I finally bit the bullet and bought springs for my XPT 4. HUGE improvement!!!
The stock rates are pretty good but with the upper spring being so short, it crosses over to the heavy lower spring really early in the stroke (both the front and the back). So at ride height, it is riding pretty much entirely on the lower spring.
The stock rates are 290 over 298 in the front and 241 over 289 in the rear. The formula for calculating combined rate is:
Spring1 x Spring2 / Spring1 + Spring2
So using the front for example......
290 x 298 / 290 + 298
86,420 / 588 = 147 lbs/in
So the front combined rate is 147 lbs/in and the rear is 131 lbs/in. With the upper spring completely collapsed at ride height, it takes the combined rate out of the equation and you are sitting on the 298 lbs spring in the front and the 289 lb spring in the rear. That is about two times the necessary rate which, as you can imagine, hurts the ride tremendously.
The Eibach Stage 2 kit uses a 300 over 300 in the front for a combined rate of 150 and a 250 over 300 in the rear for a combined rate of 136 so the combined rates are similar to stock but give you WAY more combined rate travel (the way Polaris should have done it!). It includes 8 crossovers and you can control when it transfers to the heavy lower spring by threading the crossovers up or down the shock body. One of the cool thing about the Fox Shocks on the Turbo is the lower portion of the body is a smaller OD which allows the use of traditional crossover without disassembling the shock. Simply slide the crossover up the onto the bottom of the body and thread them on. No more allen wrenches to make adjustments! Most of the year I leave them threaded pretty far up the body and have it crossover really late in the stroke and then for the dunes I will thread them back down and have them come in 65-75% of the way through the stroke.
There is also a Stage 3 kit if you have added A LOT of weight but I feel the Stage 2 kit will be the answer for the majority of people.
The stock rates are pretty good but with the upper spring being so short, it crosses over to the heavy lower spring really early in the stroke (both the front and the back). So at ride height, it is riding pretty much entirely on the lower spring.
The stock rates are 290 over 298 in the front and 241 over 289 in the rear. The formula for calculating combined rate is:
Spring1 x Spring2 / Spring1 + Spring2
So using the front for example......
290 x 298 / 290 + 298
86,420 / 588 = 147 lbs/in
So the front combined rate is 147 lbs/in and the rear is 131 lbs/in. With the upper spring completely collapsed at ride height, it takes the combined rate out of the equation and you are sitting on the 298 lbs spring in the front and the 289 lb spring in the rear. That is about two times the necessary rate which, as you can imagine, hurts the ride tremendously.
The Eibach Stage 2 kit uses a 300 over 300 in the front for a combined rate of 150 and a 250 over 300 in the rear for a combined rate of 136 so the combined rates are similar to stock but give you WAY more combined rate travel (the way Polaris should have done it!). It includes 8 crossovers and you can control when it transfers to the heavy lower spring by threading the crossovers up or down the shock body. One of the cool thing about the Fox Shocks on the Turbo is the lower portion of the body is a smaller OD which allows the use of traditional crossover without disassembling the shock. Simply slide the crossover up the onto the bottom of the body and thread them on. No more allen wrenches to make adjustments! Most of the year I leave them threaded pretty far up the body and have it crossover really late in the stroke and then for the dunes I will thread them back down and have them come in 65-75% of the way through the stroke.
There is also a Stage 3 kit if you have added A LOT of weight but I feel the Stage 2 kit will be the answer for the majority of people.