Bicycle Mechanics - Front centerpull brake removal - BOLT STRIPPED!

I am needing some help. The front brake on my 1983 Miyata Two Ten is a Dia Compe centerpull. I need to loosen the fixing bolt which passes through the fork, but the allen threads are all hootered up evidently by some past jamoke trying to loosen a metric allen nut with the wrong size allen, or some such antics. I have entertained pounding a slotted screwdriver into the nut and backing it out that way, in which case I'd need to procure a replacement. Anybody know if this will work, and if so what is the size of this allen nut? Seems a M4 but I don't want to make any assumptions. Could be something else.

Also - I'm just trying to mount a front fender. I made a ghetto-bracket that inserted up into the head tube from underneath with just enough friction to hold it, but long term I want to be mounted properly. Any other ideas on mounting a wood fender? :twitchy:

crashmo: If the socket is stripped out you will need a replacement regardless of how you remove it, so your goal should be to do no harm to the bike. Instead of pounding a screwdriver into it, which might expand it out into the hole, or worse, distort the fork, why not use a Dremel or a narrow hacksaw blade to make a slot for the screwdriver? If that doesn't work an easy-out might do the trick. Once you get the nut out you can figure out what thread you need for a replacement. I would imagine that any good LBS should be able to help you out.

crashmo: If the socket is stripped out you will need a replacement regardless of how you remove it, so your goal should be to do no harm to the bike. Instead of pounding a screwdriver into it, which might expand it out into the hole, or worse, distort the fork, why not use a Dremel or a narrow hacksaw blade to make a slot for the screwdriver? If that doesn't work an easy-out might do the trick. Once you get the nut out you can figure out what thread you need for a replacement. I would imagine that any good LBS should be able to help you out.

Agree with the above, emphasis added. The best way I've found to remove these stripped Allen bolts is to drill deeper into them to allow an easy out to gain purchase and unscrew them with that. A pretreatment with penetrating oil (I like a product called "Blaster PB," available at Home depot. It works better than anything else I've tried.

Good stuff, guys. I was looking at it this evening and it seems I could use a cut-off wheel on my dremel right through the hole in the bottom of the fork, and then just replace the bolt & nut.... the crappy part is that the nut is dead flush with the fork, no protrusion whatsoever.

What exactly is an easy out? I've never used one o' those. Is it one of those helical reverse threaded thingies? If you own one of those, how often do you use it?

Good stuff, guys. I was looking at it this evening and it seems I could use a cut-off wheel on my dremel right through the hole in the bottom of the fork, and then just replace the bolt & nut.... the crappy part is that the nut is dead flush with the fork, no protrusion whatsoever.

What exactly is an easy out? I've never used one o' those. Is it one of those helical reverse threaded thingies? If you own one of those, how often do you use it?

An "easy out" is also called a "screw extractor." Some have reversed helical threads...but all work on the principle that they bite into hole drilled onto a right threaded bold so you can extract it by turning in counterclockwise. I don't use them a lot, but when I have used them they work great.

Nick

FWIW, I used a screw extractor to remove a stripped philips-head screw out of the bottom of a 1999 iMac G3 so I could get to the insides to get a look at why it wouldn't show any video. I got the iMac free. For anyone who's wondering, the video cable had come loose.

Sorry for the thread derailment.

Sorry for the thread derailment.

No problem. Did I tell you about my cat?

You can weld a nut on the top and then use a wrench.

I think cashmo is on the right track if he can reach the bolt from the bottom there should be no issue cutting it. As for the bolt replacement you can find a bolt replacement brake cheap at just about any bike shop. Dia-comp made there basic center pull for over ten years with no real changes and sold about a million of them.