I drive a 2003 Ford Ranger with front disc brakes. About two years ago I replaced the rotors and pads and am sure I used a thread lock during assembly (and torqued to spec).

The other day when I was applied the brakes on a freeway offramp I the truck behaved almost like it had a flat. When I inspected everything one caliper had a slight bit of play. So I disassembled, cleaned, and reassembled everything and the issue seems to be resolved.

During reassembly I used blue thread lock, but am second guessing if that's the right option. I've always used blue for anything I'll disassemble and red for anything permanent--but given brakes generate quite a bit of heat I'm wondering if those aren't the right option.

What variety of thread lock is best for ensuring the caliper mounting bolts stay put and correctly torqued? I'm looking at the bolts that mount the bracket to the knuckle, as well as the caliper to the bracket.

  • 2
    I've done brakes on a dozen or more cars and never used any sort of thread locker. I've never had an issue with bolts coming loose. It's usually a struggle to get them loosened on purpose. Just set the bolts to the proper torque spec and you should be good to go.
    – FreeMan
    Commented Sep 1, 2022 at 18:26
  • Thanks! The issue I was trying to resolve still isn't fixed, so I was wrong in diagnosing it in the first place. The bolts definitely weren't loose when I disassembled things, I was able to get them out with a breaker but almost brought in a floor jack to cheat then off. They're back together with a dab of the blue stuff and torqued to 90 ft/lb so I'm confident they'll start put--and will take it to a pro unless something more obvious jumps out at me with a little more poking around
    – STW
    Commented Sep 1, 2022 at 20:50
  • Maybe ask a question focused on the "bit of play" in the caliper issue. I'm sure you'll get some good input.
    – FreeMan
    Commented Sep 2, 2022 at 11:29

1 Answer 1


Generally threadlocker is not called for on caliper bracket bolts as the proper torque will hold them securely. But if you want to use it, I would not use anything but "blue".

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