Help with harsh ride (going from track to daily driver)

Porsche Technical related discussions.

Help with harsh ride (going from track to daily driver)

Postby lagrasta on Sun Nov 03, 2013 5:26 pm

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
Mike LaGrasta
99 911 (with some stuff added and some stuff removed)
lagrasta
Member
 
Posts: 41
Joined: Mon Sep 28, 2009 9:20 pm
Location: Mira Mesa

Re: Help with harsh ride (going from track to daily driver)

Postby Greg Phillips on Sun Nov 03, 2013 10:13 pm

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

Greg
Greg Phillips
SDR Past-President @ 2014 Instructor of the Year
1982 911SC coupe, 2002 Boxster S (the track cars)
1989 928S4 & 1992 968 M030 (the black cars)
2019 Hertz Z06 Corvette & 2005 Boxster (Pat's car)
User avatar
Greg Phillips
Pro Racer
 
Posts: 1549
Joined: Wed Jun 30, 2004 11:41 am
Location: Coronado

Re: Help with harsh ride (going from track to daily driver)

Postby lagrasta on Mon Nov 04, 2013 12:14 am

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!
Mike LaGrasta
99 911 (with some stuff added and some stuff removed)
lagrasta
Member
 
Posts: 41
Joined: Mon Sep 28, 2009 9:20 pm
Location: Mira Mesa

Re: Help with harsh ride (going from track to daily driver)

Postby rshon on Mon Nov 04, 2013 2:13 am

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).
Russell
PCA Zone 8 Rules Tech Advisor
Z8 TT/DE Chair ('20-'22)
Z8 Rules Chair ('12-'18)


Porsche Boxster S
Scion FR-S
Lotus Exige S
Toyota 4Runner TRD Off Road
User avatar
rshon
Time Trialer
 
Posts: 356
Joined: Tue Feb 14, 2006 8:07 pm
Location: Tace et Fruor Equito

Re: Help with harsh ride (going from track to daily driver)

Postby Cajundaddy on Mon Nov 04, 2013 7:56 am

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.
Dave Hockett
09 Cayman 2.9L PDK #129 (with a few tweaks)
CC08
PCA GPX CDI- Past
PCA National DE Instructor
User avatar
Cajundaddy
Time Trialer
 
Posts: 466
Joined: Sat May 17, 2008 1:29 pm
Location: Kuna ID

Re: Help with harsh ride (going from track to daily driver)

Postby lagrasta on Mon Nov 04, 2013 4:08 pm

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.
Mike LaGrasta
99 911 (with some stuff added and some stuff removed)
lagrasta
Member
 
Posts: 41
Joined: Mon Sep 28, 2009 9:20 pm
Location: Mira Mesa

Re: Help with harsh ride (going from track to daily driver)

Postby Jad on Mon Nov 04, 2013 4:46 pm

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.
Jad Duncan
997 S Cab - Sold
996 "not a cup car" Sold
Tesla Model S
Porsche Taycan
https://www.goldfishconsulting.com/
User avatar
Jad
Pro Racer
 
Posts: 1788
Joined: Wed Jun 30, 2004 11:03 am
Location: Del Mar

Re: Help with harsh ride (going from track to daily driver)

Postby kleggo on Mon Nov 04, 2013 7:38 pm

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
User avatar
kleggo
Time Trialer
 
Posts: 399
Joined: Wed Jul 25, 2007 4:43 pm

Re: Help with harsh ride (going from track to daily driver)

Postby Cajundaddy on Mon Nov 04, 2013 8:38 pm

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.
Dave Hockett
09 Cayman 2.9L PDK #129 (with a few tweaks)
CC08
PCA GPX CDI- Past
PCA National DE Instructor
User avatar
Cajundaddy
Time Trialer
 
Posts: 466
Joined: Sat May 17, 2008 1:29 pm
Location: Kuna ID


Return to Technical

Who is online

Users browsing this forum: No registered users and 52 guests

cron