PCA SDR

I've had to convert the dedicated ax car (99 Boxster) back to daily driver street use and the harsh ride is killing me. I could use some input on how to approach this. I've found some really...um...diverse...info on other forums. BTW, "harsh ride" is subjective but I'm talking about sudden unforgiving jolts that rattle the whole car and shake parts of me I don't want shaking on the way to work.

Here's what may be contributing to the issue:
* pss9 coil overs
* lowered ride height
* Tarret adjustable sway bars and drop links
* possibly bad bushings?

I've been told that the PSS9s can be set to "softer than stock". I'd have to compare to a stock car to be sure, but I'm not getting that even at it's softest settings of the 1-9 damping adjustment. I'm no expert, but I was also thinking that the ride height shouldn't be causing this because these units allow that to be set independent of the spring settings. Is this correct? Are there even settings on the springs that I can adjust such as pre-load?

I'm also suspecting that the sway bars in their harder track positions would transmit more vibration through the chassis. Is this true?

As far as bushings are concerned, the car is old enough to need it but I'm not hearing the tell tale noises that most people are describing. I suppose it's probably worth doing anyway at this age.

Anyway, I'm just looking to get some basic info and educate myself before making any drastic decisions. Any input or advice would be greatly appreciated.

Thanks,
Mike

Another factor may be tires, lower profile will also be stiffer.
Switching back to 16" is another way to soften the ride.

Greg

Yes, that is an excellent point that I left off the list. I am running some pretty low profile 18's right now. I'm sure that is a factor, but I can't imagine it's the whole issue. Easy enough to try out that one since I still have my OEM 17's.

Thanks a lot!

The springs that come with Boxster 986 PSS9's are definitely much firmer than stock. Setting the shocks to full soft will allow more compression travel and rebound, but will not lower the inherent spring rate. To "soften the ride" you'll need to switch to springs with a softer/lower rate, or go back to a setup with stock-style shocks and softer stock-style springs.

Also, the stiffer sway bars do also contribute to the ride harshness under certain conditions (hitting bumps with your outside tires while cornering, as they promote more weight transfer to the outside wheels).

If you are running stock PSS9 springs they are progressive so setting the shock full soft and sways full soft should add a lot of comfort. If you went with BSR 450/500 springs you will need to change them to soften the ride. My car with stock PSS9 springs is dual purpose and it is a little firm for street and a little soft for track but a good compromise for me.

Wow. I just got off the phone with Bilstein and then Swift Springs. I didn't get a whole lot of confidence in their knowledge of their own product, but here is what they told me.

The Boxster PSS9 springs are:
Made by Hypercoils
Linear
255 front
340 rear
60mm I.D.
Can be replaced with shocks that are 50 pounds per inch harder or softer

I couldn't get a hold of Hypercoils, but I did talk to Swift Springs, who I believe get a lot of use in the spec boxsters. They said the I.D. is 70mm. They also said the softest they had was a 223 and suggested a rear of around 280 to go with that.

Anyone have a real measurement on the I.D. on these springs?
How do I figure out what rate to go with?

Anyway, I'm still going to try and get in touch with Hypercoils. If I can verify any of these numbers, I may do a spring swap. At under $400, it seems like it would be worth trying before some more drastic move.

I agree with Greg, put the 17" rims on and buy nice All Season comfort tires instead of Summer Only sport tires and you should get the most comfort per buck and it would be easy to switch back to performance rims and tires when wanted.

do you have adjustable ARBs?
if so, set them to full soft
set P9s to full soft, (make sure you turn the knob the correct direction).
enjoy the plushness

Mike,

If you have stock PSS9 springs just set shock and sways to full soft or put stock sways back on, and mount your 17" tires for a smooth ride. Springs are a lot of work ($$$) and will screw with your alignment and corner balance ($$$). Choose this as a last resort as it is just as much work to replace the struts with stock ones.