I have a Kona Explosif from 1997 with the factory sugino mighty 900 crranks and chainrings installed. I wanted to change the cranks as the left hand arm is badly threaded. Without checking I purchased a pair of Deore XT M739 arms but I don’t think they can work with the existing chainrings as the XT cranks have what looks like a 5 arm spider? What can I do? I am right that they are not compatible? Any help appreciated.
Question about cranks
- Thread starter redfour
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gtturbo
Senior Retro Guru
Re:
From a quick google it looks like the Sugino cranks are 5 bolt, the 5th bolt is hidden behind the crank arm. Now if that is true then the next thing to check is the BCD/PCD (Bolt circle diameter or Pitch circle diameter) of the rings, its the distance between the chainring bolt holes. Theres a few different sizes but I think off the top of my head you could be in luck. Best bet is to strip the rings from the old crank arm and then line them up on the XT arms. If the bolt holes all line up you are good to go. You may need 1 extra rear part of a chainring bolt as the image I found of the 900's would suggest there is a thread on the back of the crank arm which it screws into which the XT's won't have.
From a quick google it looks like the Sugino cranks are 5 bolt, the 5th bolt is hidden behind the crank arm. Now if that is true then the next thing to check is the BCD/PCD (Bolt circle diameter or Pitch circle diameter) of the rings, its the distance between the chainring bolt holes. Theres a few different sizes but I think off the top of my head you could be in luck. Best bet is to strip the rings from the old crank arm and then line them up on the XT arms. If the bolt holes all line up you are good to go. You may need 1 extra rear part of a chainring bolt as the image I found of the 900's would suggest there is a thread on the back of the crank arm which it screws into which the XT's won't have.
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iirc ALSO you need to flip the ring 180degree, not just a slight rotation. i.e. the 'tags' are now opposite the crank arm.
This keeps the shifting points and larger teeth in the correct place, of course that depends on the rings, but line up as the would normally be fit, and then work out which rotation keeps the ramping correct.
This keeps the shifting points and larger teeth in the correct place, of course that depends on the rings, but line up as the would normally be fit, and then work out which rotation keeps the ramping correct.
