Progressive Rate Springs

[TimSr]

I got mine from dennis kirk today. Installed them, and replaced the 30wt fork oil with some 20 wt, used the enclosed preload spacers which were actually PVC pipe, and took it for a test run. WOW! What an improvement!best $80 I ever spent. Cant wait to test them on a track to see how they do on jumps.

[Dynofox]

Glad to hear it, when I have my forks rebuilt again I might through those in mine too.

[hrc200x]

good to hear, I considered it but $80 seems spendy. What all did it improve? just make them stiffer?

[plkmonster2]

progressive springs get alot tensor as they get compressed, helping handling, and they keep the shock from bottoming out too easily.

[TimSr]

Here is some suspension 101: Stiffer is not better. Lighter is better. The lighter your suspension the better your ride. Problem is, when you get too light, you have two problems. You bottom out too frequently, and you nose dive during heavy braking, cornering, and downhills. Normally you have to resort to going stiffer to correct these problems, but at the expense of your once plush ride disappearing. My Z had a great ride, but when I started racing motocross, I had to preload the heck out of them, add a little air, and run 30 wt fork oil. Its handled and jumped a lot better, but it cruised light duty bumps like an ATC70! Then when I slid the forks up in the tubes, all the weight shifted forward, putting more weight on the springs than they were equipped to handle. I added a little air to compensate, but its rode rough, dived a lot, and the while 30 wt oil for dampening slowed bottoming out, suspension response to bumps was way too slow.

Progressive rate springs, means the spring rate changes progressively as they are compressed. The windings change from close together at one side to farther apart at the other end. The idea is your springs are really light for the first couple of inches which gives you that nice smooth ride, but the farther they are compressed, the stiffer they get, which means front end dive is limited to the extend of the "light range". When you jump, buy the time your spring compresses to the bottom, its got heavier spring action than conventional rough riding heavy springs do, and is therefore less prone to bottom out. Its the best of both worlds, and adjustment to the riders weight is not nearly as critical, and can easily be done by changing the length of the preload spacers. I poped them in as they were, and its seems to be perfect. NO sag when I sit on it, but the lightest bumps have my forks compressing and soaking them up, and no brake diving. As I mentioned, the only thing left to test is jumping, and some whoops, but from what I can see so far, it looks promising.

[samster143]

Thanks Professor

[Blazin350X]

Tim,
I've been contimplating on installing a set of progressive springs in my 350X, to help the pounding in the trails. Do these springs physically have different diameters along it's length or are they the same diameter with different wire sizes??
The only reason I ask is I just rebuilt my forks on my 350X and according to the manual the stock spring is supposed have a taper at the lower end and I could not see the difference on mine and was wondering if maybe they weren't stock springs??
I run my 22.5 front tire at around 1.5 pounds of air to help smooth out the trails, but I'm not to crazy about running an almost flat front tire. It's not to bad in the trails, but when I get in the pits I don't like to jump with the tire that soft. I did install ATF this time in the forks and it seems to have helped some in the ride, but I haven't been in the pits yet to see how it will hold to a jump.