Rear sprocket question?

5 replies to this topic
  • toofast2

Posted March 26, 2008 - 04:22 AM


Hi,'06' YZ450F,I have stock sprokets(13/49) i would like to go smaller in rear
to a 47t without changing the length of the stock chain,would I have enough adjustment to get the proper chain slack if I went with a 47t??? THX

  • grayracer513

Posted March 26, 2008 - 06:09 AM


If your chain is in good condition, yes.

  • toofast2

Posted March 27, 2008 - 04:26 AM


If your chain is in good condition, yes.

Thanks Grey for the reply,chain is fairly new Regina o-ring,stock lenght,do you think if I put a 37,I'll still have room to adjust when chain starts to stretch? THX

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  • grayracer513

Posted March 27, 2008 - 07:07 AM


I doubt it. The wheel should move about 1/4 the difference in sprocket circumference. Your sprockets are for a 5/8" pitch chain, so the circumference can be calculated as the number of teeth times .625. Since there is a 2 tooth difference between a 49 and a 47, the difference in circumference is 2 x .625 = 1.25. The chain wraps over only just a little over half of the sprocket, so only half the difference has any effect. Since the difference in length is distributed to two lengths of chain (the upper and lower run) that meet each other, each length of chain is longer by half of that. So, 1.25/4 = .3125" (5/16") that the axle must move.

A simpler way to arrive at this is just to take half the number of teeth difference times the pitch, or 2/4 = 0.5 x .625 = .3125"

With a 37, however, there is a 12 tooth difference, so that means the wheel would need to move about 1.875" (3 x .625).

  • toofast2

Posted March 27, 2008 - 11:42 AM


Gray,thats the reply I like to see(very specific)...except I made a typo:crazy: I meant 47 tooth,not 37 tooth...I want to go to 47,from
49...just need to know if there will be room to adjust with new chain,
and when chain gets stretched...sorry about the TYPO:excuseme:

  • grayracer513

Posted March 27, 2008 - 04:47 PM


The 47 should work. I kind of wondered where you were going to get a 37.

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