My old bike had an Exage FD with triple chainrings 28, 34, 40 (it's very flat where I live). I recently got a new bike with Alivio FD and 22, 32, 42 chainrings. Moving the old chainrings to the new bike, the Alivio derailleur won't shift cleanly because the geometry of the cage is different - it has to be set higher than optimum for the big chainring so that it clears the middle one. Clearly it's designed for the bigger difference in sizes. I can't fit the old Exage one because the seat post diameter is different.
What current FD would work well with these ratios? Or, if the answer is None, what is the minimum acceptable difference in number of teeth?
And, when buying a new FD, how is the clamp width specified - diameter or seat post, or circumference?
My wife's bike with 24-34-40 chainrings is using a Record triple FD without problem. I suspect that any FD intended for double chainrings would work, it's just that I didn't have a double FD with a 34.9mm clamp. The Deore XT FD that was installed with the original 26-36-48 chainrings wouldn't work with the 24-34-40 chainrings as the inside of the cage fouled the middle chainring unless the FD was raised about 1/2" above where it should be.
Nick
"Craig" <[email hidden]> wrote in message news:[email hidden]...
Quoted message said:
My old bike had an Exage FD with triple chainrings 28, 34, 40 (it's very flat where I live). I recently got a new bike with Alivio FD and 22, 32, 42 chainrings. Moving the old chainrings to the new bike, the Alivio derailleur won't shift cleanly because the geometry of the cage is different - it has to be set higher than optimum for the big chainring so that it clears the middle one. Clearly it's designed for the bigger difference in sizes. I can't fit the old Exage one because the seat post diameter is different.
I just set up my half step plus granny touring bike with a Shimano Sora double front derailleur. Chainrings of 45-42-20. Shifts OK. Cost was about $11.50 for the derailleur from Nashbar. Surprisingly the derailleur is able to handle the 25 tooth difference on the front without the chain dragging on the bottom of the cage when in the small cogs in back.
[email hidden] (Craig) wrote in message news:<[email hidden]>...
Quoted message said:
My old bike had an Exage FD with triple chainrings 28, 34, 40 (it's very flat where I live). I recently got a new bike with Alivio FD and 22, 32, 42 chainrings. Moving the old chainrings to the new bike, the Alivio derailleur won't shift cleanly because the geometry of the cage is different - it has to be set higher than optimum for the big chainring so that it clears the middle one. Clearly it's designed for the bigger difference in sizes. I can't fit the old Exage one because the seat post diameter is different.
What current FD would work well with these ratios? Or, if the answer is None, what is the minimum acceptable difference in number of teeth?
And, when buying a new FD, how is the clamp width specified - diameter or seat post, or circumference?
