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While adjusting disc brakes, I often find that the caliper body slightly slides sideways when tightening the mounting screws. It is sometimes due to sticky washers, but I also encounter this issue with new out-of-the-box brake parts.

Is there a trick to prevent this and ensure the caliper body stays still when I tighten the screws ?

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    Are you holding the pads hard against the disc by pressing on the brake lever, while tightening the screws?
    – quilkin
    Commented Jan 27 at 22:24
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    Always had this problem. More so with older used calipers. Cleaning washers and screws helps but does not eliminate the problem. Just get used to it. I tend to hold the caliper with my hand or jam it in place with a brake lever to prevent it from sliding when tightening the bolts. Commented Jan 27 at 22:30
  • I agree, this is always fiddly. I often need to tighten and release the screws 2-3 times before I get it right. The Hayes Dominion brakes have little grub screws to avoid exactly that, would be nice to see that adapted also into more affordable brakes. Commented Jan 28 at 10:20

4 Answers 4

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The technique I have had the most luck with is to gradually tighten the mounting bolts. Tighten the top bolt until it just starts to hit the caliper. Do the same to the bottom bolt. Keep alternating between the screws while gradually increasing the torque on the bolts until you reach the specified value. To keep the caliper centered in the rotor I install a shim made of paper, one on each side. Use a rubber band to squeeze the lever toward the grip to clamp the pads to the rotor while you tighten the bolts.

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  • Thanks for the answer! That's what I do as well. I was wondering if there were other tricks in the book. Commented Jan 29 at 15:53
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I struggled with this at first.

It helped to have everything clean, and to have good threads that engaged smoothly. I also used loctite which lubricated the threads on the way in and eliminated any "catching"

You should have washers in the stackup too - make sure they're the correct way around and don't have burrs or dings on them.

As for technique, use a hand or clamp on the brake lever to lock up the caliper on the rotor as you tighten down the bolts. When they're firm, alternate between the bolts rather than clamping one hard and then doing the other.

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There are two things you can do to significantly mitigate this issue.

The first is to engage the brake, as strongly as (safely) possible, while tightening the caliper mount bolts. Assuming you properly reset the pads/pistons (which you should be doing anyway when realigning disc brakes), this will ensure that the caliper is properly centered before you start tightening, and keeping the brakes engaged while tightening will provide quite a bit of resistance to the caliper moving as the bolts are tightened.

The second is to handle tightening the bolts properly. Start by getting things to the point that they’re actually holding the mount in place, then alternate between the bolts tightening about a quarter or half turn at a time. This makes it far less likely that you will have things shift, but it also helps ensure even loading of the individual bolts, which is really important for reliability reasons and will also make it far easier to loosen them again in the future. You should be handling tightening of any set of bolts that need more than about 1-2 N m of torque this way. For two bolts just alternate, for three work in a circle, for four in a ‘bowtie’ pattern, for five or more in a star pattern.

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Whenever I fine adjust disc brake calipers (especially under circumstances where simply engaging the brake does not center the caliper), I do these steps:

Assuming the bolts are currently tightened after the aformentioned method:

  1. back off one bolt to what I feel is 75% of its full tightening/torque
  2. back off the other completely loose.
  3. push/pull the caliper on the side of the loose bolt until that side of its brake pad is center.
  4. tighten the loose bolt to 50%, tighten the 75% bolt to 100%, and tighten the 50% bolt to 75%.
  5. completely loosen the 100% bolt, and do #3 on that side.
  6. tighten loose bolt to 75%, then both to full torque.

It sounds complicated on paper but its somewhat intuitive when you get the feel for it. Plus, the caliper doesn't creep off-center in my experience with this method.

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