Nol, 95 993 C4

When researching shock replacement options and supsension upgrades on Gert's site I noticed that very different combinations of spring rates are used by the H&R and PSS-9 setups:

H&R : Front: 290-310
Rear: 350-370.

PSS9: Front: 225 - 250 lbs
Rear: 400 - 685 lbs

Notice how the popular PSS9 has a much bigger difference in spring rate front to rear. Softer in the front and much stiffer in the rear compared to H&R. I know the damping rates are important too but this stiffening of the rear end must make a big difference to the handling of the PSS-9 equiped cars.

Anyone noticed this from "seat of the pants" feeling of their car before & after? Would it help to reduce understeer for my C4?

The standard US suspension is 150-200 front and 225-275 rear according Gert's site, but I can't find the ROW M030 values. Can someone chime in with these?

For now I'm leaning towards replacement with Bilstein HD shocks or Gert's Bilstein HD "package" with ROW M030 depending on the spring rates. I can't see the need (yet?) for the adjustable features of the full PSS-9/RSbar set-up on my street ride. But I am more than curious about the stiff rear end and what it could bring.

Enjoy <img src="graemlins/burnout.gif" border="0" alt="[burnout]" />

Nol,

RLM#: 020825-2307

PS: On setting up full suspension mountainbikes I take care to balance the suspension components in rate and feel for front and rear to get a decent handling rig. The actual spring rates you end up with depend a lot on suspension geometry. But once that is sorted you can't just "up" them by a couple of 100 lbs on one end only and not notice a huge difference. I do assume the same applies to cars, right?

PPS: this could be "the" difference we're all looking for of course!

Matt Vaughan

Hi Nol, take notice that the H&R setup (street version) is a single spring, and the Bilstein, a dual spring. On the PSS-9 rates noted on Gert's site, each value represents each spring. Another consideration, besides spring rates is the shock valving. Now both kits use Bilstein shocks, but the valving is different, which can change the characteristics considerably.

DJF1

Ok Matt you confused me.! Where is the 2nd spring on the PSS-9??? The springs from gerts photos looks to be similar progressive like the H&R. <img src="confused.gif" border="0">

Matt Vaughan

The 2nd spring is a tender (smaller) spring, and then you have the longer, main spring.

Nol, 95 993 C4

Hi Matt, you make very valid observations but still I think there is a key difference.

About the dual springs. Note the tender srings in the rear of the PSS-9 are stronger then the H&R single. AFAIK tender springs are for small bump compliance, and they are stronger then the H&R. Then the "progression" from 400-685 is
very strong again, whereas progression in the front is minimal at 225-250. The rear end is seriously stiff in my opinion

About damping rates, there is reral scope for working the behaviour. I think the most interesting difference (or not) would be compression damping settings between the
two systems. And what does the PSS-9 adjustment change, compression damping, rebound damping or both?

Any of the guru's out there who have probably tried many variations with comments?

Enjoy <img src="graemlins/burnout.gif" border="0" alt="[burnout]" />

Nol

RLM#: 020825-2307

DJF1

The only observation I can offer you Nol is from my own experience at the track with the H&R coilover system. I set up the car to RS specs and the ride height between the Euro M030 and the RS specs. Also in my setup i added the Euro M030 sway bars. The way the car is set it was very neutral on the track , I did not encounter any understeer tendencies and when the track became slick or I became very tired and sloppy I had a couple of small oversteer moments which were very progressive and correctable. I really love the way the car is setup. I would really think that this is the way it should have come from the factory... I must admit that I'm not experienced at all with 911's all my previous P-cars and others were front engine ones. So oversteer was something that always "scared me" the legend of the 911 famous tail hangout tendecies for years precluded me from looking at a 911. Now my opinion has changed along with my level of experience from the track days and I'm more ready for it however I still like a neutral setup with plenty warning before I get out of shape and the H&R does exactly that.

Matt Vaughan

[quote]Originally posted by Nol, 95 993 C4:
<strong>Hi Matt, you make very valid observations but still I think there is a key difference.

About the dual springs. Note the tender srings in the rear of the PSS-9 are stronger then the H&R single. AFAIK tender springs are for small bump compliance, and they are stronger then the H&R. Then the "progression" from 400-685 is
very strong again, whereas progression in the front is minimal at 225-250. The rear end is seriously stiff in my opinion

About damping rates, there is reral scope for working the behaviour. I think the most interesting difference (or not) would be compression damping settings between the
two systems. And what does the PSS-9 adjustment change, compression damping, rebound damping or both?

Any of the guru's out there who have probably tried many variations with comments?

Enjoy <img src="graemlins/burnout.gif" border="0" alt="[burnout]" />

Nol

RLM#: 020825-2307</strong><hr></blockquote>

I agree that there is a bigger difference in the rates F to R on the Bilstein kit. The only thing I can think of is that Bilstein wanted to aide in keeping the rear from squating under hard acceleration, which is apparent in our rear engined cars.

My point about the shock valving is that it makes a big difference. Just as a point of reference, I had an RSR setup on my '95 car with 300# front and 500# rear spring rates. This setup was a much firmer ride, albeit there were differences such as a single spring and monoballs.

The PSS-9 kit is adjustable compression and rebound. When making these adjustments you really see the difference the shock can make. It's a great kit all the way around.