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Technical & Reference Section => Tech and Restoration => Topic started by: Jon.l on September 20, 2014, 11:24 AM

Title: Bottom bracket adjustment
Post by: Jon.l on September 20, 2014, 11:24 AM

Hi guys, I have managed to bag my self a mid school diamond back bmx I reckon it's year is approximately 1996 ish ( thanks to bike pedia and google!. Any ways this will be my first attempt ever at a restore/ rebuild with a bit of customisation thrown in for good measure.

My question is ( I'm guessing the first of many). I have been reading up about bottom brackets and that if they are not adjusted correctly- namely adjusting the lock nut onto the cone that the chain will just keep jumping off. How difficult is it to adjust these? Are there any hints and tips you guys know of? If any one knows it will be on here I'm pretty sure!  "help"

Title: Re: Bottom bracket adjustment
Post by: CustardLips on September 21, 2014, 12:31 AM

Fook reading up on it... get your spanners out. Strip it, clean it, put it back together.  :daumenhoch:
Any problems give us a shout.  ;)

Title: Re: Bottom bracket adjustment
Post by: MartyC on September 21, 2014, 04:10 AM

Chain will only jump off it is out of alignment and/or your BB is really loose so that the chainring turns elliptically (out of round).

Tighten it up and back off the bearing race against the lock nut and you shouldn;t have any problems.

For one Piece cranks:

http://www.parktool.com/blog/repair-help/one-piece-bottom-bracket-service

For newish school three piece cranks (but covers Euro sized bb):

http://www.parktool.com/blog/repair-help/bmx-three-piece-crank-service

Title: Re: Bottom bracket adjustment
Post by: Jon.l on September 21, 2014, 02:23 PM

Thanks guys. Thanks for the links Marty! :daumenhoch: