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General Category >> Technical >> Loose Bottom Bracket
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Message started by bent_eagle on Mar 2^nd, 2008, 1:55pm

Title: Loose Bottom Bracket
Post by bent_eagle on Mar 2^nd, 2008, 1:55pm

This may seem dumb to you more knowledgeable bike mechanics, but I had an interesting mechanical experience yesterday. I was about halfway through a 62 mile ride, when I noticed a new creaking sound coming from the area of my pedals/cranks/BB. It only happened when I was pedaling with a pretty good load on the chain, like when climbing a steep hill.

After watching my rings go around for a while and trying to figure out what the problem was, I noticed that the chain was drifting right and left as I rotated the cranks. I pulled over to get a better look, and I found that I could wiggle the rings and crank arms side-to-side slightly with just finger pressure. When I got home, I found that my 8mm wrench fit perfectly into the bolt in the center of the cranks, and that they were pretty loose. I tightened them down, and the wobble went right away.

It never even ocurred to me that cranks might work themselves loose, but I guess this falls under the old maintenance tip of periodically checking all bolts and nuts on your bike for tightness.

Title: Re: Loose Bottom Bracket
Post by Bud_Bent on Mar 2^nd, 2008, 2:56pm

Yep, good reminder. There are lots of things that can become loose, and that's one of them. Another, that I never would have thought of on my own, came from the Bacchetta forum. A rider had the main bolt holding his brake on come loose, and it caused a crash and much bike damage when the brake came off. I've added that to my list of stuff to check, too.

Title: Re: Loose Bottom Bracket
Post by bent_eagle on Mar 2^nd, 2008, 3:49pm

Holy crap, thanks Bud. I'll go check mine right now!

Title: Re: Loose Bottom Bracket
Post by FlyingLaZBoy on Mar 2^nd, 2008, 3:55pm

Those cheapie plastic reflectors and other taillight assemblies tend to shake themselves loose, as well... I had to tighten the holding screw for my bell today -- when I hit it, it turned upside down!

Title: Re: Loose Bottom Bracket
Post by jman on Apr 24^th, 2008, 10:49am

Your so right Paul, my headlight vibrated loose while on the Tour Dallas ride. The streets from White Rock Lake aren't the smoothest in my riding experiences that's for sure. I just caught the light in time as it had already slid upside down and had to carefully reposition it and tighten up as I carefully rode toward the last few turns of the ride.

Title: Re: Loose Bottom Bracket
Post by Opus the Poet on Apr 24^th, 2008, 1:54pm

Technically those were the crank bolts you tightened up, the bottom bracket is another animal entirely. I should mention that my Bottom Bracket came loose last year and required removal of the crank and tightening.

Notes for crank attachment to the axle, do not use grease or any other lubricant on square tapered cranks, You may need to grease some makes of splined cranks, follow the manufacturer's instructions in that regard.