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I recently purchased an old road bike and I am trying to restore it. One of the main problem was a rubbish brake installation by the previous owner.

I tried to remove the nut and the bolt that hold the rear brake caliper, but it seems like the bolt got its threads stripped. I can turn the nut infinite times.

What I tried was trying to pull the bolt towards the exterior of the bike while rotating the nut so it could take a bite into the thread, but it didn't work.

What do you guys recommend? My last option was to take it to some hardware store so the cut the bolt where the washers are at.

Here are some photos:

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4 Answers 4

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On the front side, you have an okay safety buffer for cutting the pivot bolt off with a hacksaw or Dremel cut-off wheel. Cut between the stack of washers and both blocky aluminum pieces unless you can tell that only the outer one is integral with the pivot bolt. You could also use the cut-off wheel to split the nut down the middle, stop once you're most of the way so you stay clear of the frame, and then jam a stubby screwdriver or flathead bit in and twist it to break it apart.

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Safest for the frame is a nut splitter. Its a $10-$20 tool so a lot cheaper than repairing damage to the frame if other techniques suggested fails you.

If you don't want to buy a nut splitter or use a dremel/grinder, you can drill through one of the nuts flats with two or three drill holes (in line with the bolt). Support the nut on the opposite side so the impact is not taken by the frame, place a screwdriver across the holes and sharp blow with a hammer will split the nut open. (I have done this on an M14 nut my splitter was too small to fit, it was surprising how easy the nut came apart).

Another option would be drill the bolt from the nut side with a drill bit lightly larger than the outer thread diameter, being very careful to stop before hitting the frame. The washer should start to move around before the drill bit touches the frame.

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If it were me, I'd drop out the rear wheel to get more access, and protect the tyre. Then I'd use either a Dremel cutoff wheel or a small electric grinder with a cutoff wheel, and aim to cut one of

  1. Vertically/horizontally through the nylock nut on the front. The washer at the back should provide sufficient protection for the frame as you cut. Could be hard to get a large grinder in here, but a 100mm/4" disk should fit fine.
    enter image description here

  2. Second preference is to cut the rear off. I can't be sure how much of the bolt is spacer and how much is flange, so aim to cut through the bolt parallel with the washers. The washers will help keep the cutting disk away from the frame, but I'd still protect it with something like wood or cardboard.
    If you only had a hand-hacksaw then I'd cut here first, because its held out from the frame further by the stack of washers.
    enter image description here

Just take your time, avoid going all apprentice-gorilla on the tool, and when you're almost through stop sawing and try bending the part by hand.

Hopefully you have a good-sized replacement caliper ready to install. Don't be tempted to go without a brake, they're important.

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With the thread stripped there should not be much holding the nut in place so I would try drifting it out. That is, find Drift Punch (or similar object) with a diameter small enough to pass through the nut. Apply Drift to middle of bolt and tap it with a hammer. Start tapping gently and stop well before there is any danger of damaging bridge/frame if it doesn't move.

Otherwise splitting the nut is best option. There are specialised nut splitting tools for that that might be easier to use. But with a bit of care, it is also possibly to use a hacksaw or Dremel tool for the job as suggested in other answer.

Addendum - another possibility - maybe ...

One other possibility occurred after Criggie's comment ...

If there is enough play behind the nut to insert a thin prying object e.g. old flat bladed screwdriver, then sometimes it's possible to persuade what remains of a thread to work well enough to undo the nut one final time.

To do this, insert and use the pry to exert a gentle removing force on nut. Again be careful not to damage frame. Based on pictures best location for this would be the stack of washers on the opposite side of the bridge to the nut. Then while exerting the pressure with the pry try undoing the nut [0]

[0] Using a socket set will makes this two handed operation a bit easier. As will persuading a friend to join in with the fun.

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    Drifting it out sounds risky to the brake-bridge part of the frame, which normally is under a twisting or rotational force, not a sideways force. I'd prefer a nut splitter or a careful application of a dremel cutoff wheel through the nut. The shaft will not be reused I'm sure.
    – Criggie
    Feb 2, 2022 at 2:31

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