Exactly what I have... lower the der when you mount the new cranks. It'll work fine.

FWIW, I have a 50/34 (with campy 9-speed for the rest of the drivetrain) and use a triple FD and (after some adjustment) have not had any problems.

do you shift via friction?

^^^what kind of frames will not allow this and does the OP have this kind of frame?



OP the crank that you get will have a recomended bb size. A three ring set up is inteded to have the middle ring set to access most of you cogs and the big ring really only set up to reach the first 3-4 cogs. Thus, your 3 ring bb is longer. With a CC you will want to have more gears accessed by the big ring and so you want a bb that is short. If fact, the FSA CC recomends a short BB and you will often hear about the chain rub-n the outer 50t ring if you try to get to the first two cogs while in the inner 34t ring. You don't really want to be able to use those two cogs with the inner ring anyhow due to cross so it is not a big issue [but it drives some nuts and the spend a hell of a lot of time try-n to do the math and pick a bb that will yield no rub at all]

"^^^what kind of frames will not allow this and does the OP have this kind of frame?"

Some touring and BOB-ish hybrid frames require compact triples or MTB triples because the chainstays are curved out to accommodate a rear dropout width of 135mm (for those wanting flexibility to use disc brakes, etc.). Short BBs will result in interference between the chainrings and the chainstays. This can be a problem with either inner or outer chainrings, depending on how steeply the chainstays are curved outward from the BB, and how short the spindle length is and how large or small the granny is. Smaller grannies have less chance of rubbing. A compact with an inner ring of 34-36 teeth will have a bigger radius than a touring triple granny of 26, and so a greater chance of interference.

Chainline and avoiding cross-chaining is a separate issue.

As far as avoiding interference from the triple front derailleur rear cage crossmember and the chain when in low gear combinations, it really isn't a problem unless you have non-standard cogs, say a mostly road gear group mated with a single large inner "bailout" gear. Shifting from that bailout gear to the gear next to it while in the smallest front chainring might cause chain interference with the front derailleur cage, especially if it is a double.

Sorry, my previous post was confusing. My present bike has a triple. I am building new bike. I am in the process of choosing the components. I want to use a compact crank because I think the simplicity of it makes it trouble-free. I was not sure which FD to use.