DO I NEED A COMPACT OR STANDARD CHAINRING?
It is important that the Bolt Circle Diameter (BCD) of a chainring matches that
of the crankset, or they simply won’t fit.
SO WHATS THE DIFFERENCE?
-130mm or 135mm BCD (STANDARD):
These cranks are typically fitted with 39/53t or 39/52t chairing combinations,
and will only accept a minimum count of 38 teeth on the middle ring.
This gearing is usually sufficient for the competitive cyclist on UK roads.
-110mm BCD (COMPACT):
These cranks use smaller chainrings than a traditional road crankset
(typically 34/50 teeth) and these low ratios have proven to be popular with
fitness, recreational and sportif riders looking for less weight than a
triple chainset.
HOW DO I KNOW WHAT SIZE BCD I HAVE?
On most chain rings it will have the size of the BCD written on the ring
somewhere. If this is not the case then you need to measure the distance
between the two adjacent bolt holes:
