Ken,

First thing you want to do is change out to a "turn buckle" style toe arm in the rear that will allow you to control the bump steer and make it equal on both sides at about 1/32 of gain per inch per side. Next, you need to get rid of those huge chunks of rubber in the A-arms near that ball joint where the radius link connects and replace them with solid mounts. Then do a basic alignment with about an 1/8" total toe in the rear and about 1/32" total in on the front and you'll be planted. Don't for get to corner balance 50/50 cross weight

 

Cary, where are you? I've been trying to get a hold of you...

 

I am not an expert but I would contact Mike at Powertech 973-586-3210 since they do racing and stock setups. Also, Euro tire in fairfield. They are really good and work on Porsches all the time.

Arnie

 

Ken I was having all kinds off issues till I took it to Eurotire. It came back a new car and the only thing that I have seen is the PSM information light has come on during high speed. I think this is probably related to having the 19's

 

So, here is the latest and greatest concerning the suspension:

I went to Eurotire yesterday and we decided to start our forensics with an alignment check.

A little background is necessary here. Eurotire installed my PSS-9's and aligned it at the time (July 2003). Shortly after that, I returned to have them raise the rear slightly to give the car a visual downward rake since it looked like it was squatting slightly. In my infinite wisdom, or is it ignorance, I told them not to realign it at that time.

Well, yesterday's alignment check revealed a slight TOE OUT at the rear!!!!!! They attributed it to a combination of springs settling as well as the height adjustment. Nonetheless, that is now corrected. After a drive, the high speed stability issue is gone. One problem solved! Classic textbook stuff....I love it!!!

Now, for the harder, or should I say softer (as you will see), issue.......the handling through a turn.

They said my suspension appeared to be much stiffer in the front as compared to the rear. That is surprising since my dampers were set at 3 front and 2 rear. I originally did this to try and induce some oversteer in the otherwise understeering car. (Remember, the lower the number the stiffer the damper setting)

Since all of the alignent specs were checked and tweaked, and the bump steer was reviewed and is not an issue, he recommended we set the fronts a little softer and see if it helps. His premise was that the combination of stiff 19" tire sidewalls and stiff suspension wasn't working for me.

Well, I tried a long sweeping left hander at speed after leaving the shop and it was not good. Really not good! The front end seemed to pogo and with each unweight of the front (pogo up) it would sort of drift out and each reweight of the front (pogo down) it would turn in!! Now keep in mind, this is occurring at a rate of roughly 2x a second or so. Completely unmanagable. It was far better before the change!!

So, as a final trial, they directed me to try the dampers at full stiff.....numero uno!! I will set them there and try it out. I haven't done so yet.

I tend to agree with this last direction. I am starting to think that the 19" tire sidewalls are so stiff, the dampers need to be compatibly stiff. If they are not, the suspension will oscillate too much and create a tire effect of "grab-release-grab-release" as the suspension is weighted and unweighted by the oscillating suspension.

It certainly is frustrating but I am learning alot.

I would welcome any comments in light of the above.

 

Ken: Sounds like you almost got it nailed...

Can you say 200 mph club???

On the track of course...he he

 

Adding a 19" wheel is like putting on a stiffer spring, so you
would certainly need a stiffer shock to match. Also, a 19"
wheel gives you less compliance in the tire sidewall, so the
rest of the suspension is required to move through a bigger
arc.
From your description, it sound like the shock needs to be way
stiffer. I hope it adjusts enough at full stiff.
Joe

 

Joe,
I agree. I just changed the front setting to 1. The rear is still at 2. I would have chged the rear to 1 as well but the car is on the lift and it is involved to get behind the rollbar and remove the Bose sub-box. Would you go 1 on the back as well?

Since 3 in the front was bothersome from a handling perspective and 7 was far worse, I am hoping 1 will make me happy. If it doesn't make me happy, yet improves the feel over 3, then it looks like I need a more race oriented suspension. Agree?

 

I wouldn't say you neede a more race-oriented suspension,
but rather a 19"-wheel-tuned suspension. The springs are
probably fine as-is, but it may be that the shocks need to
be stiffer to handle the extra shock from 19" wheels. Let's
hope their stiffest setting works.
Parenthetically, I would point to your issue as another tale
of the unintended consequences of swapping in 19" wheels.
Joe

 

Well, I set all four corners at setting number 1. I then took the car out for a drive. I drove it at about 6/10's as compared to 8/10's the other day but nonetheless I noticed a marked improvement over my original 3F/2R and trial 7F/2R.

Marked is not a strong enough word actually. The car is handling 100% better than before. So, I guess the valving really wanted to be stiff as hell to match well with the springs!

At this point I do not have anywhere to go outside of changing them out. I would rate the PSS-9 performance, with the current #1 all around settings, at about 80-90% of what I am looking for in a suspension.

All of this experimentation leads me to believe that I really need more of a race suspension. I have a track day scheduled for a week from now and will try this as it is. We shall see how it performs when pushed to 9/10's or so.

 

cool, congrats. Do see if you can get a Porsche racer chassis tuner to try your car for fine-tuning. Sticky track tires will also make the car feel a lot better... Joe