Shimano middle chainring same as a small double?
04-13-09, 07:49 AM
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Shimano middle chainring same as a small double?
I'm looking at swapping out my 30T granny and 42T middle chainrings for something smaller.
I'm looking at a 39T 130bcd Shimano chainring on Evilbay. I'm not sure if it is for a double or a triple.
Is there a difference? If the chainring was off a double will it matter at all if I use it as a middle ring?
I'm using friction shifting on the front, if that makes any difference.
I'm looking at a 39T 130bcd Shimano chainring on Evilbay. I'm not sure if it is for a double or a triple.
Is there a difference? If the chainring was off a double will it matter at all if I use it as a middle ring?
I'm using friction shifting on the front, if that makes any difference.
04-13-09, 07:59 AM
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The 39t you're looking at looks like it is designed for a double crank. Modern middle chainrings designed for a triple crank will have pins and/or ramps and profiled teeth to help with shifting from the granny into the middle ring.
If so, the chainring will still function okay in a triple setup, but shifting from granny to middle won't be quite as snappy as a middle chainring with pins or whatever. This may be a problem for you if you have Shimano STI-Triple shifting, definitely not a problem if you have down-tube or bar-end shifters.
If so, the chainring will still function okay in a triple setup, but shifting from granny to middle won't be quite as snappy as a middle chainring with pins or whatever. This may be a problem for you if you have Shimano STI-Triple shifting, definitely not a problem if you have down-tube or bar-end shifters.
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"c" is not a unit that measures tire width
"c" is not a unit that measures tire width
04-13-09, 08:51 AM
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yeah, I tried usind a double small ring on a middle triple set up. shifting sucked, get the correct part.
04-13-09, 08:57 AM
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Shifting may suck if you're using STI triple shifters, particularly Sora (because there's less room for adjustment).
If you're using down-tube or bar-end (or, for that matter, Campy Ergopower), you'll have plenty of room for adjustment to overshift on the upshift from granny to middle ring.
And besides, shifting from granny ring to middle ring is a relatively rare shift, compared to shifting between middle and large ring. So it doesn't hurt that often.
If you're using down-tube or bar-end (or, for that matter, Campy Ergopower), you'll have plenty of room for adjustment to overshift on the upshift from granny to middle ring.
And besides, shifting from granny ring to middle ring is a relatively rare shift, compared to shifting between middle and large ring. So it doesn't hurt that often.
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"c" is not a unit that measures tire width
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04-13-09, 11:22 AM
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04-13-09, 11:42 AM
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"c" is not a unit that measures tire width
"c" is not a unit that measures tire width
04-13-09, 05:13 PM
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Thanks for the advice. I'm using bar-end shifters, so if the chainring goes cheap enough I might suck it and see.
