I have a Trek 1000 Road Bike with a Bontrager Triple front chain ring. The bike is a 2008 or 2009 model I believe. It's an 8 speed drive train. I'm going to change my Triple to a Compact double. My current BB is square tapered, the new crank uses ISIS. My question is on the size of the bottom bracket. The ISIS BB has 3 sizes 68 X108 / 68 X 113 / 68 X 118 : I'm not sure of the size I would need since my current Bottom Bracket is sized for a triple crank. I'm thinking the 108 or 113 Does any one have any suggestions? Thanks