Bottom Bracket Size for Specialized Roubaix Elite C2 2009 I think my bottom bracket has worn and I would like to replace it.  I was looking at the Shimano 105 BB.  BikePedia lists the size as 68mm, which is fine, but there seems to be another dimension.  I can get 68 x 109 mm or 68 x 118 mm.  Is it possible to work out which size I need without removing the current BB?

update
I'm not sure which of the below answers is correct.  In the end I bought a SM-BB6700 Bottom Bracket BC1.37 which worked fine (techdocs here).
It is best to remove your current bottom bracket to check, but as a rule of thumb, a triple (3 gear) front crank uses a 118mm. A double (2 gear) front crank uses a 109mm.