Bicycle Mechanics - SRAM Shifter Compatibility
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08-28-11, 01:05 PM
My Trek Mtn bike came originally with SRAM 400 (7 speed) shifters. I recently purchased a set of SRAM 3.0 (7 speed) shifters. I can not get the new rear derailleur to work properly. I would have thought the new shifters would be compatible. I can shift from the lowest to highest gear, but I skip one gear in between. When I'm on the largest cog, the shifter is on #6 rather than top gear #7. I measured the amount play on both shifters and the new 3.0 shifters have more play than the older 400 shifters. Any help would be appreciated :)
SRAM has two lines of shifters with different actuation ratios. One is Simano compatible, the other require a SRAM derailer with a matching actuation ratio to index properly.
400s are Shimano compatible, which means 2:1 cable pull. 3.0s are SRAM compatible, which means 1:1 cable pull. You must have a matching shifter and RD.
08-28-11, 03:27 PM
Yellowdog: My understanding is that SRAM shifters with names (Attack, TRX) are compatible with Shimano 2:1 pull; the ones with numbers (X3, X7) are compatible with SRAM 1:1 pull derailleurs.
08-28-11, 04:02 PM
I acquired this bike as parts, and all I had was a SRAM 3.0 shifter set. I found out it - like yourself - that it wouldn't work right, sometimes skipping a gear for each click.
I modified the 7-speed shifter by dremeling extra detents into the inside ring. Being I needed a 2:1 ratio, adding a detent between each of the stock detents gave me the clicks I needed. Thing worked like a champ. Alot of work, but functional.
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