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Chainring Spider(2 posts)

Chainring SpiderKen P
Jan 22, 2002 10:43 AM
I have some old cranks that I need to put new chainrings on, but I do not know the size of the spider to get new rings. How do I determine the size? You see rings listed as 105mm, 110mm etc.

It's the bolt circle diametercory
Jan 22, 2002 12:10 PM
If you scribe a circle that goes through all the bolt holes, then measure its diameter in millimeters, that's what they're talking about. You can also do it by measuring from the center of one hole to the center of the next (easier to do) and converting to BCD, but I forget the numbers.
If you have one around or can order it, the Bike Nashbar catalog explains this and even gives a template so you can order the right one. Or any bike shop can help you.