Bicycle Mechanics - need help finding the right chainrings
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01-19-06, 04:38 PM
My son & I are building a cyclocross (semi-beater/commuter) bike for me to ride when the weather's bad (when I don't want to commute on my roadbike). We bought a cyclocross frame and harvested some parts off my old Trek roadbike and have bought the rest. It was all built except for chainrings and the chain (and of course the adjustments to the derailleurs, etc.). Using the old Shimano RSX cranks, we wanted to put new chainrings on (the old ones were no longer good) and ordered some Truvativ ones--our criteria were to find chainrings that fit a 5 bolt shimano 130 pattern, and the big ring is has to be 47 or 48 b/c need to use a top pull derailleur;and the we want ramped rings. The rings that came didn't fit, because the holes were too far apart, i.e., the circle describing the lineup of the holes was a bigger diameter than the circle describing the holes in the crankarms.
Does anyone know what we should do? Know how to find a compatible set of rings? Or do we have to buy new cranks?
01-19-06, 04:42 PM
The RSX is probably 110mm BCD. Return, or sell, or use the 130mm rings somewhere else and get yourself some "compact" rings (the current name for the 110mm BCD).
Actually, before you go get the 110mm rings, measure the crank to make sure. The adjacent "hole-to-hole" measurement for 110mm is 64.7mm. http://www.sheldonbrown.com/gloss_bo-z.html
01-19-06, 04:57 PM
Sure enuf, I just went out & measured and the holes are 64.7mm apart, center to center. If I go to a compact, will that work w/ my derailleur? We put on a Shimano Deore LX ("for 44/48T top, 66-69 o").
01-19-06, 05:24 PM
...If I go to a compact, will that work w/ my derailleur? We put on a Shimano Deore LX ("for 44/48T top, 66-69 o").
Yes - a 48 tooth chain ring is the same outer diameter regardless of the BCD.
01-19-06, 06:22 PM
I've googled around and found what look like 2 possibilities (neither cheap!)--
Shimano XTR M952 & XT M750 48t, 110mm, Chainring (and there's a 36t to go with it)
46t and 36t rings from T.A., a French company (the appeal of this one is that Harris Cyclery webpage says "TA Chainrings are made in France, very high quality, with shift-assist pins and ramps," whereas the Shimano one only mentions pins, not ramps.)
Does anyone have experience with these two types of chainrings? Also, do I have to worry about compatibility w/ chain? I have a sram chain, but could probably change it if necessary.
01-20-06, 04:00 AM
There is a lot of info on TA chainrings and compatability at
01-20-06, 05:40 AM
Many thanks to all who responded--I continue to be astounded at the helpfulness wealth of information available thru this forum. I'm about to place an order for the Shimano chainrings-- I only wonder what the "XTR and XT M750" refers to, and hope they'll be compatible . . . I'll read the Peter White info first, tho.
01-20-06, 06:15 AM
110 BCD rings are common and easy to come by. I usually go to eBay first for something like this. I've got an XTR 5-bolt 110 BCD large chainring, 46t, sitting around. (Little wear, but I replaced it with a 50t on my triple.) PM me if you're interested.
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