Adjusting disk brakes after taking off the wheel

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.

@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).

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!

This is a recurring problem with QR (as opposed to 12mm, 20mm through-axles).

Turn the bike upside down so gravity helps you with re-seating the wheeel.

Attempt to install the wheel (push and rock it well into the dropout); then engage the breaks a couple of times to reset the pistons; rotate the wheel; hope for no rub. Do this multiple times, as it is far faster and easier than other techniques.

If it fails, refer to the other answers. Your disc could be wrapped, your caliper could be off-center, your pads could be mis-aligned, mis-worn, mis-whatever. Good luck and happy riding!

When using QR axles (my preference FWIW) with disc brakes, it's important to make sure the wheel gets seated in the fork ends exactly the same every time, and that it doesn't shift in riding. QR axles can cause tiny differences in wheel position, which never mattered with rim brakes, but which can cause hassles with disc brakes rubbing.

My method:

--mark your axles and install them with the same rotation every time. This is easy with my dynamo hub because I rotate the electrical plug straight up every time. For other hubs, I mark one flat of the axle lock nuts and install that flat straight up every time.

--cram the wheel completely into the fork ends while tightening the QR. This ensures a consistent position and reduces chances of the wheel shifting from a bump. I tighten my QR from the riding position, while leaning my full weight into the handlebars with my waist, pressing the wheel fully up into the fork ends.

--use a good QR. Any internal cam Shimano QR is fine or most any QR with INTERNAL CAM. The QR's with the external cams go in the trash. In my experience they are marginal anyway and right out for a disk brake world.

After doing the above, I use the typical business card method to adjust the brake caliper position. There is no need or benefit to shimming the rotor unless you cannot adjust the caliper enough without the shim, or unless you want to be able to swap different wheels, then shimming the rotor can make sense

With these practices I have no problems anymore with disc brake clearance shifting when changing a wheel, and I even run a 203mm front rotor and a cable caliper with single-piston design on my cargo bike with no problems. I'm also slightly picky able my lever slack and engagement.