Originally Posted by TheRCF
Can I switch to a 50/34 without changing to a compact crank too?
What makes it "compact"?
If it isn't the rings that make it compact, what is the advantage of a compact set-up compared to one with the same front rings that isn't compact?
Physically, your chain cannot tell what kind of crankset you have. A 39t chainring is the exact same on the 130mm standard crankset as the 110mm compact crankset. This measurement is the bolt-circle diameter of the 5 bolts holding the chainring to the crank.
Most likely you've got a 130mm BCD crank and the smallest you can put on there is a 38t. To figure out which you have, measure the spacing between two adjacent bolts:
A 130mm bolt-circle would measure 76.4mm between bolts and a 110mm compact-crank would measure 64.7mm. I run a 50/34t crankset with 13-24t rear most of the time. If I need even lower gears, I've got a 13-26t or even a 13-28t if necessary. A 50/34t crankset with 13-28t rear would effectively give you two lower gears than you have now.
