Chainset Swap

Sutton_Rider

I've got an Ultegra 6800 50/34 chainset and want to swap out the 34 for a 39. I assume it will all fit and work. Can anyone confirm please?

Ben6899

I think a run-of-the-mill Shimano 39 inner will have a 130mm BCD whereas your compact cranks will have a 110mm BCD. You might be able to get your hands on a 39 with 110mm.

shirley_basso

Will be fine for a 4 arm chainset. BCDs all the same. Ben is incorrect in this case as 6800 is a 4 arm chainset.

Ben6899

Ah I see! Happy days, OP.