Can XX really shift under load??

sminne
sminne Posts: 6
edited October 2012 in MTB workshop & tech
I just acquired a 2nd hand 2012 XX system on a stumpjumper hardtail and am not impressed with the front shifting. It seems that it will barley up shift under any load. This is quite contrary to what SRAM advertizes. Have others found the front upshifting under load to be satisfactory? Any ideas what might be wrong with my system?
Thanks in advance,
Steve

Comments

  • Chunkers1980
    Chunkers1980 Posts: 8,035
    Is it setup correctly?

    What do you mean by load?
  • njee20
    njee20 Posts: 9,613
    How are the chainrings? My XX big ring lasted no time at all, and shifting suffered with it. When everything was new it did shift well, but to be honest I'd not say it shifted any better under load than XTR. Not used anything else to compare for years!
  • sminne
    sminne Posts: 6
    Thanks. I believe it is set up correctly, and your question of what I believe to be load is one I also struggle with. It shifts very well on all flats and downhills (of course).

    However, if for example when I am about to crest a climb (10% grade max) and want to upshift to prepare for the decent, it shifts OK if I simultaneously up-shift (to easier gearing) the rear by 3 rings, while at the same time up-shifting (to harder gearing.) the front. But if I just try to shift only the front in this situation (10% grade while maintaining speed or trying to accelerate) it will just grind the chain again the side of the larger chainring.

    I do believe I have it set up correctly. . .however maybe not. I don't really know because I don't have a good reference for XX. I do know its MUCH worse than my 2007 Stumpjumper Comp triple (Stylo?) - which rocks in this regard. On the other hand, that is a triple so its pretty easy to force the chain to the middle ring in these situations (ie no upper stop limiting the shift).

    Things I have checked:
    Brand new crank and rings (XX w/ X Glide, 39/26 – no spacers installed with cranks)
    Brand new chain (1091-R)
    >100mi on XX cogs (36/11)
    Front derailleur ~1mm from teeth, parallel to rings. Top limit set just short of pushing chain over
    Shifter cable adjusted tight when in the low ring
    XX shifter
    (Bottom bracket installed backwards, but the schematics show it symmetric so that should be OK).
    So. . .is it me or my rig???
    Thanks,
    Steve
  • bikaholic
    bikaholic Posts: 350
    I realise that this thread is about shifting under load but is shifting the same, worse or better when not under load?

    By not under load, I mean that you coast (whilst still turning the cranks) for up to half a revolution in order to finesse the chain into gear and then, once in gear, you apply load by putting the power down. So the sequence goes: shifter click, finesse chain, feel the gear change, put power down.

    The reason I ask you to do it this way is to see if you can get the timing right - it should be very fast.

    Likewise with shifting under load: it might just be a question of timing.
  • paul.skibum
    paul.skibum Posts: 4,068
    sminne wrote:
    Thanks. I believe it is set up correctly, and your question of what I believe to be load is one I also struggle with. It shifts very well on all flats and downhills (of course).

    However, if for example when I am about to crest a climb (10% grade max) and want to upshift to prepare for the decent, it shifts OK if I simultaneously up-shift (to easier gearing) the rear by 3 rings, while at the same time up-shifting (to harder gearing.) the front. But if I just try to shift only the front in this situation (10% grade while maintaining speed or trying to accelerate) it will just grind the chain again the side of the larger chainring.

    Sounds a bit like you might be torturing your drive train. If you can shift down 3 cogs on the rear it sounds like you might have the chain line a bit out of whack? I don't mean to sound like I am teaching granny to suck stuff but you are aware that you should use the little ring at the front with the the bigger ones at the back and not cross the two up too much?

    In a 2x10 set up I would expect to use the 4-5 biggest rears with the smaller front and visa versa witht he big front. I have no experience of XX bit I know that nothing I have used would take me hammering down on the pedal in an upshift, especially if its all crossed up.
    Closet jockey wheel pimp whore.
  • The Rookie
    The Rookie Posts: 27,812
    It sounds simple to me, I think your high stop is set too low, back the high stop off a bit and if you want faster shifts you keep thumb pressure on the shifter (moving the cage past where it will rest) letting go once it shifts. You shouldn't be shifting under full pedal load anyway if you want good component life!
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.

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