Notchy press fit BB

larkim
larkim Posts: 2,474
edited April 2017 in MTB workshop & tech
Removed the cranks last night for the first time after 2.5 years and obviously in need of a good clean up. Avoided degreaser on the BB itself, just cleaned up with cloth and a little water. Drive side was still smooth but non-drive side the bearing was a bit dry and notchy feeling.

Are there any DIY options for smoothing out the bearing - BB is a BB71 shimano one - couldn't tell if I could extract the bearing from the BB unit itself or not. Or is it a case of a new BB (only £23 or so, so not a disaster). Or alternatively, what damage is likely to result from having one side of the bearings not running as smoothly as they should?

I presume the bearing damage per se would only be to the BB itself (not the shell)? Given the option, I'd rather not spend on replacing it at the moment, but now that I know it is on its way out I will of course have to replace at some point - just interested in whether riding it in the current state will cause more expense later if I delay by a month or so?
2015 Canyon Nerve AL 6.0 (son #1's)
2011 Specialized Hardrock Sport Disc (son #4s)
2013 Decathlon Triban 3 (red) (mine)
2019 Hoy Bonaly 26" Disc (son #2s)
2018 Voodoo Bizango (mine)
2018 Voodoo Maji (wife's)

Comments

  • larkim
    larkim Posts: 2,474
    OK, I'll take the resounding silence as "Don't be a blithering fool, get it replaced asap or YOU WILL DIE!!!"

    :-)
    2015 Canyon Nerve AL 6.0 (son #1's)
    2011 Specialized Hardrock Sport Disc (son #4s)
    2013 Decathlon Triban 3 (red) (mine)
    2019 Hoy Bonaly 26" Disc (son #2s)
    2018 Voodoo Bizango (mine)
    2018 Voodoo Maji (wife's)
  • The Rookie
    The Rookie Posts: 27,812
    If the bearing seizes the inner can spin on the crank axle resulting in you needing a new crankset.

    Personally I'd get it replaced but not familiar enough with that specific BB to know if you can just do a bearing, although I know you can with the threaded HT2 despite Shimano saying you can't!
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.
  • larkim
    larkim Posts: 2,474
    I think its the cheaper end of the BB market - lots of plastic involved so I suspect getting the bearings out would be less than ideal, and by the time I've done that I could probably have fitted a new one, though I've now read some horror stories of getting them out of the frame too. Some of the reviews on CRC were less than flattering!

    Thanks for replying though!
    2015 Canyon Nerve AL 6.0 (son #1's)
    2011 Specialized Hardrock Sport Disc (son #4s)
    2013 Decathlon Triban 3 (red) (mine)
    2019 Hoy Bonaly 26" Disc (son #2s)
    2018 Voodoo Bizango (mine)
    2018 Voodoo Maji (wife's)
  • keef66
    keef66 Posts: 13,123
    ^ wot he said. If it seizes it could conceivably damage the spindle. Although if I remember correctly the actual bits the spindle slides through are plastic, so less likely with Shimano BBs.

    You'd probably get away with it for a while. Since it sounds like it's toast you could always try prising off the cover / picking out the seal and squirting some grease in there?

    I've seen dozens of posts / videos of people doing DIY bearing replacements with the threaded HT2 cups, but none so far for the press-fit ones. That's not to say it's not possible, more that I haven't looked. My BBs seem to be pretty long lived so I figure for the reasonable cost of a replacement every 5 or more years I CBA picking out seals and faffing with bearings.

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