Bicycle Mechanics - Swapping Cranksets

Hi everyone,

I recently decided to swap from a triple crank to a double (before we get into a triple v double debate, i have done alot of research and i got an amazing deal on a crankset).

The new crankset to go on the bike is a truvativ rouler, with a GXP BB and currently i am riding a shimano sora triple with external BB (i dont know if shimano have a cool name like GXP, but i guess it doesnt really matter for this).

The GXP BB was installed on a bike but not ridden, and when i picked it up, it appears that it is missing a seal on the drive side, ie. there is a black seal that says GXP on the non drive side cup, however, on the drive side, it looks different (there is about a 1mm recess from the lip of the BB cup and what appears to be the bearing, which is covered in blue grease).

My question has two parts,

1) can the truvativ crankset be mounted in the sora BB (and is this better or worse than the GXP one)

and

2) does it sound as though i am in fact missing a seal on the GXP BB.

Cheers :)

1) No, Shimano and SRAM/Truvativ BBs are not interchangeable.

2) Yes, it sounds like a seal is missing (because you definitely shouldn't be able to see the bearings and grease), hopefully you can find a replacement. Here is what it should look like:

http://www.chainreactioncycles.com/Images/Models/Full/19366.jpg

Thanks for your help, looks like im in search of a black o-ring? well at least thats what i have been able to work out from looking at your picture and the tech docs. So does anyone have any idea where i might find one of these?

What I can see does not look like an O-ring, but rather a seal designed or selected for that specific use. You can experiment with O-rings, or take it to a bearing dealer or perhaps a McMaster-Carr store, and see if they can match something up. Peruse the McMaster-Carr website to start to learn something about seals and how they are fitted.