Bicycle Mechanics - smallest chainring on compact cranks?

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tblendell
05-12-06, 02:02 PM
i'm going to do some touring on my cross bike. right now i have a 36 as my smallest chainring on my truvativ elita compact cranks.
is a 34 the smallest i can switch it out with?
also...will i need to readjust the derailleurs? i am NOT a mechanic but i'm sure i could manage just the swap out with the chainring. i think.
thanks!
troy

roadfix
05-12-06, 04:20 PM
What cassette are you running now? Perhaps you can get a more noticable difference by swapping to a large cogged cassette rather than swapping rings. 36 to 34 ain't much of a diff.....:)
HillRider
05-12-06, 04:47 PM
A 34T chainring is the smallest that will fit on the "standard" 110 mm bolt circle used on all current compact cranks. A 74 mm BCD, used for the granny rings of both road and compact triples, will go down to 24T.

Gonzo Bob
05-12-06, 05:08 PM
33T is the smallest that can go on 110mm BCD but might be tough to find. 34T is much more common. Normally you need to adjust FD height only when you change the big ring. But you may need to fidget with it a bit since you're increasing the difference between the two rings - especially if the FD outer cage is currently more than 2mm above the big ring.
LandLuger
05-12-06, 05:09 PM
33T is the smallest that can go on 110mm BCD but might be tough to find. 34T is much more common. Normally you need to adjust FD height only when you change the big ring. But you may need to fidget with it a bit since you're increasing the difference between the two rings - especially if the FD outer cage is currently more than 2mm above the big ring.

Harris Cyclery can get the 33T, but not worth the effort over the readily available 34T
DannoXYZ
05-12-06, 05:15 PM
Depending upon the crank-arm design, you may also need to file down the tips of the spiders to clear the 33t chainring...
fmw
05-12-06, 06:07 PM
I've tested both 34 and 36 tooth on the same bike. My preference is for 36 because it is useful for more than just climbing. I found the 34 tooth geared to low for me for anything but climbing. I can cruise along at 17 or 18mph on the 36 tooth and the middle portion of the cassette. Your reaction might be exactly the opposite, of course. It isn't expensive to find out. You can get a 34 tooth ring pretty cheaply on Ebay and stick it on there. Then you'll know.