Bicycle Mechanics - Dura Ace triple- different chain-rings
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09-04-07, 03:53 AM
The Japanese one size fits all model is too restrictive for me.
I wish to replace the small and middle chain-ring with , say, a 34 and a 44 tooth ring. Or a 36 and and 46.
The gap from middle to big chain-ring is is too big for me, and this change would give me small jumps at the 20 to 22 mph range for me.
Shimano only has one size for the small and middle chain-ring on the Dura Ace triple. Does anyone know of someone who makes chain-rings that would fit?
09-04-07, 07:13 AM
Dura Ace triple cranks, both the 9-speed version (FC-7703) and 10-speed (FC-7803) do not have separate mounting bosses on the crank arm for the granny ring. The granny is mounted to tabs on the middle ring with a non-standard bolt circle of 92 mm. So the only granny ring available in this BCD is a 30T and the only middle ring equipped with the required mounting tabs is a 39T.
If you want to mix-and-match non-stock chainring sizes you will have to get an Ultegra or 105 triple crank as they have the much more common 74 mm bcd for the granny and a normally configured middle ring so you have a wider choice of chainrings.
09-04-07, 07:45 AM
This might work, http://sheldonbrown.com/harris/chainrings/130.html
looks like a 46/36 set would be $85.
Do not try to mix-and match on a DA triple.
The middle ring is very thick. With a different ring the teeth would be offset, screwing up shifting.
The little ring has a non-standard mount.
The ramp pattern is unique - a 'D' pattern.
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