Originally Posted by charlesw
Thanks for the help, I think I understand. Not sure what a BCD is.
However, you are right- it is a 5-bolt chainring. I measured from the middle of one bolt to the middle of the next adjacent bolt and the measurement was 2 3/4, which is 69.85 mm.
That doesen't seem like a standard measurement.
here is a picture how I measured it:
Thanks a ton for your help!
I didn't think that moving from the small chainring to the large one would be a large jump.
What do people normally do when they have a large chainring? Get a larger 'smaller' chainring and also install it?
Got me stumped.Try measuring as accurately as possible c-c of two NON ADJACENT adjacent bolt holes and divide by .951, convert to mm and report back. You can double check that measurement by measuring center of crank bolt to a bolt hole center and multiplying by 2. That should be Bolt Circle Diameter. What's the tooth count on the rings that are on it now? A 52 or 53 large ring would typically be used with a 42 or 39 smallring, but that isn't concrete.