BB Dimensions
I don't know what the dimensions are for trek but it's easy to measure. Turn the frame upside down and measure the BB in millimeters. There are 3 sizes: 68, 70 & 73. That tells you which BB to buy. The next most important measurement is the width of the spindle in mm, they range anywhere from 106 to 137 depending on your crank set and number of chainrings. (The spindle is the axle the cranks are bolted to.) Any bike shop can help you with this. If it's a trek dealer that's even better. Worst case, call trek. They advertise in all the mags and usually have an 800 number.
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ljbike