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Discussion Starter · #1 ·
I had a problem with the rotor moving toward the wheel during the final tightening with the torque wrench. The front bolt (rear caliper) is fairly easy to hold in place to help out, but the back bolt had no room for my fingers and no leverage point for bracing.

Finally found what I think will be a good method to hold it in place, down in the picture. I used some mule tape, but any easy to grab cordage should work. More and more tension is needed as the bolt gets tightened.

 

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West Chester, PA
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You could also be experiencing an out of spec post mount. You could run it by your LBS as see if they can face the PM for you 馃憤
Try sanding the mounts before paying a shop to check and face them. Don't go crazy. Just CAREFULLY take the paint off the tops by placing sandpaper over your finger and twisting it back and forth. No files!
 

Disgruntled Peccary
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Best method I've found is to alternate between the bolts as I tighten them.

Of course, then there are the Hayes Dominion calipers which have little grub screws that let you dial in the caliper position before you tighten the bolts and hold it in place when you do tighten them. Those are ingenious.
They're very easy to use, as long as you tighten the top bolt first no creep. Seconds to center the caliper.
 

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Best method I've found is to alternate between the bolts as I tighten them.

Of course, then there are the Hayes Dominion calipers which have little grub screws that let you dial in the caliper position before you tighten the bolts and hold it in place when you do tighten them. Those are ingenious.
IMO, all calipers should be made like the dominions with the caliper adjustment screws, especially with the tighter rotor/pad tolerances we鈥檙e seeing these days with rotors getting thicker.
 

Elitest thrill junkie
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Caliper alignment tool or business cards work well.
Not for this problem. The problem is the caliper is indexed to the mount, so no matter how you position it, it will go back to the original position as you tighten, because that鈥檚 how it 鈥渇its鈥, like the piece of a puzzle, unless you have a method to force it not to, like the OP posted.
 
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Elitest thrill junkie
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Try having the fork tabs faced. This can help completely eliminate that issue where the caliper shifts as you tighten. Another trick is to alternate between bolts and 'micro-tighten' each one. If that is even a word?

That would only be temporary, because you just create a new indexed location when you tighten for the first time. As you tighten the bolts, they will leave impressions on the material and they will seek out that spot on any subsequent tightening. The issue will re-appear any time you do something like change rotors or possibly even brake pads and you are trying to center the caliper around the rotor. The problem is indexing and this is an inherent issue with this type of caliper mount. Mind you, it's usually not a huge issue for most people, but it definitely happens. The old IS mount using the shims was a better setup, since you could shim it to not rub, but this also required a perfectly perpendicular adapter/mount. This is where facing was important (and hard for manufacturers to get perfect every time). The brake calipers with the set-screws are a smart idea.
 
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That would only be temporary, because you just create a new indexed location when you tighten for the first time. As you tighten the bolts, they will leave impressions on the material and they will seek out that spot on any subsequent tightening. The issue will re-appear any time you do something like change rotors or possibly even brake pads and you are trying to center the caliper around the rotor. The problem is indexing and this is an inherent issue with this type of caliper mount. Mind you, it's usually not a huge issue for most people, but it definitely happens. The old IS mount using the shims was a better setup, since you could shim it to not rub, but this also required a perfectly perpendicular adapter/mount. This is where facing was important (and hard for manufacturers to get perfect every time). The brake calipers with the set-screws are a smart idea.
The caliper sliding will happen on brand new caliper/fork installs. Fox forks are the worst. Rockshock, Helm, dvo, etc.. all do some bit of machining on the post mount. Fox just paints over them.

I've run into this issue enough times that the first thing I do on a bike build is clamp the fork in the stand and face the tabs. It will save me time in the long run when aligning the front caliper.
 
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