Advertise on Bikeforums.net



User Tag List

Results 1 to 8 of 8
  1. #1
    Member
    Join Date
    Jul 2008
    Location
    Pflugerville, TX
    My Bikes
    Early 1990 Trek 950 MTB and Centurian LeMans Road (new to me!)
    Posts
    44
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    Crank replacement question-bolt removal?

    I'm a amature bike mechanic-basically, I''m fairly new to biking and I have a 80's Centruion LaMans that I ride. I've been using this bike as my learning pad for repairs as things break or I decide that I want to upgrade them. Most things have been pretty easy so far (rear derailure, handlebars, Etc).

    The current crank set is a biopace double with a fairly high tooth count so I've bought a new compact crank to try out, it's square taper also. I did some reading on crank removal and things went pretty well. I took off the dust caps, there was a Nut that I removed, then I used my crank removal tool to get the crank arms off. All that went pretty easily.

    Then I put on my new crank arms however I then noticed that the new crank arms had self extracting bolts to install. The bottom bracket still has the bolts attached from the previous crank removal making it impossible to use the new self extracting bolts.

    So, did I do the crank removal properly? Where the bolts that were on there previously supposed to come off during my crank removal?

    If they were not supposed to come off, is there a easy way to get them off so I can use the self extracting bolts that came with my new crank?

    Just to see how the cranks would look, I put the new cranks on and used the old nut to secure them in place. The cranks seem nicely secured and ridable. However, it does not look "nice" with the exposed nut/treads. I could find some dust caps and leave it as is but I just wanted to check with more experiencd mechanics to see if I was doing things correctly.

    Thank you for your time and help!

  2. #2
    Senior Member LesterOfPuppets's Avatar
    Join Date
    Sep 2008
    Location
    Vancouver, USA
    My Bikes
    My War
    Posts
    19,409
    Mentioned
    26 Post(s)
    Tagged
    7 Thread(s)
    You have a nutted bottom bracket there so the only choice is to use the nuts that came with. Make sure you get 'em tight.

    You'd need a different bottom bracket if you want to attach cranks with bolts.

    Nutted BBs are typically considered inferior, but I rode on them for several years without much trouble.
    1980ish Free Spirit Sunbird fixed * 1996 Mongoose IBOC Zero-G * 1997 KHS Comp * 1990-ish Scapin * Olde Western Auto Cruiser.

  3. #3
    Senior Member
    Join Date
    Aug 2010
    Posts
    125
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Sorry to steal the thread, but I'd thought I'd ask in here rather than start a new thread as it is sort of related?

    Anywho, I also just replaced my crankset on my bottom bracket which is of the square-taper, nutted variety. The drive side went on normally, however the non-drive crank didn't seem to go on too far, maybe a thread or two shy of fully engaging all of the threads on the crank-nut. It is cranked on there reasonably tight (but not overly), so should I be worried about this or should it be fine?

    It is an old 80's fuji with an uneven spindle length and a new, generic/no name japanese crankset.

    (however with the nondrive side a bit further out, it actually creates a nice symmetry between the cranks, whereas they were lopsided previously [drive side sticking out further])

  4. #4
    coprolite fietsbob's Avatar
    Join Date
    Jun 2010
    Location
    NW,Oregon Coast
    My Bikes
    7
    Posts
    38,842
    Mentioned
    20 Post(s)
    Tagged
    0 Thread(s)
    I would remove the self extracting bolts ring, It takes a tiny pin spanner to unscrew.
    May be a tool to buy , or turn the job over to someone who does have one..
    Then you can test fit the crank on your BB spindle.
    I expect the design of the crank is such that you need a different length of a BB.

    but that is not something that can be prescribed over text based .. this place.

  5. #5
    just pokin' along desertdork's Avatar
    Join Date
    Aug 2008
    Location
    the desert
    Posts
    1,033
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by hoyc View Post
    Sorry to steal the thread, but I'd thought I'd ask in here rather than start a new thread as it is sort of related?

    Anywho, I also just replaced my crankset on my bottom bracket which is of the square-taper, nutted variety. The drive side went on normally, however the non-drive crank didn't seem to go on too far, maybe a thread or two shy of fully engaging all of the threads on the crank-nut. It is cranked on there reasonably tight (but not overly), so should I be worried about this or should it be fine?

    It is an old 80's fuji with an uneven spindle length and a new, generic/no name japanese crankset.

    (however with the nondrive side a bit further out, it actually creates a nice symmetry between the cranks, whereas they were lopsided previously [drive side sticking out further])
    It might be worth pulling both crank arms, rotating the spindle 1/4 or 1/2 turn, and then reinstall the arms. There may be something about the current orientation of the arm-spindle interface preventing it from seating properly which could be resolved by doing this. It will also give you another chance to fully inspect the parts before reinstalling. You will want to mark the spindle before removing the arms, though, so you have a reference.

  6. #6
    Senior Member
    Join Date
    Aug 2010
    Posts
    125
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    I told my dad about it and he also made a good point of saying that it is possible they could be a mismatched set, thus may have a different sized hole? These were afterall a generic set that the local bike co-op ordered for me from their part supplier.

    Maybe I will try and remove just the non drive, and rotate 90'deg? And if that helps any, do the same with the drive-side.

  7. #7
    Shop Wench
    Join Date
    Mar 2009
    Location
    California
    Posts
    284
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by hoyc View Post
    Maybe I will try and remove just the non drive, and rotate 90'deg?
    Are you sure about rotating just the NDS?

  8. #8
    Member
    Join Date
    Jul 2008
    Location
    Pflugerville, TX
    My Bikes
    Early 1990 Trek 950 MTB and Centurian LeMans Road (new to me!)
    Posts
    44
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Thank you Lester for the response. That makes sense that the bottom bracket is setup this way-it being a nutted bottom bracket. I might end up buying a new bottom bracket since the cranks i bought were ISO and the bottom bracker is JIS. From what I've read on Sheldon Brown, you can sorta interchange them. So, I just wated to do a few rides and see if I liked the compact crank. If so, I'll buy the proper bottom bracket to install.

    Thank you again for you help!

Posting Permissions

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