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2x10 question

mxhmxh Posts: 51
edited April 2014 in MTB workshop & tech
I was out riding the other day with a group, and one of the guys was on a Specialized Stumpjumper (2012 I think) which was running 2x10 with a mid-cage SRAM X0 rear derailleur. He was having a few problems with shifting gears, so we turned it over and had a look to see what was wrong.

When running in the big ring at the front, he was able to use the big ring on the rear OK. However, running on the smaller front ring, he could only run the 6 biggest gears on the rear - any of the smaller ones resulted in a loose chain as the RD wasn't able to take up the slack, and therefore the RD was just getting caught up in the cassette.

When I pointed out that this was wrong, he assured me that a) this was how it was bought from new and b) a bike shop mechanic had told him that this was correct, and that 2x10 isn't designed to work on the all available ratios.

Not knowing the guy that well, I wasn't going to push the issue at all, but I'm still confused as to how it left Specialized in this state (allegedly) and why a mechanic would say it's correct. I reckon the RD could have handled one less link in the chain (on big to big) but there's no way that would take out the amount of slack needed to make it run OK on the small to small cogs.

I've not personally run SRAM gear (currently running Shimano XT 2x10 myself, with a full range of usable gears!) so maybe I'm wrong about it, and this is how it's supposed to be, although somehow I doubt it. Any ideas?

Posts

  • The RookieThe Rookie Posts: 27,748
    Sonds like the chain is too long, however the chain may need to allow for length growth on an FS (You don't mention which stumpy) and that may mean a mid cage which has the right capacity on paper can't manage the growth as well.
  • mxhmxh Posts: 51
    Yes - it does sound like the chain is too long - but as mentioned, you'd only get away with removing one link - any more and the chain wouldn't stretch over the 'big to big' range. And one link less isn't going to remove enough slack to allow the 'small to small' setup to work.

    Not sure I'd agree with the suspension theory (yes, it is a FSR) - can't believe Specialized would 'forget' to test that.

    So it seems to me that this is either correct for a SRAM setup (which I find hard to believe) or someone's put a mid cage RD on by mistake and it should be a long cage.

    Anyone got a 2x10 SRAM setup who'd like to check to see whether they get the full range?
  • 2x10 on a Boardman hardtail , medium x9 mech , chain correct length using big front /big rear bypassing derailleur then snap link. All combinations useable with no rub.
  • The RookieThe Rookie Posts: 27,748
    You can't compare an HT to an FS that may or may not have significant chain growth.....

    The mech may have the capacity 'on paper' but if chain growth through suspension travel means it needs 2-3 more pairs of links then the mech may not be able to cope, only way is to check the chain is the right length PROPERLY.
  • 2x102x10 Posts: 79
    I have a 2007 stumpjumper with SRAM 2 x 10 and a long cage. every gear every time, my son has a 2010 with the same set up, works perfectly. I would guess a set up problem? too long a chain or perhaps it needs the long cage?
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