on my bikes too. I have tried the following and it seems to help - put the front wheel back in - then apply the front brake - then tighten the quick release. Applying the front brake seems to help center the rim.
Like everyone said- bad idea. But it works if you tighten the QR and then hold the brake as you flip the release closed.
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Old 09-28-08, 07:08 PM   #13
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Yep, agreed, Gary. Back in the 70's, I tried that trick and this was long before lawyer lips on the forks. I didn't get the axle properly seated and trashed my fork after I was showing off and riding a wheelie on my old 10 speed and the front wheel fell off as I was dropping back down. The QR hadn't tightened properly because the axle wasn't properly seated and aligned.
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Old 09-28-08, 07:13 PM   #14
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All in all I'd say your caliper bolt should be a little tighter. Also if, like mine in many cases, the release lever doesn't open up the pads far enough to let the tires get by so you have to wiggle, pull and pry then do what I did. I run the adjusters up closer to the top and when I need to remove the wheel I open the lever and also run the adjuster back down to open up the pads more. This lets me avoid the pullying and prying and the calipers stay put like they should.

While I don't mind using that trim screw for small adjustments if the arms are not all in line when I'm done then it's time to move the mount and move the trim back so the tops of all three parts line up fairly closely. If you don't then the pads meet the rim at odd angles from being displaced. I think that may be what Operator is referring to in his special way.
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Old 09-28-08, 07:23 PM   #15
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Thanks for the confirmation that you're a noob. Next please. And I've quoted the message so you can't deny it later.

First off, how bout you getting the hell off my case!!...Jerk!



My first response was directed at the OP,...Not You!!


...So's how bout you learning some simple forum etiquette instead of mindlessly stepping on someone.


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Old 09-28-08, 07:28 PM   #16
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I've found there are flats on most anchor-bolts on sidepull-brakes (Campy, Modolo, etc). And a 13mm or 14mm cone-wrench fits these - so one can easily center the calipers over the rims after tightening the bolt. Park Tool actually makes a special wrench for this, but cone-wrenches work just fine. No need to throw away good money on a duplicate tool. Unless you're a collector.
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Old 09-28-08, 07:28 PM   #17
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Like everyone said- bad idea. But it works if you tighten the QR and then hold the brake as you flip the release closed.
Ya, that is essentially what I do, plus ya gotta make sure to initially adjust the calipers to a centered wheel and make sure the axle is seated in the dropout, etc, etc.
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Old 09-28-08, 07:31 PM   #18
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...what Operator is referring to in his special way.


WR, don't let the O-man get you down. BTW, I've always considered the "thumbs up" to indicate approval...
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Old 09-28-08, 08:16 PM   #19
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WR, don't let the O-man get you down. BTW, I've always considered the "thumbs up" to indicate approval...


Well........I guess I should calm down.


I'm not upset with anyone (really)
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Old 09-28-08, 08:21 PM   #20
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Every time I remove the front wheel and reinstall it, it seems like I have to readjust the brake trim screw to recenter the the pads relative to the rim. I would expect that since the skewer is just clamping the fork to the hub which should change from side to side, the rim would reinstall in the exact same position relative to the brake. The other possibility is that the hub is not seating in the fork dropouts in the same position so that wheel is at a slight angle relative to the forks. For that reason I always press down on the front of the bike before tightening the skewer.

This is the case with both of my bikes. Is there something that I'm doing wrong when installing the wheel or is this normal?
Different thread, very similar problem, exact same solution:

Disc brake adjustment
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Old 09-28-08, 09:17 PM   #21
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Are you sure you are putting the wheel back in the same way it came out? If you inadvertenly flip the wheel and it's off dish then it *will* cause the pads to become non-centered (assuming they were centered to begin with).
Now I learn something !
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Old 09-29-08, 04:18 AM   #22
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This is the case with both of my bikes. Is there something that I'm doing wrong when installing the wheel or is this normal?
Since this seems to be happening frequently, you're probably doing something wrong.

My guess is that you're flipping your bike frame over onto it's handlebrs when you replace your front wheel. When you do this it's comon not to get the axle completely bottomed in both dropouts. Here's the easy fix:
1. Flip your bik back over onto it's own wheels.
2. Flip your quick release lever loose.
3. While pushing down on your handlebar stem, retighten the QR. - Done.
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Old 09-29-08, 11:07 AM   #23
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Thanks everyone. I did some experimenting and it seems that it must be a function of either hitting the caliper inadvertently or operating the release lever moves them slightly. I have Campy brifters with Tektro brakes. If I release from the brifters instead of the calipers and am very careful not to touch the caliper, the rim to brake clearance is very repeatable on reinstallation.
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