I just bought a used 56cm 613 and will be switching over components from my 58cm R1000. When I bought the frameset from a teammate, I noticed he had 173.5mm cranks, while my R1000 has 175mm cranks. He said that is standard in those size of bikes. Will I have any problems putting the 175mm on the 56cm, or should I buy some 173.5mm to put on the 56cm frame? I am 5'11 &3/4 with a 33in inseam. Is this a big deal or not? Will the length in crank enhance performance or be a detriment?(I know that last sentence sounds funny.) Sprinting? Climbing? I am using this bike to race. Thanks for the advice.

Cheers

You can measure the BB heights of the two bikes to know how much room you'll have with either crank. In either case, 2.5 mm is not very much of a difference at all.

Will the length in crank enhance performance or be a detriment?

Shorter cranks tend to make it easier to spin. Other than that, it's all about adaptation. BTW, the standard length is 172.5, not 173.5 :)

It's most likely you won't notice any difference between the two, but if you are sensitive to small adjustments on the bike you might.

The 2.5mm difference could mean a slightly different saddle position: need to move the saddle back to compensate for the 2.5mm shorter cranks and drop your seat height to compensate for the difference also.

Longer cranks theoretically give you a bit more torque because it's a longer lever you are pushing, but are harder to spin because they are longer.

I have 172.5mm on my trainer bike and 175mm on my road bike and switch between the two all the time. In fact I have 172.5mm drive side and 170mm non drive on my trainer bike due to a leg length imbalance and have no problems switching between the two. On my road bike I have Lemond LeWedges under the left foot to compensate for the leg length imbalance.