Bit of a funny one this, but bear with me.
I've been running SunTour indexed thumbshifters (and wishbones) on various bikes for about 25 years, and have always been able to get at least 95%+ accurate indexing, whether it was 6-, 7- or 8-speed.
Until last week that is. The set-up was DX rear mech, 8-speed XC Pro thumbshifters, SRAM chain and SRAM 11-32 cassette (latter two modern and brand new). The indexing just wouldn't work. The main spring on the mech wasn't in great shape, so I swapped it out for an XT 8-speed. No joy, I was stumped.
Then I realised the variable: every other cassette or freewheel I'd ever used with the thumbshifters before was either SunTour or Shimano. Could it really be the SRAM cassette?
It appears so. Just swapped out the cassette for an HG-51 8-speed and everything's working fine on a quick test ride. Will check with some proper rides at the weekend.
Anyone else ever had similar issues?
I can only think that the different ramp shape on the SRAM cassette doesn't play well with the small amount of misalignment across the block you get with the SunTour shifters.
I've been running SunTour indexed thumbshifters (and wishbones) on various bikes for about 25 years, and have always been able to get at least 95%+ accurate indexing, whether it was 6-, 7- or 8-speed.
Until last week that is. The set-up was DX rear mech, 8-speed XC Pro thumbshifters, SRAM chain and SRAM 11-32 cassette (latter two modern and brand new). The indexing just wouldn't work. The main spring on the mech wasn't in great shape, so I swapped it out for an XT 8-speed. No joy, I was stumped.
Then I realised the variable: every other cassette or freewheel I'd ever used with the thumbshifters before was either SunTour or Shimano. Could it really be the SRAM cassette?
It appears so. Just swapped out the cassette for an HG-51 8-speed and everything's working fine on a quick test ride. Will check with some proper rides at the weekend.
Anyone else ever had similar issues?
I can only think that the different ramp shape on the SRAM cassette doesn't play well with the small amount of misalignment across the block you get with the SunTour shifters.