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1x10 chain ring size

andylitandylit Posts: 14
edited May 2013 in MTB workshop & tech

i am currently waiting for my new bike to turn up and i am planning on changing it to 1x10 (my current bike is 1x9)

however, since ordering the bike i have realised it has a 120 BCD on the cranks which limits my chain ring size to a minimum of 36 teeth. is this going to be too big? cassette is 11-36



  • Chunkers1980Chunkers1980 Posts: 8,035
    If the wheel sizes are the same then try 32/32 or whatever you have to make 1:1 and see?
  • andylitandylit Posts: 14
    thanks, will need to have a look at the cassette size on my current bike.

    any more views from others would be appreciated too
  • warpcowwarpcow Posts: 1,448
    Only you can know if it'll be too big. It'd be on the upper limit of what I'd push; 34t and 11-36 cassette works well allround for me.

    If the cranks are nicer SRAM (guessing since they're 120mm BCD) you could use a direct-mount ring.
  • njee20njee20 Posts: 9,613
    I run a 36t single ring (with 11-36 block) wouldn't want to go smaller. Not for everyone though.
  • andylitandylit Posts: 14
    the cranks are only X5 so i think the option of direct mount is out. dont want to upgrade the cranks yet
  • andylitandylit Posts: 14
    also, having just had a look at the cranks online i think there may be clearance issues with chain guides. anyone know is this would be true
  • lostboysaintlostboysaint Posts: 4,250
    njee20 wrote:
    I run a 36t single ring (with 11-36 block) wouldn't want to go smaller. Not for everyone though.

    Not as fit as Njee so have a 34 on a 11-34 cassette!!
    Trail fun - Transition Bandit
    Road - Wilier Izoard Centaur/Cube Agree C62 Disc
    Allround - Cotic Solaris
  • andylitandylit Posts: 14
    in theory though, if you are running a 34 with 11-34 and Njee is running a 36 with 11-36, in the lowest gear the ratio is the same at 1:1 i know the other ratios will be different but when grinding up a hill the lowest gear is the one that matters
  • MaroMaro Posts: 226
    I currently use a 38 with (9speed) 11-32. It's hard work on steep or very long climbs but certainly do-able.
    Bird Aeris. DMR Trailstar. Spesh Rockhopper pub bike.
  • njee20njee20 Posts: 9,613
    That's pretty tall, I know I couldn't do that!
  • andylitandylit Posts: 14
    that is tall. think i may give the 36t a try. but i am a little concerned about the chain guide clearance on the 120BCD cranks
  • njee20njee20 Posts: 9,613
    Yes it could be an issue - most chain guides will be optimised to sit in the middle ring position of a triple, whereas yours will be in the outer position of a double and thus a couple of mm further out. I've got an E.13 XCX guide to fit to mine, but may well have the same issues (XTR M985 double), in which case I've got a home made guide using a Superstar cage and a DMR seat tube mount.
  • andylitandylit Posts: 14
    Thing i may leave it as 2x10 and maybe put a 2x chain device on it. and possibly reduce the 42 outer ring to a 39. would i need to do anything to the front derailleur if i reduce the size of the outer ring?
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