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Corroded allen bolt - front fork brakes

GavHGavH Posts: 933
edited November 2010 in Workshop
I went to remove the front brakes from my summer bike today to give them a thorough clean and was shocked to discover that the bolt was corroded so badly that I can't get an allen key to fit it.

Any tips or is this a trip to the LBS to drill it out? :(


  • redveeredvee Posts: 11,921
    I had this with a bike I've acquired and tried the Torx bit in the allen socket trick, it worked till I tried to turn it then broke :shock: so I had an allen bolt with no hope of undoing and the calliper still stuck in the forks. I had to dismantle the calliper from the front of the forks. Bought a cheap sacrificial screwdriver to hammer out the torx bit and will have to drill the allen bolt out when the 'new' callipers arrive later this week.
    Best left to the LBS but be aware that there maybe additional costs as above.
    I've added a signature to prove it is still possible.
  • GavHGavH Posts: 933
    Thanks. Just been in to one of my 2 LBS and the guy suggested I'd have to SAW the brake caliper off :shock: !

    Think I'll PM the other LBS on Facebook and ask them instead!

    Alternately, I wonder if glueing an allen key in place might just give enough purchse to unscrew it. I assume though that if the corrosion is such that the hex shape has all but gone, the thing isn't necessarily going to want to come out all too easily? :?
  • sungodsungod Posts: 14,375
    can't you use a bolt extractor?

    i used one to get a stem bolt out after discovering the hard way that my torque wrench was faulty

    if the bolt is corroded give it all good soak for a couple of days in acf-50 or penetrating oil before trying to extract it

    you can buy them one-off at a tool shop, or get a kit of sizes like... ... =ukfroogle

    fiddly bit is drilling the pilot hole, but if you've still got the bolt head it should help get it central
    my bike - faster than god's and twice as shiny
  • Monty DogMonty Dog Posts: 20,614
    Are you sure it's not just muck preventing you getting the Allen key in place? Try tapping an Allen key into the head to dislodge any rust/muck etc, remove key and blow-out any crud. Spray some PlusGas/WD40/GT85 in too to help get it moving.
    Make mine an Italian, with Campagnolo on the side..
  • GavHGavH Posts: 933

    Definately NOT just excess crud, the whole fat end of the bolt was just rust. I ended up wrapping an allen key with a bit of tape, just enough to wedge it in. Angling the key just a touch enabled me to maintain some pressure on the bolt whilst I simply rotated the entire caliper on the other side! Eveentually, the caliper screwed off; in essence the reverse of what I would have ordinarily done.

    Now, where do I source a replacement? It is pretty much identical to the bolt on the 'Recessed Mounting' example, left hand side picture of two, about 2/3 down on Sheldon's site:
  • redveeredvee Posts: 11,921
    GavH wrote:
    Now, where do I source a replacement?

    SJSC or any shimano service centre.
    I've added a signature to prove it is still possible.
  • Monty DogMonty Dog Posts: 20,614
    All brake bolts are standard - just make sure the replacement is stainless steel, not chrome plated steel
    Make mine an Italian, with Campagnolo on the side..
  • You can also try sticking a piece of insulation tape over the head of the new bolt to cover it up when you've fitted it. That way the road pooh doesn't get to it. Check the tape occasionally - cheap stuff sometimes gets manky and peels off.

    I know it's a case of stable doors and all that, but next time....
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