DatboyB

Hello, everyone, I am new to bike forums, but have been a reader and cycling enthusiast for a while.

I recently upgrade my old Gary Fisher mountain bike (shifters, brakes, wheels) and put on it 9-speed SRAM 7.0 shifters. I retained the original circa 1999 SRAM 5.0 rear derailleur and 8-speed cassette with the understanding from SRAM's FAQ that all 1:1 actuation items are compatible. When I went to the LBS to get a new chain, the tech said that the bike may never shift perfect because of the shifter/cassette mismatch and the narrower width of the chain for a 9-speed.

Before I went to the LBS, I had the shifters shifting up and down the full range; however, the 9-year old chain has some stuck links--the reason for the upgrade--which I suspected limited the smoothness, maybe I am wrong. My questions are:

Am I misinformed by the mechanic? Should I upgrade the cassette to 9-speed? If I do, is the 5.0 rear derailleur compatible?

Thanks for the input.

B

JiveTurkey

For rear indexing to work properly, the number of positions in the shifter must match the number of cogs in the cassette. The spacing is different: 8-speed SRAM is spaced 4.8mm between cogs, 9-speed is spaced 4.34mm. The 9-speed shifter will pull less cable than it needs to for the 8-speed cassette, so it might work for a few gears but probably not all 8. https://sheldonbrown.com/k7.html#spacing

As long as the cable pull ratio is the same, the rear derailleur doesn't really care how many gears you're running. In your case, both the 7.0 shifter and 5.0 RD adhere to the SRAM MTB 1:1 standard, so the combo will work fine once you put a SRAM/Shimano 9-speed cassette and chain on there.

DatboyB

Thanks, Jive.