bottom bracket

joeygill

i am currently looking to upgrade my BB my bottom tube is threaded can i fit an external BB as long as i get the right size? or do i have use a BB like the one i currently use? http://www.chainreactioncycles.com/shim ... -prod34652 similar to what i use apart from mine is a truvativ BB i was looking at one similar to this http://www.chainreactioncycles.com/shim ... -prod41445.

nicklouse

You can fit whatever you want as long as it all matches.

External BB need suitable cranks.

Most external cranks come with the BB included.

The BB shell needs to be faced if you are fitting an external BB for the first time.

mini_death

If you're running square taper or similar (isis / octalink) then you must replace it with the same.

Same shell size, same length, same type.

You can only get an external BB if you upgrade your chainset to one that utilises an external chainset, such as a shimano hollowtech chainset. This is easily identified by the large axle and hole in the drive side crank. Other manufacturers do it differently, but they're all based on the same idea.

Hope that helps.

PS:
In my opinion your BB should be faced anyway as there's still the lip on the drive side of square taper BBs that should be flush with the BB shell. If there's a large gloop of paint preventing that it can cause premature wear and creaking.