GRUWEZ

After having replaced all four shocks with Billsteins and after having installed new PU lower control arm bushings (all parts sourced from Carnewal), I am still not convinced my 1997 993 TT drives like it should. It is hard to describe the exact nature of the problem, but it feels like the handling and steering is more sloppy than acceptable. The front wheels have a tendency to "search" their own track. I understand the 4WD Porsches are liable to do this, but the effect seems to be far more proncounced on my Turbo than on my 964 Carrera 4 four instance. Also it feels like the steering is not as spot-on as on my other Porsches. It may be just my imagination, as I have not driven a single other 993 TT. Basically I have no basis for comparison. I had the suspension aligned but that did not really bring a lot of improvement. At higher speeds -- say above 180 kph -- sometimes the effect of tracking front wheels and sloppy steering is really pronounced when the road surface has "truck tracks" (pretty common in traffic-heavy Belgium).

Any ideas what could be wrong?

Thanks for the input!
Rik Gruwez

No HTwo O

Rik, how old are your tires? Tire pressures? Are they a matched set?

GRUWEZ

Hi No HTwo O,
Since I cannot seem to find a date code on the tires, I can only rely on the fact that they were on the car when I bought it 5.5 years ago. So they must be at least that old, perhaps older. They are a matched set of Bridgestone S02. I set the tire pressure to 2 bar (29 psi) on all four tires.

Regards,
Rik

Felix

Those pressures are quite low in comparison to what Porsche recommends (36 and 44 psi); try the higher pressures and see how you get on.

Who did the alignment and do they have the equipment to properly adjust the kinematic toe on the rear?

911/Q45

I wouldn't back out of the driveway on tires that old!

burton

Sounds like it could be an alignment issue, particularly the tramlining you describe. If you are confident in the alignment (kinematic toe is key as phelix suggested), sloppy steering could be spent tie rods. There is a post on the 993 board you may want to look at: "Very Odd Steering Behavior ('95C4)."

Felix

You should be able to find a date code as a 4 digit number located inside an oval.

GRUWEZ

I probably should kick myself in the head for not checking the correct tire pressure settings. I set them to 36 psi front and 44 psi -- as suggested by the overly obvious door jamb sticker -- and that improved matters dramatically. Thanks for pointing me in the right direction! Sometimes the obvious things are too easily ignored.

The alignment shop did not have the tools to do the kinematic toe on the rear. They used their alignment computer and the eccentrics in the rear to set the toe, based on what the alignment computer read with its lasers and the optic mirrors mounted on the rear wheels. Is the kinematic adjustment so much different. I read about it in the shop manual but have not gotten to the bottom of it.

Yeah I know, I definitely need to get new tires in the front. ;-)

Tie rods were OK at the last technical inspection last September. Since then I put maybe 500 kms extra on the car. Still it is good to know this could be a cause for sloppy steering. Thanks for the link to the posts on the 993 board.

Regards,
Rik Gruwez

Felix

The inner ends of the track rods can soften with age permitting front toe changes under load. Have a look at https://rennlist.com/forums/993-foru...rod-inner.html

If the kinematic toe is off you can get a static alignment that is in spec but as the rear suspension compresses and extends you may get toe changes that affect the stability of the car. Definitely worth getting it checked by someone who has the right equipment.

Turbodan

all tires sold in the last 12 years in north america have a date code. probably same in europe. it has triangles on either end of number and may be on the inside. this could be your problem. and there is no way I would be going 180 KPH with tires over 12.
for comparison, my car is very stable at those speeds.

Barney1

Bridgestone S02 is not my first choice for a tire, plus they are old. I have Conti. contact 3's and love them.
Yes 44psi rear and 36psi front is the best tire pressure.

No HTwo O

Rik, here is how you read a tire code date. Glad you and your car are doing better:

http://www.tirerack.com/tires/tirete...jsp?techid=11&

NoSubEDU

A few things to check:

1) Alignment
2) Tie rods
3) Are you lowered? If so, RAISE the car.
4) Strut Brace

My TT rode like crap for a year. I finally raised the car for the 2nd time and it's an entirely new car. My car was WAY too low and it affected the suspension geometry.

ScottMellor

That's a fairly sweeping statement, and not necessarily correct.
It alllll depends.......

NoSubEDU

Allow me to rephrase - Perhaps your car is TOO low.

I had been fighting handling issues for about a year on my TT - ever since I purchased the car. I had already raised it once. As it turns out, the car was still too low, would rub occasionally, but much more important the shocks didn't have sufficient travel. This caused "darty" steering. I raised the car (still much lower than stock) and the car drives completely different.

Even with the RS/GT2/Motorsport tie rods the car was still too low to make good use of the suspension.