Joined: Jul 2015
Posts: 7,413
Likes: 3,253
From: NW Oregon
Bikes: 1982 Trek 930R Custom, '91 Diamondback Ascent w/ XT, XTR updates, Fuji Team Pro CF road flyer, Specialized Sirrus Gravel Convert, '09 Comencal Meta 5.5 XC, '02 Marin MBX500, '84 Gitane Criterium bike
5 spoke crank, right? 110 bcd, most likely... run a search on Ebay for a "middle triple xx t 110 bcd" chain ring with same tooth count as present ring... place your tooth count where the x's are in the search i typed...
4 spoke crank? 104bcd.... is the ring attached with RIVETS, instead of an allen screw/slotted nut? you'll need to get an entire crank assembly with same tooth counts on the 3 rings.... if it has screws/nuts, then you can replace just the middle ring...
the screw mounted outer and middle rings can be removed/replaced without pulling the crank arm... inner ring will require removing the crank arm... the small inner rings rarely wear out, btw...
the "BCD" (base circle diameter) measurement is sometimes listed on the drive side crank arm, and might also be stamped into the chain rings... look at both sides of the chain rings... some are stamped on the outside, some on the inside....