Sheared a pinch bolt! - 600RR.net
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post #1 of 2 (permalink) Old 08-31-2009, 09:36 AM Thread Starter
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Sheared a pinch bolt!

Sorry - this is going to be long-winded, but here goes:

About a month ago I got new tires mounted and balanced at Cycle Gear. Afterward I noticed a terrible headshake from about 40 mph up. I checked the wheel, and sure enough they'd installed 2.5 oz of balance weights right beside the .5 oz that was already on the front wheel from the factory. I've been busy, so didn't have a chance to bring it back for rebalancing but kept riding it with the shake.

This weekend I took it off, brought it back to CG, and asked them to rebalance it. This time the guy said "Yeah, there was WAY too much weight on there - it only needed 1/4 oz."

So I went home to install it. I never even reached the spec'd 16 ft-lbs on the farthest left pinch bolt. I had a steady, smooth turn while the bolt stretched, then it sheared off inside the fork. All I can figure is that the vibration fatigued the bolt just shy of breaking, then I took care of the rest.

I managed to slot the end of the bolt with a Dremel and turn it all the way out of the back of the fork with a flathead (thank Honda it was threaded all the way through), then bought a new set of pinch bolts. I installed all four, torqued them down, then rode a while. When I got back home I retorqued to check, and got about another half-turn out of the far left before the torque wrench clicked. So my guess is those threads are (pardon the pun) screwed.

Has anyone had something similar to this happen? Not necessarily the same circumstances, but just the end result of mangled threads on the pinch holes? My plan is to get a 1/2" longer bolt to go through and past the hole, then Loctite a backing nut on there behind the fork as a failsafe. Does anyone see a problem with that I'm overlooking?
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post #2 of 2 (permalink) Old 08-31-2009, 11:53 PM
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Nice job on the fix. I don't know if I would worry about it. Lugnuts on a car will lose some of their torque but not because of bad threads. More just getting all the different directions of forces will settle it in. Then you have to torque them again.

I would torque it the second time (like you did) then take it for a ride again. If it looses its torque again, then get the longer bolt with a nut on the back. Also, they make nuts called Nylock. Just a small nylon piece in it to keep it from backing out. Maybe just something easier than using loctite.

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