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February 11, 2007

How to undo stripped (disc brake rotor) bolts

Filed under: Howtos / tips / tricks — mtbguru @ 6:56 pm

Now for something completely different: last weekend I needed to perform a simple bike maintenance task: replace the worn out front rotor of the disc brake on my mountain bike. I’d done this before, and it’s one of the easiest things to do: take out wheel, undo the six bolts that keep the rotor on the hub, put new rotor on.

It becomes less straightforward however when you manage to strip one or more of the bolt heads. For obvious reasons, these bolts which go in the threads of the hub are treated with (blue) Loctite; they do tend to get stuck pretty well in there. The bolt heads are of the Torx type and I managed to undo all but one of them with the wimpy Torx tool I was using. Unfortunately, the last one turned out to be really stubborn, and my screwing around with it (no pun intended) resulted in this:

stripped torx head

Visions of taking drastic measures such as throwing a blow torch at the problem, buying an impact wrench or having to accept defeat and go to the shop arose… luckily however I needn’t fear, as there is a much simpler and quite efficient trick, which I’d like to share in this post.

I remembered to have read somewhere that a simple trick was to cut a slot in the bolt head and then use a regular screwdriver to undo the bolt. Time to try this out so I took off and got this mini-hacksaw ($6 in ACE Hardware):

hacksawhacksaw 2

It worked like a charm. The bolt material turned out to be relatively soft, and the finer blade that came with the saw was just right.

slotbolt undo

When the slot was deep enough so that I could apply some decent force with the regular screwdriver, the bolt went off fairly easily.

boltsnew rotor

Time then for new bolts and a new rotor. The blue Loctite was conveniently already applied on the bolts that came with the new rotor.

This is how the old rotor looked like:

old rotor

It was getting worn out significantly, notice the thinned down center area (where the pads grab). With the new rotor, braking power immediately felt much higher.

Note to myself: next time use a proper Torx tool to undo the bolts:

Torx tools
(Wimpy and Beefy tool)

2 Responses to “How to undo stripped (disc brake rotor) bolts”

  1. Paul Says:

    Just had to swap rotors between two wheels – ended up having to grind a screwdriver slot into 11 out of the 12 rotor bolts using a 5inch metal grinding disk. After that, I compressed the threads with a few taps of a screwdriver and hammer. Then I stood each wheel up and used the hammer and screwdriver to tap the bolts around anti-clockwise to loosen. Worked a treat.

  2. Brad Says:

    The hacksaw trick did the job for me, saved the day.

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