I am looking to upgrade my drivetrain, essentially moving from road (Ultegra and 105) to XT mountain. I'd like to avoid replacing my rear wheel if possible though.

I've read conflicting things about whether the hub spacing between road and mountain is compatible. Can anyone answer definitively?

  • How are you changing from a road groupset to a mountain one? Are you replacing drop bars with flat bars? Are you planning to keep parts of the road groupset? Commented Sep 26, 2018 at 16:32
  • I'm replacing the cassette, the derailleurs, the crankset and the BB. I am keeping the brakeset.
    – dylanmac
    Commented Sep 26, 2018 at 17:16
  • What are you doing with the brake/shifter units? 9 speed shifters ain't gonna work with an 11 speed derailleur and cassette. Commented Sep 26, 2018 at 17:24
  • 1
    I should have mentioned that I am adding the Shimano 11 speed trigger shifters as well. or maybe even the xshifter setup.
    – dylanmac
    Commented Sep 26, 2018 at 20:04
  • You are gonna want to check the mountain brake levers have the correct pull ratio for the road brake you presumably have. Commented Sep 26, 2018 at 21:44

1 Answer 1


Changing from a 9 speed road to 11 speed mountain raises many, many questions, but answering your specific query:

An 11 speed mountain cassette will fit on a '9 speed' hub. The freehub body width used is the same for mountain 11 speed and below and road 10 speed and below. Road 11 speed cassettes generally requires a slightly wider freehub body. The mountain 11 speed cassette will fit because the larger sprockets can overhang the hub and spokes a little.

  • Do I need a spacer?
    – dylanmac
    Commented Sep 26, 2018 at 17:17
  • @dylanmac to get the cassette on the hub, no. Are you thinking about getting the chainline right? Commented Sep 26, 2018 at 18:02
  • No I was more concerned about the cassette sitting on the hub without play.
    – dylanmac
    Commented Sep 26, 2018 at 20:04

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