Spark 2013 and Xtr Incompatibility

eimart
eimart Posts: 52
edited April 2013 in MTB workshop & tech
Hello my friends,

I'm having a big problem with my new Scott Spark 900 RC 2013. I bought only the Frame and I bought a "Shimano XTR M985 Crankset 175mm, 30/42T" to use on it. The problem was that when i mounted it on the frame i realized that the space between the Outer rings (42 teeth) and the frame was too small, and due to the fact of being a Full Suspension frame, it was dangerously close to the rear part of the frame, with the risk of scratching and cracking the frame..
Then trying to solve this, i changed the crankset for a Shimano "XTR M985 Crankset 175mm, 28/40T". I thought that 2 teeth less is going to be enought to clear the space between frame and crankset.
But the last xc race that i raced, when i finished the race i realized that the 40T outer ring wasnt enought, the frame was scratched, check the photos, luckly it was not cracked.
Im writing here to check if someone have a suggestion for me to solve this, I was thinking about:

Option 1 - Use some BB spacers, but i dont know if i have space to use 2 spacers more. If i dont have space for spacers ill have to go with option 2.

Option 2 - Buy a Shimano XTR M980 26/38T and replace my M985 Crankset. But i am using a Shimano XTR M986 Shadow Plus SGS 10sp Rear Der. (Long Cage) , with a 11-36 Xtr Cassete. I dont know if this LONG Cage Rear Der. is going to work nice with this new 26/38T Crankset. Can anyone please help me ?

Photo of the scratches caused by the outer ring on the frame:

dsc09763qg.th.jpg

Comments

  • eimart
    eimart Posts: 52
    More photos:

    dsc09775e.th.jpg

    dsc09774yb.th.jpg

    dsc09773f.th.jpg

    dsc09772yh.th.jpg

    dsc09771oh.th.jpg

    dsc09770pd.th.jpg

    dsc09769j.th.jpg

    dsc09768i.th.jpg

    dsc09767s.th.jpg

    dsc09766d.th.jpg

    dsc09765al.th.jpg
  • eimart
    eimart Posts: 52
    dsc09764ta.th.jpg

    dsc09763qg.th.jpg

    dsc09762p.th.jpg
  • njee20
    njee20 Posts: 9,613
    That looks to have bags of clearance on the 40t? Is something happening when you compress the shock?

    The stock bike comes with an XX with a 42t outer, and the q-factor's no narrower IIRC, suggests something's up.
  • nicklouse
    nicklouse Posts: 50,675
    ok what BB and fitting? (width etc.... or)
    who fitted it?
    what combo of spacers etc
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • njee20
    njee20 Posts: 9,613
    PF30 on those, so no spacers IIRC, that was my first thought.
  • nicklouse
    nicklouse Posts: 50,675
    njee20 wrote:
    PF30 on those, so no spacers IIRC, that was my first thought.
    hence the question.

    it should be PF but is it?
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • eimart
    eimart Posts: 52
    Guys i am using a "Shimano BB-91A Press Fit Bottom Bracket Mountain" and was thinking about buying 4x "SHIMANO BB91-41A BOTTOM BRACKET SPACER 2.5MM"
  • eimart
    eimart Posts: 52
    njee20 wrote:
    That looks to have bags of clearance on the 40t? Is something happening when you compress the shock?

    The stock bike comes with an XX with a 42t outer, and the q-factor's no narrower IIRC, suggests something's up.

    Hi,

    Nothing unusual is hapenning when i compress the shock. The Spark 900 RC Stock comes with a SRAM XX GXP PF 39Ax26A T
  • eimart
    eimart Posts: 52
    nicklouse wrote:
    ok what BB and fitting? (width etc.... or)
    who fitted it?
    what combo of spacers etc

    I am using a "Shimano BB-91A Press Fit Bottom Bracket Mountain"
    Fitted by a mechanic in Alex Bycycle Pro Shop
    And the spacer that i want to buy are: "SHIMANO BB91-41A BOTTOM BRACKET SPACER 2.5MM" x 4
    But i dont know if i will have space to use them.
  • eimart
    eimart Posts: 52
    Ive contacted the bike shop that build my bike and here is the answer:
    "Check that all bolt on the chainstay/seatstays are tight as you are flexing the frame too much. It does not seem that the chainrings are doing that."
    But i dont know if this is the problem
  • The Rookie
    The Rookie Posts: 27,812
    Well there is static clearance as shown in your photo's, the contact point (assuming there was contactand not debris carried up or chain suck) is quite close to the pivot, so that is a big angular movement, so certainly worth checking.
    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.
  • eimart
    eimart Posts: 52
    The Beginner, what do you recommend ?
  • The Rookie
    The Rookie Posts: 27,812
    Checking all the pivot points (bushes and bearings) for play, a quick bolt check as well, make sure they are tight!
    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.
  • eimart
    eimart Posts: 52
    Guys,
    ive discovered something that i didnt realized before.
    I am using a XTR M985-E Front Derailleur, according to Shimano website it is for 40-44T Chainrings.
    I think that the correct one to use is the M985-E2, that according to shimano specs website is for 38T.
    Is it possible that this is the cause of the problem ??

    Thanks,

Categories