Rear mech compatibility

manglier Posts: 1,231
edited December 2010 in Workshop
I am finding a 50/34, 12-27 (Sram Rival) setup does not give me low enough gearing for my creaky old knees. If I swapped out the 50 for a 46 large ring would I be able to fit the new Sram Apex 11-32 cassette without having to get a longer rear mech?


  • Largest Cog: 28 teeth
    Chain Wrap Capacity: 31 teeth

    so no.
  • manglier
    manglier Posts: 1,231
    Not quite sure I understood your response ride_whenever.
    Got the bike fitted with 50/34, 11-28 which gives chain wrap as 33, the same as 46/34, 11-32. Please tell me where I am going wrong.
  • nicklouse
    nicklouse Posts: 50,675
    the issues is the largest cog size.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • Monty Dog
    Monty Dog Posts: 20,614
    You need the Apex rear mech for anything bigger than a 28 sprocket otherwise the upper jockey wheel hits the cassette - its down to physical incompatibility rather than the 'capacity' of the gear system - the distance to the upper jockey wheel is bigger on the Apex mech, akin to an MTB gear mech.
    Make mine an Italian, with Campagnolo on the side..