Square taper chainset upgrade

trek_dan

Hi, I want to change my cranks for shorter 170mm length ones, my bike (2009 Trek) has an integrated square taper BB so I was just wondering what my upgrade options are? Most of the chainsets I've come across on Ebay etc seem to be for external type BB's. My current chainset is the standard FSA Vero that came with the bike, while going for the shorter length I was thinking I might aswell upgrade to something stiffer and lighter. What are my options, will Shimano eg 105 etc fit the square taper BB? Thanks, Dan

TommyEss

An external bottom bracket is only £15-20 anyway - why not just upgrade to 105 with external BB? (Depending on how long your current BB has been in there, it might not be a bad move to replace to current square taper regardless)

trek_dan

Does an external BB fit the frame in the same way? I think this was the key piece of information I was missing, doh!

TommyEss

Yep, the square taper/external/GXP/Ultra Torque part of the name corresponds to the cranks, the thread corresponds to how it fits in your bottom bracket shell (normally it's a choice between Italian or English threading)

If you look at a 105 external bottom bracket, it'll come in a couple of flavours, so you pick the one that fits your frame threads, and then get cranks to match the BB.

At a guess, I'd say your Trek has English threads - but you can double-check the product details on line, or take out your existing, where it'll have it written on there somewhere.

Monty Dog

Most external bearing chainsets come with bearings. You frame takes a regular BS thread x 68mm BB, only Italian-made ones come with Italian threads.

desweller

The downside of external bearing type BBs is that they hang out in all the bad weather and muck. So they don't last very long. I've reconditioned two on the same bike in the last three years.