Good afternoon all! In previous questions, I've mentioned that I intend to rebuild my 2000 Trek 7700 Multitrack. Well, I'm beginning by replacing the bottom bracket. According to the spec sheet I got from Vintage-Trek.com, the BB is Shimano BB-LP27 73x113. I've searched for BB-LP27 73x113 and come up empty. I assumed this is an obsolete part, but there must be a current part which will serve the same purpose. How do I decipher what current part would work in this application?

I'm adding the technical sheet I found on vintage-trek.com.

2000 Trek 7700 Multitrack  Technical

  • 1
    The critical numbers for a BB cassette are the shell width, the length, and the "offset". Unfortunately, determining those from an existing cassette is not always easy, but presumably the length is 113 and the shell width is 73. A 2x crankset sometimes has a zero offset, or maybe 5mm, but a 3x is almost always around 10mm. (This basically determines the clearance between the frame and the small sprocket.) However, it appears that most newer cartridges are designed to have shims used to set the offset, vs selling ones with specific offsets built-in. Jul 15, 2015 at 17:12
  • The LP is apparently for Low Profile and the last Shimano documentation for that series is dated 1999 which coincides well with your bike's year. Jul 15, 2015 at 17:31
  • 4
    Shimano BB-UN55 73-113 is what you'll pretty much use (UN54 is a cheaper version, but its like a 15 dollar part to begin with...)
    – Batman
    Jul 15, 2015 at 17:47
  • I took my bottom bracket axle into the LBS and let them measure it. If it was wrong they would swap it. Another reason to patronise the brick and mortar shops not buy on-line.
    – Criggie
    Dec 8, 2015 at 9:25

1 Answer 1


Here's the Shimano datasheet. So we know it's a square taper, ISO-threaded BB. So a UN54/UN55 is the replacement part (take the UN55).

73 is the shell size: 73mm.

113 is the spindle length: 113mm.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.