Bottom Bracket size?

[Chance3290]

I just found a Shimano R700 compact crankset for my TREK 5000. I believe I'll need a new bottom bracket and, since I've never changed one, does anyone know which size is required. The Ultegra BB-6600 is the BB I'm planning on going with, but it has two size listing; 68 and 70.
And my 5000 is still an Ultegra 9 speed. Everyone is telling me that the compact crankset will work fine with 9, as well as with 10 speeds. I hope they're right.

 

[artmichalek]

It's most likely English thread (68mm).

 

[Chance3290]

It's most likely English thread (68mm).

Yup..you are correct, Sir. I found it. Thanks.

 

[John M]

I just found a Shimano R700 compact crankset for my TREK 5000. I believe I'll need a new bottom bracket and, since I've never changed one, does anyone know which size is required. The Ultegra BB-6600 is the BB I'm planning on going with, but it has two size listing; 68 and 70.
And my 5000 is still an Ultegra 9 speed. Everyone is telling me that the compact crankset will work fine with 9, as well as with 10 speeds. I hope they're right.

Yes, you will need a new BB since the R700 uses the integrated type cups as opposed to the ISIS drive that the 9s shimano stuff uses. Unless it was modified, your Trek is for sure a 68mm English thread BB, and the new crankset should work fine with the 9s.