Advertise on Bikeforums.net



User Tag List

Results 1 to 9 of 9
  1. #1
    Senior Member North Coast Joe's Avatar
    Join Date
    Dec 2012
    Location
    high above the pounding surf of Lake Erie
    My Bikes
    1 commuter, 2 fixed gears
    Posts
    246
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    Bottom Bracket Advise, Please.

    Thanks for taking the time to read through this!

    I had a pedal strip out of the crank arm while under load on my 2011 Trek 3900 Disc MTB. That was a mystery of it's own on a bike that does have fairly heavy mileage, but I digress.

    I am new to this whole bicycle mechanics thing, but have some experience with a total rebuild of another, much older bike.

    After pulling the crank arms, I cleaned up the bottom bracket and took a look at it's condition. It's tight as far as any slop either end-to-end or up & down, even when using the crank arms to lever it around. What I feel when I rotate the spindle is considerably more "gravelly" than the silky smooth feel of the cup/cone/loose ball BB that's on my older bicycle. When I put the crank arms on the BB turns very freely and the cranks swing easily with not too much noise....but again, more noise than the cup-n-cone one. Is that "normal" for a cartridge type BB? Or..."as long as it's torn apart..."

    One more quick question on this repair, please. I went with the same model/brand of crankset, but went 4 teeth more on the two smaller chainrings and 6 more on the largest. Is there a formula for lengthening the chain....or will the old number links + 6 work?

    Thanks again!

  2. #2
    Senior Member
    Join Date
    Apr 2009
    Location
    New Rochelle, NY
    My Bikes
    too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
    Posts
    22,534
    Mentioned
    69 Post(s)
    Tagged
    1 Thread(s)
    A rough or gravelly feel isn't normal, and usually indicates some dirt or rust contamination and/or wear. If this is a typical cartridge style BB, your options for service are limited. You might want o take a look and see if it's at all serviceable, otherwise since it shows no play, go ahead and use it until it dies.
    FB
    Chain-L site

    An ounce of diagnosis is worth a pound of cure.

    “Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin

    “One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN

    WARNING, I'm from New York. Thin skinned people should maintain safe distance.

  3. #3
    Senior Member North Coast Joe's Avatar
    Join Date
    Dec 2012
    Location
    high above the pounding surf of Lake Erie
    My Bikes
    1 commuter, 2 fixed gears
    Posts
    246
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Thanks, Francis. I'm still holding $.50 in escrow for you after I used your wheel dishing trick on two wheels. Ya' never know...I may have to re-dish again!

  4. #4
    Senior Member
    Join Date
    Apr 2009
    Location
    New Rochelle, NY
    My Bikes
    too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
    Posts
    22,534
    Mentioned
    69 Post(s)
    Tagged
    1 Thread(s)
    Quote Originally Posted by North Coast Joe View Post
    Thanks, Francis. I'm still holding $.50 in escrow for you after I used your wheel dishing trick on two wheels. Ya' never know...I may have to re-dish again!
    let me know when it's enough to buy a few beers then I'll come out to collect.
    FB
    Chain-L site

    An ounce of diagnosis is worth a pound of cure.

    “Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin

    “One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN

    WARNING, I'm from New York. Thin skinned people should maintain safe distance.

  5. #5
    coprolite fietsbob's Avatar
    Join Date
    Jun 2010
    Location
    NW,Oregon Coast
    My Bikes
    7
    Posts
    3,335
    Mentioned
    48 Post(s)
    Tagged
    0 Thread(s)
    so much of the bike production has gone over to fit and forget BB assemblies ..
    If you got dirt in the bearings , take out the BB cartridge, and put a new one in ..

    UN type BB are disposable Priced and designed to be so.

  6. #6
    Senior Member CACycling's Avatar
    Join Date
    Feb 2008
    Location
    Oxnard, CA
    My Bikes
    '08 Fuji Roubaix RC; '07 Schwinn Le Tour GS; '92 Diamond Back Ascent EX
    Posts
    4,450
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Regarding the chain length part of your question, if it was sized properly before, it will be short now. But, we don't know if it was sized properly before so either replace or add the number of links necessary to get it to the correct length.

  7. #7
    Senior Member North Coast Joe's Avatar
    Join Date
    Dec 2012
    Location
    high above the pounding surf of Lake Erie
    My Bikes
    1 commuter, 2 fixed gears
    Posts
    246
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Thanks, CACycling. Yes, it was the original and seemed to be fine for all gear combos and easy to remove the rear wheel. I'm replacing it, as well as the crankset and cassette, so will just add the 6 to the original chain link count. Probably replace the BB, too...it just doesn't feel right.

    Just as an addendum: looking around on the web I can find several 122.5mm spindle length BB's but only a couple at the 123mm length specified by the crankset manufacturer....close enough?

  8. #8
    Senior Member CACycling's Avatar
    Join Date
    Feb 2008
    Location
    Oxnard, CA
    My Bikes
    '08 Fuji Roubaix RC; '07 Schwinn Le Tour GS; '92 Diamond Back Ascent EX
    Posts
    4,450
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by North Coast Joe View Post
    Just as an addendum: looking around on the web I can find several 122.5mm spindle length BB's but only a couple at the 123mm length specified by the crankset manufacturer....close enough?
    That's a bit less than 1/100" shorter on each side.

  9. #9
    Senior Member
    Join Date
    Jan 2014
    Posts
    260
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    Pretty sure how worn the taper is, or even how tight the cranks are, or even the tolerances of the BB shell make a bigger difference than that. Insignificant.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •