shock/spring rate


2 replies to this topic
  • hellboy

Posted October 13, 2008 - 05:04 PM

#1

From what i under stand from race tech, yamaha put front springs for a 200lb rider and a back spring good for 180lb rider, i'm 210lbs their figures comes out to .476 front 5.5 rear. stock is .47 and 5.3 are these rates with their valving or am i missing something? the back shock comes in between sizes, i can go 5.4 or 5.6,i don't know what to order.(2008 450 motocross only)

Thanks for the help rob

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  • grayracer513

Posted October 13, 2008 - 06:40 PM

#2

Race Tech's info on their web site is wrong with regard to the rear spring rate on the '08, at least according to Yamaha (who may know something about it) Because of a linkage change in '08, the stock spring rate at the rear of the '08 is 5.5, not 5.3. (Ref: Yamaha Owner Service Manual, page 7-8)

To use their spring generator, I would do a work up on both an '06 and an '07 for your weight (without gear, for their site), and compare it to the stock rear spring rate. Apply the difference to the stock 5.5 rate on your bike. For example, if the recommendation is to go from the stock 5.3 on an '06 to a 5.5, then choose a 5.6 or 5.7 for yours.

The fork spring rates for all 3 years should come out very nearly the same.

  • AZ Thumpdaddy

Posted October 13, 2008 - 06:50 PM

#3

I have an 07. I visited Racetech 2 months ago and gave them my specs = 225lbs and desert riding. They recommended leaving the front springs alone (.47) and to change out the 5.5 rear to a 5.8. No problem in setting sag properly with the 5.8. Cost is $110. Call them. Use the clickers to dial per the manual.





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