Join Date: Apr 2005
Location: SW Washington State
The preload spacers are used to set the suspension up to the riders weight, but because you can't tell what the amount of preload is prior to install it is a bit of a catch-22. Common wisdom is to set the preload to where the sag is 1/3rd of the total suspension travel when the bike is loaded with normal gear and the rider.
So with the new Progressive springs if you knew what the designed weight of the rider was or others experiences in using the same springs and their riding weight it would get you in the ballpark of the correct length. Another issue with this tuning is that the length of the spacer is not a direct coorelation between the current sag amount and the amount one is tuning for. That is, if the sag is 1" too much, adding 1" to the spacers will not give you just 1" less sag. Most often you will get much less than 1" of sag due to the progressive wound nature of the springs.
Long post later, you will probably find the Progressive spacers a better choice when shooting blind into the forks for setup. At least these two pieces were designed with the bikes weight, spring coil rate and an "average" weight rider in mind. The time I've contacted Progressive about the average rider weight I was told 170-190 lb's. if your coming in heavier than that I would add maybe .25" in length for each 20 lb's above and shorten them the same by about the same for each 20 lb's below average.
I'm having a bit of trouble sorting out the suspension on my new to me '03 1000, it has been fitted with Wilbers springs and an Ohlin's SU201 rear shock. Beautiful piece of engineering but I'm quite sure the earlier owner had no idea what he was doing with the setup unless he ran around 400 lb's and carried sheet rock on the tail rack.