Bicycle Mechanics - chainring bolt issue - broke off

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nayr497
10-09-08, 05:28 PM
I was doing a general check over on one of my bicycles today. Using a star hex wrench I tested the chainring bolts. One was loose. I tightened it, then went to tighten the next one. It was a little loose, turned a bit...then it turned free. The front of the bolt threaded into the rear and both fell out on the ground, broken.

My question: should I be going after steel bolts to replace them? I'm wondering if I got cheap bolts or what. I've really cranked down chainring bolts before and never had this happen.

Some searching has revealed that there are aluminum and steel chainring bolts, as well as some that use a hex wrench on both sides, not hex on front side, those funny two teeth bolt wrenches on the back. Those seem like a nice upgrade.

DETAILS: bolt around 6 months old, single-stack (as it is a fixed gear), made by Pyramid (I think a BMX company, which is all the LBS had), and the bolts were greased before tightening them at original installation.


Ideas??

Ex Pres
10-09-08, 05:39 PM
Bolts are cheap: buck, buck and a half each? Just buy another and forget about it.

And they don't have to be torqued that hard. That's why that little 2-pronged wrench is enough.
nayr497
10-09-08, 06:01 PM
Thanks for the reply, Bob.

The reason I tried to tighten them down was because a few months back I was riding down a hill when suddenly I heard a loud crunch and somehow stopped quickly and wasn't thrown. I looked down to see my chainring folded in half.

From what I gathered via this forum my chainring bolts were not tight enough, my chainring moved laterally, my chain skipped some, recaught and folded the ring. Thus, I thought tight chainring bolts were crucial and why I was tightening them down.

I'm thinking when riding fixed more stress is put on the crankset/chainring with backpedaling. Maybe, maybe not. But seems like the chainring bolts would be under more stress on a fixed gear than a multi-speed bike with a derailleur.

operator
10-09-08, 06:54 PM
And they don't have to be torqued that hard.

Wrong.

They have to be torqued properly, which is _not_ what you just said. The 6/5mm chainring bolts are the best thing that's happened to them since sliced bread.

The two pronged pieces of crap is amazing when you have to get one off that is semi-seized or seized. If you have the option, buy those.