Ron

01-24-2010, 10:33 PM

I've known for some time that spec's for Polaris drive clutch springs list finish rates with slightly different measurements. Polaris and Team calculate spring rates from a starting point of 2.5" to a finish rate at 1.19". Others such as SLP and EPI use 2.5" and 1.25". The .06" difference doesn't seem significant until you do the math. I was graphing some springs to visualize the intermediate loads and revised an SLP rate to an additional .06" of finish.

On the very popular SLP Blue/Pink Spring the finish rate changes from 340 to 350. And that calculation assumes that the spring rate is constant from start to finish-the rate likely increases as the spring gets shorter....this would make the adjusted finish number even higher.

Here's my math and the results (Please disagree if you see an error in my calculation)

SLP Blue/Pink is 140/340 so it changes 200#'s (340 - 140) in a distance of 1.25" (2.5" - 1.25") 200 divided by 1.25 is a change of 1.6#'s per .01" of travel. So .06" of additional travel would leave a finish rate 9.6#'s more-adjusted to the Polaris measurement. (6 X 1.6 = 9.6)

So the spring that you thought was a 140-340 may actually be a 140-350. I bring this up because it may contribute to issues at high altitude where you run lighter weights and have trouble getting full shift. It's a big step from the stock 800 spring at 140-330.

An easier way to recalculate the rates on springs with a 1.25" finish is to add 4.8% (6/125) to the change from starting rate to finish rate (340-140*4.8%= 9.6).

On the very popular SLP Blue/Pink Spring the finish rate changes from 340 to 350. And that calculation assumes that the spring rate is constant from start to finish-the rate likely increases as the spring gets shorter....this would make the adjusted finish number even higher.

Here's my math and the results (Please disagree if you see an error in my calculation)

SLP Blue/Pink is 140/340 so it changes 200#'s (340 - 140) in a distance of 1.25" (2.5" - 1.25") 200 divided by 1.25 is a change of 1.6#'s per .01" of travel. So .06" of additional travel would leave a finish rate 9.6#'s more-adjusted to the Polaris measurement. (6 X 1.6 = 9.6)

So the spring that you thought was a 140-340 may actually be a 140-350. I bring this up because it may contribute to issues at high altitude where you run lighter weights and have trouble getting full shift. It's a big step from the stock 800 spring at 140-330.

An easier way to recalculate the rates on springs with a 1.25" finish is to add 4.8% (6/125) to the change from starting rate to finish rate (340-140*4.8%= 9.6).