# XR650R Gearing Question

4 replies to this topic
• # Gray

Posted January 04, 2007 - 05:55 PM

I have a new 2006 XR650R with factory 14/48 gearing and am considering changing front sproket to 13 tooth. Is a 13 tooth too hard on the chain? If not then which brand sproket would make a worthy replacement? I have looked at the Sidewinder but I don't know much about the company. Any suggestions? Thanks, Greg

• # frankstr

Posted January 04, 2007 - 07:11 PM

Welcome to Thumpertalk, Gray,
I like the Ironman sprockets myself , They have been on my bike over a year now.
I have 14/51 gearing...

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• # 1stgear

Posted January 04, 2007 - 08:26 PM

I run 13/51 ironman sprockets, DID x-ring chain, two links longer than stock with a Teraflex tire, white bros pipe. Works great. Guys I rode with last weekend said the bike was shooting rocks the size of baseballs at them.

• # motopsycho650

Posted January 07, 2007 - 05:07 AM

I run 13/51 ironman sprockets, DID x-ring chain, two links longer than stock with a Teraflex tire, white bros pipe. Works great. Guys I rode with last weekend said the bike was shooting rocks the size of baseballs at them.

My cousin bought a rear ironman sprocket for his WR450. It has been on his bike for maybe 1000 off-road miles, and has more visible wear than my stock Sunstar sprocket with 3000 miles on it on my XR650R.

I don't know about if a 13T front will hurt the chain, but stick with STEEL Sunstar sprockets.

P.S. While on the subject. Here's a handy equation for figuring speed adjustments with different gearing. Take the larger sprocket size, and divide it by the smaller. I'm still stock, so I'll use 14-48.

48/14 = 3.43 gearing (I.E. the counter-shaft sprocket spins 3.43 times per rotation of the drive sprocket).

48/13 = 3.69 gearing.

Ok, for me, my top speed is 95 Mph with 14-48, so we'll set the equation up like this:

A=Current Gearing, B=New Gearing, C=Old Top Speed, X=New Top Speed
(A * C) / B = X
(3.43 * 95) / 3.69 = X

To find the value of X, multiply 95 * 3.43 (= 325.85). Now take the product, and divide it by the new gear ratio. (325.85 / 3.69 = 88.3)

With 13-48 gearing, you new top speed will be around 88 Mph.

• # Gray

Posted January 08, 2007 - 05:20 PM

Man that is too cool. You are way smarter than I am. I appreciate the equation and the valuable input. I will use a Sunstar steel 13 tooth front that I believe will give me what I am looking for.
Thanks, Greg.

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