How do I know the bolt pattern of a chainring?

Quoted post said:

Originally posted by Bonesnuggler
Hi, I'm trying to decifer what bolt pattern all my chainrings are. I'm pretty sure anything that
works on my track cranks are 144. Is there a way to just measure them? Thanks in advance. JC

Measure Center to Center between the adjacent bolt holes.
Convert your measurement by multiplying by 1.7
or

Chainrings are most often measured in reference to their Bolt Circle Diameter. BCD is literally the diameter of an imaginary circle that connects the centers of all the chainring bolts.

It is easier to measure the distance between adjoining chainring bolts . Use the chart below to determine what size rings you have.

74 BCD Rings: A = 43.5 mm, B = 74 mm
130 BCD Rings: A = 76.4 mm, B = 130 mm
135 BCD Rings: A = 79.5 mm, B = 135 mm
144 BCD Rings: A = 84.6 mm, B = 144 mm

Measure the distance in mm between the centers of 2 adjacent chainring bolts. Then go to Sheldon
Brown's site (sheldonbrown.comgloss bo z.htmlOpen ↗) and find the distance you have in the
3rd column of the table. The BCD can then be read from the first column.

David

Bonesnuggler said:

Hi, I'm trying to decifer what bolt pattern all my chainrings are. I'm pretty sure anything that
works on my track cranks are 144. Is there a way to just measure them? Thanks in advance. JC

Thanks guys. I'm all set. JC