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I recently took off the front wheel off of my mountain bike, and have been having considerably difficulty getting the front wheel on the right spot such that the wheel doesn't rub against the brake when I'm riding. I know there is clearance possible, because if I pull the quick release on my wheel and turn the wheel, it spins just fine. What can I do to align the brake properly?

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More than 50% of the time I take off a wheel, I have this problem. I would be VERY interested to know why is this happening. Then how to prevent it, instead of re-adjusting a disc brake after every tube change / tube repair! – Vorac Oct 2 '12 at 6:55
    
As it happens intermittently, have you checked for a broken axle? – mattnz Oct 2 '12 at 22:23
    
@mattnz: I doubt it, it's more likely just that I can't line everything up right. I can get it to line up better sometimes, but when I started noticing this problem, I was well down the road, so... Still, thanks for the possibility! – PearsonArtPhoto Oct 3 '12 at 1:15

Tip of the day for how to adjust brakes so they dont rub when tightened:

Use shims on either side of the disk!

Here's how to do it:

  1. Get a beer can and cut a strip about an inch wide and 6 inches long (careful when using this, it's sharp)
  2. Take the wheel off the bike, loosen up the hex cap bolts on top of the calliper, not the wheel, adaptor, etc
  3. Put the shim over disk, in the position where the calliper will float over it, put the wheel back in so the shim is now jammed up into the loosened calliper and do up your quick release nice and tight
  4. Put the brake on a little (to centre the calliper) and tighten up the calliper bolts.
  5. Remove the shim (you may have to remove the wheel) and you should have a really properly aligned brake (either cable or hydraulic).

Make sure your beer can strip is really clean (use soapy water and properly rinse) so you don't contaminate the pads or disk.

I've got Avid Juicy brakes and I had huge problems with getting them properly aligned so they didn't make little squealing sounds whenever I was riding (they never really rubbed) and this made it so much more pleasant!

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Assuming you mean that the disk caliper pads are rubbing on the rotor when the lever is not being used/squeezed:

1) The fixed/non-moving pad/side in the caliper on my brakes are adjusted with an allen key from that outer side of the caliper. If it has been a while this bolt could require some effort to get moving. On my brakes there is a detent such that I back off the bolt one click at a time and see how the clearance is.

2) The moving pad/side in the caliper is adjusted by cable tension in the usual way, i.e. with the barrel adjuster at the lever or the pinch bolt at the caliper.

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@Vorac - are you saying you make the adjustment and it is rubbing again next time? Or sometimes it rubs and sometimes it doesn't after wheel removal/replacement? If the former, you might have a rotor that is warping – Arbalest Oct 2 '12 at 20:46
    
@David Sopko - when the skewer is locked down, the fork drop-out is pinched between the bearing/cone and the skewer nuts. Backing off a bit would mean that the dropout is not being pinched as tightly. If the skewer is loosened enough to have any effect on the position of the caliper the wheel will almost certainly be too loose to ride. – Arbalest Oct 2 '12 at 20:50
    
@original poster and everyone else - the first time I had this problem I didn't have a ready access to an allen key to make the adjustment. What I did for the short term was to make a very thin washer/shim by cutting a circle out of a clear plastic package (that some other bike part came in). I put it over the axle between the drop-out and bearing on the side that was rubbing. That moves the whole wheel over the width of the shim. But, this is just a short-term fix until you make the proper adjustment. – Arbalest Oct 2 '12 at 21:04

@Arbalest has the correct answer for one specific problem with brakes with just one cylinder, If that is not it, the best way would be to reset the caliper alignment. I am not expert, theres heaps of information on how to do it - the owners manual is a good start - it's not hard, but a novice may need a couple of goes at it to get it spot on.

Essentially, loosen the bolts holding the caliper enough so it moves, but is not loose. Pump the brakes gently a couple of times with the wheel spinning (in normal direction). Then while applying the brakes "firmly but not hard" (i.e. enough to hold the caliper in place), slowly tighten the bolts, alternating between them 1/2 turn at a time (so it tightens evenly on each side).

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I've had this problem with more than one bike, and risk factors for that are:

  • Quick-release hubs (as opposed to 20 mm, thru-axle);
  • Long travel forks;
  • "Light" or otherwise delicate forks (even good quality ones);
  • Mechanical brakes (one pad non-moving);
  • Large-diameter (8 inch) disks.

The problem is that, due to the very tight distance between the disk and the pads, a minimal amount of "shape changing" creates rub and noise. This shape changing might occur between opening and closing the quick release, or because of more aggressive twisting forces while cornering on difficult terrain.

Usually, a little rubbing is not a real problem, but much more of a nuisance, and even very small rubs can cause an unpleasant noise.

One possible solution, and one that works for me when I'm in an "I need silence" mood, is to catch the front wheel of the bike in a corner, or even against a wall or a tree or a fence, and TWIST THE HANDLEBARS. If you do this gently, you'll notice that the fork twists (a tiny bit of course) enough to make the disk reposition itself inside the caliper, also showing the direction you should apply a greater force to reposition the disk/caliper "permanently", and this is enough to solve the problem, but only if the rubbing is minimal (otherwise it is necessary to properly adjust the brake).

Of course I am not suggesting to twist anything in a way that would cause damage, but I think some setups are so prone to misalignments that the same poison should cure the disease, and that's it.

Also, of course this problem has a WAY smaller chance to happen with non-quick-release. 20mm thru-axle hubs/forks.

Hope this helps!

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