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New crankset doesnt fit? wtf?

richardjilesrichardjiles Posts: 137
edited July 2012 in MTB workshop & tech
So I just got my new front chainwheel crankset piece, I put it on and wtf? it goes way too far on, so that my front deraleur will never get it on first gear... man wtf? when ordering the part I made sure all the chainrings were the same size, but I decided to buy a smaller crankarm size, went from 175 to 170, will that make the difference? I dont think so because others talk about buying new cranks with smaller size

UPDATE:
I don't know the previous Crankset, however the new one is shimano altuls
Right, just took readings from my current bottom bracket, its 68 x 110.5
so my new one should be 68 x something, now as long as its altus compatible does it matter?

Posts

  • nicklousenicklouse Posts: 50,675 Lives Here
    err yes great. what do you want us to do?

    from what to what?
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • angry_birdangry_bird Posts: 3,785
    Like Nick says how can we help based on that. What model do you have now? What model did you have? What size BB do you have? Got enough BB spacers in?
  • nicklousenicklouse Posts: 50,675 Lives Here
    Angry Bird wrote:
    Like Nick says how can we help based on that. What model do you have now? What model did you have? What size BB do you have? Got enough BB spacers in?
    Does it even use spacers!
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • crispy1980crispy1980 Posts: 310
    probs done what i did and ordered a crank set without realising that it has to be matched to the axle length of the bb. sounds like yours isnt and is therefore sitting the chain rings too far in, causing said problems.
  • richardjilesrichardjiles Posts: 137
    k so how do i go about getting a new bb? its square tapered
  • richardjilesrichardjiles Posts: 137
    I don't know the previous Crankset, however the new one is shimano altuls
    Right, just took readings from my current bottom bracket, its 68 x 110.5
    so my new one should be 68 x something, now as long as its altus compatible does it matter?
  • nicklousenicklouse Posts: 50,675 Lives Here
    Part numbers?
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • richardjilesrichardjiles Posts: 137
    New cranks - FC-M311
    Old cranks - FC-MC19
    current but not fitting bb - (UNKOWN) but its 68 x 110.5
  • nicklousenicklouse Posts: 50,675 Lives Here
    You need a 123mm axel.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • richardjilesrichardjiles Posts: 137
    nicklouse wrote:
    You need a 123mm axel.
    Thanks!!!
    but how did you manage to figure this out?
  • The RookieThe Rookie Posts: 27,777
    By looking at the parts technical documents on the Shimano website.

    While 123mm is what you want, some list 122 or 122.5 and they would be fine (0.5mm or 0.25mm isn't going to make a meaningful difference!)
    Current steed - Whyte T129, 2013 frame, mongrel Revelations, Giant dropper, Stans S1 wheelset. 12, Magura Trail Sport brakes, 1x11. 12.8Kg
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