progression of pds

[prcucuma]

Hi!
I just wanted to start a new thread about the never ending story pds...
So, last week I was talking to someone from race tech. He showed me some graphs proving that the pds has less progression than a honda cr with linkage. Therefore they have some new springs which a more progressive than the stock ones. Sounds good this far. Only problem until now is that you get two WP springs for the price of on RT spring (at least here in europe). Then I heard that the gp racers would use straight rate springs on the shock, when I looked at them I saw progressive springs...
A friend of mine is quite fast and the hardest progressive spring (PDS4) was way to soft, I gave him a straight rate spring 97-250 and he was completely happy with this one. The sag was correct and even on small bumps it was supple. But I must admit that the shock is revalved and has a bladder. AND the 2004 KTMs have a stock straight rate spring.
Now it is up to you to talk about progressiveness and spring rates.

Cucuma

 

[marcusgunby]

Thing is you can mimac a Cr rising rate spring with a race tech version-but you are not matching the damping curve to suit-just the opposite, and now you have to control that really strong rebound(when shock is bottomed) of a PDS99 or whatever race tech call it.If you could test a pds shock on a dyno i bet it would be low in damping and then hit a wall as the 2nd piston come in.

 

[prcucuma]

Thats the reason why they are changing the needle to different lengths and diameter. Has anybody tried to work with the needle for a different progressive action?

 

[marcusgunby]

Yes lots of tuners have-whos got it right-hmmm?

 

[prcucuma]

Looks like you don't think you got it right....right? It would be really interesting to have a dyno where you can put the frame/shock/swingarm into and then try and try and try to copy the curve of a linkage. At least it would be nice to see where we are with the pds.

 

[prcucuma]

Hi marcus,
do you know how the WP shims work that have for example a 28 OD, a 26.25 ID with a thickness of 0.3mm and a second shim inside with a 26 OD, 14(?) ID and a thickness of 0.25mm. In theory this combination brings the smaller shims into play and after a deflection of 0.05(or whatever) the 26/14/0.25 finally makes everything a little bit stiffer...
Might this be somehow in the right direction? If this is right, then you might use this for a plush setup with some bottoming resistance, right?

 

[marcusgunby]

I never played with different needles-my 99 had a shorter one fitted by a local tuner-it wasnt a bit improvement -i have my doubts as they have gone in a complete circle in 6 years.

On the shims its a preloaded setup-its similar to a dished piston-ive rode with that setup (on the rebound stack) and ive rode without-not a great difference, the trouble is with the pds is it has so many variables.