Bicycle Mechanics - BB Creaking
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04-08-03, 02:52 PM
I went riding Friday and noticed that when pedaling especially under load, there was an odd sound. At first I thought it was the chain slapping. I then realized it was coming from the BB/crank area. Is this a sign that it's starting to go, or does it just need to be lubed up? I have probably close to 200 trail miles on it and many, many hours of trainer time this winter adding up to the equivalent of probably over another 200 miles. Could it ust be worn out at this point? It's my first MTB, which was in the starter price range, so it's probably not the best BB, and the manufacturers web page does not say what kind it is. It's a solid HT frame, and have no problem upgrading since the frame should last a very long time.
04-08-03, 03:42 PM
The creaking is usually in the threads and not in the BB itself. If you have a BB tool you might try just tightening it.
I had a similar problem not too long ago. I took the bike --- not having a BB tool --- to my LBS. Turns out that some moisture had gotten into the BB. They dried it out, put it back together, and everything was fine.
04-08-03, 07:03 PM
IF the frame is aluminum and the threads arent greased enough or they dont have teflon tape on them then the BB can shift ever so slightly and rub the threads together which makes the noise you are hearing. In this case the BB just needs to be pulled and the BB shell cleaned out. Then apply grease liberally to the threads and reinstall it. Also check the torque on the crankarms themselves although there is a bigger chance that it is the BB itself. When reinstalling the BB the torque spec should be around 260 to 350 in/lbs and the crankarms to around 32 ft/lbs. This is an easy fix at the LBS and I would hope they would not charge very much for this.
In the shop I often find the creak being generated by a missing crank bolt washer on the Simano Octalink type crank. Not only will this be a continuous source of trouble it will also ruin the crank arm.
Mine was creaking last week, and I took it apart (borrowed some tools from a friend) and lubed the bearings and threads up. Hasn't made a sound since.
04-10-03, 02:53 PM
I've got this problem too. I've got the tools to fix it. But no torque wrench. How critical is the torque wrench? If I over tighten it will something bad happen? :o
04-10-03, 09:54 PM
For those of you who are not down with the mechanic lingo d jingo, brinelling is when a bearing becomes "indexed" or has a place where it wants to sit rather than roll smoothly. This is often true in headsets where they develop a strong notion to click into place when the wheel is pointed straight forward. I do not believe that this could occur on your bike though since the bottom bracket is likely a sealed cartridge unit meaning that there is no adjustment on the bearings and therefore overtightening it will not harm the bearing race surfaces. I gave some torque specs above in an earlier post but as long as the bottom bracket it sufficiently tight (that doesnt mean use a cheater bar) and the crank bolts are snug then things should be fine. This is a good job for the shop to handle but if you are certain you want to undertake it then good luck. Just be sure not to cross thread the bottom bracket when reinstalling as you will damage the frame - then the mechanics at the shop will have to re thread the bottom bracket shell and will probably laugh at you when you leave. Up to you.
04-10-03, 10:42 PM
HEHE, I had the same problem today for the first time ever. Took off the cranks at my shop at work, took of the BB cap and was able to tighten the BB about 1 full rotation with the spanner. Didn't make any noise coming home from work.
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