• 10-06-2019
    1995/96 Trek 7000 ZX bikes fitted with reverse-threaded square taper BB's?
    I'm rebuilding a 1996 Trek 7000 ZX SHX and a 1995 Trek 7000 ZX. Since I'm getting rid of the old STX/STX-RC cranksets, I also removed the existing square taper BBs. Strangely, both existing BBs seemed to be reverse threaded, with the fixed cup on the non-drive-side and the floating plastic spacer cup on the drive side!
    One BB had markings I could read: Shimano Japan, BB LP-25, VIA 73, BC 1.37 x 24
    The 7000 ZX is supposed to have a 73mm English thread BB shell, so that fits.

    Speculating here -- maybe Trek wanted to adjust the left/right position of the spindle ends and it was cheaper to use this reverse-threaded BB than to change crankarms or frame? Any ideas? I'm just going to be putting in a normal Octalink cartridge with new crank on one, and external bearings/crankset on the other.
  • 10-07-2019
    Yes you are right the Old Shimano bb's are odd locking in on the non drive side.
    The BB threads are standard BSA so just buy a new Shimano square tapper BB and all is good.

    Happy cycling

    Sent from my SM-T590 using Tapatalk
  • 10-07-2019
    What they said. Weird tweak to Shimanos cheap BB design. Never knew why, but there it is.

    Remove, replace, ride, no worries.
  • 10-07-2019
    Thanks, folks! It's amazing how much I learn in working on 20+ year-old bikes.