Double specific chainset won't work with my old shifter. What now?

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  • Double specific chainset won't work with my old shifter. What now?
  • Just a clarity question to start with. Did you fit the crankset right to get the chainline? I just fitted a GXP Stylo 3.3 set and had to put both spacers on the non-drive side to pull it in enough to get my old mech to reach the outer ring.

    It shouldn’t be a problem. You need to use the first 2 positions on the shifter (granny and middle) and might need to leave the cable a bit slack on the small chainring.

    awh
    Member

    Guess shimano have moved the position of the rings on the cranks

    I thought the bike manufacturers specifically asked Shimano not to do this as they didn’t want even more standards. So a Shimano double uses the granny and middle positions. Maybe someone can confirm this.

    scud
    Member

    The new XT shifters have a small switch to change between double and triple ring set-ups.

    mudmonster
    Member

    My new xt double chainset wont work with my old triple shifter. Guess shimano have moved the position of the rings on the cranks. So now I need a shifter that pulls the right amount of cable. Which one do I need? Only the sram shifters seem to be double specific. Will all 10 speed shimano shifters work?

    Premier Icon njee20
    Subscriber

    The new XT shifters have a small switch to change between double and triple ring set-ups.

    As do the XTRs, I know when mine was on the ‘3x’ setting the shifting was crap, switch to the ‘2x’ setting and it was perfect. Suggests they’ve messed around with it somehow!

    Premier Icon speaker2animals
    Subscriber

    In what way do the old shifters not work with the new chainset? Over shift/under shift? Have you reset the end stops on your mech? BTW is there a double and triple specific front mech now? I’d have thought that a mech for a double could have a slightly smaller plate to plate dimension?

    mudmonster
    Member

    Yes should have made it clear that I had a double setup before with a xt triple chainset 22/36 rings and a slx mech with the shorter cage. Shifting was perfect. Got 73mm bb shell so got one spacer on the driveside. Small switch on the shifter is what I needed to know 😀

    mudmonster
    Member

    I think my front mech is double specific. I’m normally good with gears but there is no way I can get this to work.

    Are you going from 22/36 to26/38 or 28/40? afaik, the chainline IS different and the front mech probably won’t work then. The SLX double mech is meant for chainrings in the inner/middle position and on the xt doubles the chainline is further out. The cage profile won’t be correct for the rings anyway, although shouldn’t be too far off.

    I could quite possibly be wrong here!

    Premier Icon tomhoward
    Subscriber

    I’m running a 2×10 front mech on a 3×9 setup (xt m780 mech, xtr m970 shifters) and it works fine after a bit of tuning, but suprisingly little swearing.

    The 780 double mech will be meant for the wider chainline and bigger chainrings than the SLX one.. So it’s not so different from the 3x mech as the SLX.

    mudmonster
    Member

    Took the rings off and replaced them with the 22/36 rings. They must have changed the distance between the rings on the double version. It either rubs against the cage or drops off the chainrings. If I’d have bought a 10 speed triple it should have worked.

    Premier Icon speaker2animals
    Subscriber

    According to Shimano XT website the Chainline for the current triple is 50mm whereas for the double crank it is 48.8mm.

    I assume that this is a measurement from the centreline of the BB shell to a notional centre of the rings (so on a triple it would be where the middle ring lies, on a double I imagine a line between the two rings)?

    Just had a look at Sheldon Brown and my assumptions are correct. However it looks to be a minefield depending on frame type and crank being used.

    You say it either rubs on cage or drops off rings. On which side (ie rubbing on Large ring/dropping off little)? I’m not being condescending or don’t mean to be. Have you adjusted the end stop screws? Is the outer mech plate as close as possible to the large ring (1-2mm I think is recommended).

Viewing 14 posts - 1 through 14 (of 14 total)

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