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07-26-12 | 02:40 PM

#4

FBinNY

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Joined: Apr 2009

Posts: 39,897

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From: New Rochelle, NY

Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter

I'm not sure you have the facts straight. Normally double cranks mount both chainrings using the smae bolt with oneinside the arm and the other outside. If yours is that way than both chainrings must have the same bolt circle (BCD), be it 110 or 130mm.

Triples usually use 2 diameters, with the outer 2 sharing the same mount the way doubles do, and the inner having it's own smaller BCD and mounting directly to the arm. A typical triple would be 110/74.

Check your cranks and look at the arrangement, then measure to determine the BCD of the rings you need. If measuring bolt to bolt, refer to these charts to find the BCD

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