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BB Grumbling

S_J_PS_J_P Posts: 908
edited July 2007 in MTB workshop & tech
I noticed on yesterdays ride a regular clicking from my BB area every half-turn on the cranks under power. When I returned home, slipping the chain off the chain-ring I found that whilst the cranks turn with very little resistance, and there's no lateral movement, there is a grumbling from the BB bearing.

The bikes a year old (Giant Terrago with Truvativ cranks), is it likely that I need a new BB bearing?

Posts

  • alfabluealfablue Posts: 8,497
    Very likely, the original fitment may not be of the highest quality (as BB are invisible), especially if you have done a reasonable mileage.

    Apparent BB clicking is sometimes pedal bearings, chainring bolts or even seatposts, but as it grumbles when you are off the bike then BB is most likely.

    [Edit: The Truvativ Power Spline originally fitted is a £12 part, so may not be the best - worth upgrading to a higher quality part, however there might be a problem getting an alternative to fit the 12 splined cranks, you may only be able to get the same part again unless you change the cranks too - it is not well rated on MTBR]
  • alfabluealfablue Posts: 8,497
    You could get a Shimano Deore splined chainset for £35 and a Deore Splined BB for £12 from Chainreactioncycles. Probably the cheapest acceptable way to improve the situation that will allow a choice of replacement parts for a while into the future.
  • S_J_PS_J_P Posts: 908
    Thanks for the heads-up. It looks as though I'm a little stuck with what I've got! It's no as though I've done mega-miles either!!

    The chain-rings are fine, so I'd rather just replace the BB, but if it's the only 12-spline one around my options really are limited.

    Thanks for the links, I'll take a look at other alternatives too, if I'm spending £50 on another cheap BB kit I think I'd rather spend a little more on something which will last from the outset!
  • alfabluealfablue Posts: 8,497
    I think the Deore setup would be a level above what you have, however if prepared to spend more, the Shimano LX Hollowtech II should be good, it requires a Hollowtech II BB, about £100 for the complete setup. Also, your bottom bracket shell would need facing by the LBS to keep BB cups parallel. My LBS faced shell and fitted my Hollowtech II for £15.

    These make the BB feel much stiffer under acceleration.
  • S_J_PS_J_P Posts: 908
    I've just been browsing Wiggle and CRC, and saw the (discounted) Hollowtech II, however the What MTB reviews do mention limited bearing-life and question the durability of the aluminium rings.

    The M580 BB versions are just £70, with the M780's coming in at £90, so they're pretty reasonably priced though verses the equivalent options from the opposition.
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