Sunday, September 11, 2011

Bottom Bracket Rescue

Between the crank arms, nestled in a cylindrical hole in your bike frame rests a device called the bottom bracket.   In essence, it's a couple of sealed bearings inside a threaded tube with a small axle running through it.   After years of abuse, the bearings can fail, leading to a crackling noise when pedaling.   

Today, I pulled my very first bottom bracket, a fairly straightforward procedure, provided you have the right tools.  The tools themselves are cheap - about $20 on sale at my local bike shop. There are also plenty of how-to videos online, so I'll skip that.   Here's what I learned... 

Sometimes, the bottom bracket isn't bad.   My local shop didn't have the correct size bracket, but the mechanic checked out my bracket and thought it turned smoothly.   She suggested that grit that gets into the threads can also make a crackling noise.  

So, I gave it a go and surprise, surprise, my bottom bracket is fine.   The crackling noise is now completely gone.  So before running out to replace your bottom bracket, try cleaning it, regreasing, and reinstalling it first.   Oh, and don't be surprised if the bottom bracket comes out looking like a rusty mess.  Mine sure did, but it cleaned up nicely. 

Bottom bracket from my GT Terra Mountain Bike

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