How to check bottom bracket size

Question

I am looking at investing in some Profile cranks, but I need to know what size bottom bracket I currently have.

Also, if anybody could tell me the bottom bracket size of the GT bump 06 then that would be more useful.

One more thing - taking the bike to a shop is not an option as the nearest shop is several miles away and like to rip me off. Like, a lot.

Answer 1

It looks like a loose ball type.  Can't tell you the size but it is the 8 spine type that should be standard. You will have to remove the crank arm to be sure. See the link below you should not need the crank puller.

Answer 2

http://www.bikepedia.com/QuickBike/BikeS...

Unfortunately this bike had 2 different sizes- American is the large diameter that looks like it could fit a one piece crank (and it would). I don't know if this same BB was used in UK models or not.

I would email danscomp.com and ask them what they suggest.

Um, both Profile and GT used Lasco to make their cranks so unless there is a distinct upgrade you probably already have "Profile" on there.

Answer 3

there's only two size the american used on almost all bikes and the italian which is used on the top end italian bike if your bike was built by a non italian company chances are it's an american bb