Rear Derailluer Danger with Compact Cranks! Advice Solicitation - Tom D. you've never let me down before

Triathlon Forum
1

Howdy -

Just switched to compact cranks - 52/34 (Might try to find a 50). But for now that’s what I’ve got. FD = Ultegra, RD = DA2005

I’m concerned because I can’t seem to find a good balance of chain length. What is too long on the 34 seems way too short on the 52 and the RD gets so that the pulleys are either lined straight up and down or even so far as to have the lower one closer the front of the bike than the upper.

Is this arrangement dangerous?
Anybody got a spare 50 tooth ring 110mm BCD?

Thanks

2

I think you may find that an 18 tooth diff between big and small ring is a bit too much.

3

I hate to say it, but you are running a silly combo. If you go 52, you should run a 36. The biggest you should run is 50 with a 34, but more appropriately a 48. You should also consider using a Long Cage Derrailleur. In any case, drop the 52. It has little value for most mere mortals, especially for triathlon.

4

Just avoid cross chaining the top (or bottom) two or three cogs and you shouldn’t have much of a problem (aside from having an 18-tooth gap between your chainrings).