Results 1 to 11 of 11
  1. #1
    mtbr member
    Reputation:
    Join Date
    Apr 2007
    Posts
    124

    stripped disc brake caliper mounting hole....

    went to tighten down my caliper bolt on my almost brand new Rockshox Dart 1 today and it wouldn't torque down to spec. I pulled the bolt and wouldn't you know it I had pulled a few threads I ran a tap through and cleaned it up but was not comfortable torquing it down. I ended up putting a thinner washer on the bolt so it could grab more threads, some liquid thread lock, then hand tightened it. Seems to be ok, I didn't push it though.

    I know I'll have to service those brakes some day, so I have decided to fix it sooned than later.... I have come up with 2 ideas:

    1. Helicoils - for those who don't know these are saviors in the automotive world. You basically drillout the stripped hole, retap, then thread a steel coil insert into the hole, which creates new thread to the original diameter. These works really well with aluminum even if you didn't start with a stripped hole.

    2. Studs - A stud could be installed and locktighted in place, then a locking nut threaded on to hold the caliper. As long as the torque is correct, and the threads can hold the pressure it would work fairly well.

    Any other ideas? I think I may call Forge (the bike builder) and ask them, but I know its my word against theirs, and from personal experience stripped threads are usually guilty till proven innocent. I doubt Rockshox would do anything either.

    I know its a cheap fork, but I just got the bike so I am not looking to spend any $$ right now. I don't think you can purchase the Dart 1 retail anyways.

    Thanks!

  2. #2
    mtbr member
    Reputation:
    Join Date
    Apr 2007
    Posts
    124
    Did more searching and found this was an issue with Manitou forks for alot of people....Looks like Helicoil is the answer....

    Still welcoming advice, Thanks!

  3. #3
    Your bike is incorrigible
    Reputation: Guyechka's Avatar
    Join Date
    Jul 2005
    Posts
    3,122
    To put things in perspective, I did the same thing to my Manitou Black Elite about two years ago. The bottom half is stripped out so that it won't torque down very much at all. This in on my XC hardtail with BB7s. I figure I ride the thing about 80% of the time, so it gets a lot action. So far I have been lucky just using some red loctite and torquing it down as far as it will go without simply doing more damage. For as much riding as it has seen, it has never come loose--not once. I have loosened it to realign the caliper on several occasions, and the original loctite is still holding strong. Now this may be the cheapie fix, and who knows, I might just rip the whole caliper off at some point (no big deal since I got the fork for less than $200).

    I have been thinking of getting some plumber's thread lock and using it in combination with the loctite, just to fill the little gap left by the stripping. I think going with a helicoil is a very touchy option with magnesium lowers, since you could very well end up stripping it as well. Then you'd have a monster sized hole. I'd say try the loctite first. Put some threadlock on there as the next option. And be very careful when you tighten down.

  4. #4
    mtbr member
    Reputation: Hardtails Are Better's Avatar
    Join Date
    May 2005
    Posts
    6,298
    I'm with Guycheka. Helicoil in magnesium sounds scary. Seeing as how you havn't really badly stripped it out, I'd use some red loctite, and hope for the best. Failing that, helicoil is your best option, but I'd try loctite first.

  5. #5
    MTB B'dos
    Reputation: LyNx's Avatar
    Join Date
    Oct 2004
    Posts
    17,229
    Was going to straight up say "yeh helicoil", but then saw Guyecka's reply and remembered it's not alu you'd be doing it too. I'm not sure what magnesium is like compared to alu, so if you do it I'b be very careful. I know I had to do it to my actual brake caliper and it's alu and no problems what so ever. Maybe do what I did as a stop gap and get a longer bolt and put a nut on the end - not sure how the post mount forks are, if the holes go right through or not so don't kow if this'd work.
    One day your life will flash before your eyes, will it be worth watching??
    MTB Barbados
    My MTB vids

  6. #6
    mtbr member
    Reputation:
    Join Date
    Apr 2007
    Posts
    124
    ok... thanks for the advice.

    I am able to tighten it down pretty good, and I used locktite on it.

    I need to contact Forge and talk to them about the conflict in paperwork. Hayes says 100 in/lbs, Rockshox 80 in/lbs. Guess which on I was reading when adjusting the brakes.....and what I torqued it to.....

  7. #7
    Flyin Canine
    Reputation: shanedawg's Avatar
    Join Date
    Jan 2004
    Posts
    2,281
    This is why it pisses me off that all of the fork makers are moving towards post mount brakes. What they hell was wrong with the IS standard? If you stripped the threads there all you had to do was go buy another $15 caliper mount.

  8. #8
    Your bike is incorrigible
    Reputation: Guyechka's Avatar
    Join Date
    Jul 2005
    Posts
    3,122
    Quote Originally Posted by shanedawg
    This is why it pisses me off that all of the fork makers are moving towards post mount brakes. What they hell was wrong with the IS standard? If you stripped the threads there all you had to do was go buy another $15 caliper mount.
    My sentiments exactly. I was reading about this a few weeks ago, and there was a reason that escapes me now. Must not have been a very good reason. Personally, I think they should stick with IS and make Avid's elliptical washer system stock on all caliper mounts. Screw PM and screw stupid little spacers (now they have big spacers that go between the rotor and hub! )

  9. #9
    Do It Yourself
    Reputation: Homebrew's Avatar
    Join Date
    Jan 2004
    Posts
    5,722
    You should have a good amount of usable threads past where you stripped it out. Use a longer bolt that isn't tapered at the end to maximize the threads and use plenty of loctite. I did the same thing on my old Minute. It pulled like cheese well below the stated torque spec. They really should use longer bolts with square ends for PM and they should come with the fork.
    Long Live Long Rides

  10. #10
    mtbr member
    Reputation:
    Join Date
    May 2007
    Posts
    117
    Helicoils and magnesium are not a problem, it's used all the time on older Porsche magnesium engine blocks when the head studs get pulled out of the crank case. And plumbers PTFE tape would be a bad choice for loose threads, it's not used to lock the threads. It would be better to fill the hole half way with JB weld and re-tap starting from the other side, using the good threads for a starter and alignment.
    -Scott

  11. #11
    LBS Manager
    Reputation: Johnny Hair Boy's Avatar
    Join Date
    Jul 2004
    Posts
    1,890
    This is why tabs are so much beter than post mount. It is much beter to strip a cheap ass bracket or caliper than your fork lowers. It seems that more companies are going post mount and that realy sucks. I hope they start doing some sort of replacable theaded insert. That said I have never know anyone personaly to ever strip their fork lowers but this thread has shown that it is posible.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •