XX Crank QF?

Printable View

  • 03-07-2010
    riding29
    XX Crank QF?
    Besides being able to have the same QF as your road bike, is there any reason to get the narrow 156? I've never been bothered by my XT cranks. Maybe I'm missing something?
  • 03-08-2010
    crewcabrob
    Hello,

    I could be wrong about this, but I believe that not all frames will accept the narrow 156 QF.

    I'm trying to figure out which QF to use on my 09 S-Works Stumpy FSR. My LBS says that I need something larger than the 156 for my frame.

    Anyone have additional information for either of us?

    Rob
  • 03-08-2010
    diveforblood
    The biggest advantage to the narrower q factor in my opinion is that you can more efficiently run the entire cassette range from either front chainring. The narrower stance on your pedals doesn't hurt things either in my opinion.

    As for compatibility sram has a pdf which explains how to measure your frame to determine which crank set you need. It can be found here

    http://www.sram.com/_media/techdocs/...ifications.pdf

    Hopefully this answers you guy's questions. I'm currently running the 166 q factor cranks and can tell you that they're amazing.
  • 03-13-2010
    Alta825
    if i have a bike with the '10 Noir crankset and there is decent clearance, will the 156mm version XX crank work? bike is a 29er hardtail - Felt Nine Team
  • 03-13-2010
    diveforblood
    I was running the 09 Noir's and had lots of clearance on my Titus but couldn't clear the 156's. The only way to really have a good idea though is to measure out the frame based on the SRAM tech doc. Clearance for the crank is mostly dependent upon your drive side chain stay.
  • 03-20-2010
    aussie_yeti
    the 156 and 166 q cranks both use the same chainline, so the ability to use the whole cassette while in the big ring doesn't change between q-factors. the only reason to run the narrower q-factor is if you like to pedal with your feet closer together.

    the q-factor on a truvativ noir crankset is 172mm. 172-156=16, 16/2=8. the arms are the same thickness between noir and xx therefore you must have 8mm of clearance between the inside of your noir crankarms and you chainstays for the 156 q xx cranks to be able to be installed. you'd then want a few more mm clearance to account for small amounts of flex in the crankarms/chainstays during riding otherwise you'll definitely get contact. i'd suggest you want at least 12mm between noir crankarm and chainstay to safely fit the 156 q xx crankset.
  • 03-22-2010
    riding29
    Quote:

    Originally Posted by aussie_yeti
    the only reason to run the narrower q-factor is if you like to pedal with your feet closer together.

    Does that provide any sort of advantage? Is it just for people with 29 inch waists?
  • 03-22-2010
    diveforblood
    My understanding is that you have better power transfer due to your feet being more inline with your knees, thus putting less lateral strain on them.