dmcentee

When I drive my car on the highway the steering seems to wander. Sometimes it drifts a little to the left, sometimes it drifts to the right. Most of my driving is on country roads and this is not a problem, but I would think that on the straightaway that when you hold the wheel steady the car should track steady. The car has 32K miles, new tires and alignment within the last year.

Any ideas?

ed devinney

Have you checked tire pressures?

TroyN

I had this issue before too. People suggest tires, to make sure you have N-rated (Porsche-approved), suspension (worn shocks) and alignment. In my case a good alignment took care of the issue. It was actually the rear settings that most affected handling, make sure your shop can properly set kinematic toe; critical for good-handling w/ our cars.

rkass

My issue believe it or not (which is exactly as you describe) was solved by checking the power steering fluid - mine was a little low and when filled to normal no more issues. Check yours. RK

orcfromthesouth

My 993 tends to wander a bit over rain grooves. It is, however, amazingly stable even at very high speeds (120 mph plus)
With heavy acceleration I feel that the front end goes a bit on the light side and is also prone to wandering. I just hold the steering tight and apply a bit of good ol'e muscle. You can't drive 993's like a luxobarge with one finger on the steering wheel!

Orc

dmcentee

Tires are N2 rated, tire pressure is good, power steering fluid level is in the middle of the gap in the stick with the engine at idle.

TroyN

What are your alignment specs, and who did it?

the_buch

Is this something new or have you had these symptoms for a while? ... Despite good alignment (apparent on a really flat, smooth surface that the car wil track straight under accel or deccel) I find my car will tramline in road ruts at any speed, and I can hardly wait to trade in my S-03s for some Michelins

dmcentee

The alignment was done at Reid Vann in St. Louis. The settings are:

-0.4 deg. left front camber -0.6 deg. right front camber
5.4 deg. left front caster 5.6 deg. right front camber
0.4mm left front toe 0.5mm left front toe

front cross camber 0.2 deg.
front cross caster -0.2 deg.
total toe 1.0mm

-1.2deg left rear camber -1.6 deg right rear camber
1.9mm left rear toe 2.0mm right rear toe

rear total toe 3.9mm
thrust angle 0.0 deg

TroyN

It seems close to reasonable except that there really should not be a difference in camber from side to side. They do sometimes do a caster difference in order to compensate for crowned roads. The stock camber settings are about 1 degree different between front and back (back having more negative, helps promote safe understeer), so your right side looks closer to correct, if stock is what you intended. As I mentioned before, it's surprising how the rear being out of spec can make it feel like the front is misbehaving.

Kinematic is important but I don't think it has very much effect when you're going in a straight line.

I'm not sure who Reid Vann is, I more meant whether it was a dealer, independent, Porsche-specialist, etc. I would trust very few to do the alignment correctly, from bad experiences with "specialists" and the dealer.

Jack of Hearts

Interesting thread. My car also suffers from this problem--with brand new Bilsteins, M030 springs set at RS height, a fresh alignment from Steve Alarcon, and new Michelin Pilot Sport (Rib) tires.

Before all that work the car would follow road grooves, but not wander.

Now it doesn't follow road grooves, but does wander.

After the new suspension and alignment, but with the old tires (Dunlop 8000s), it didn't seem to wander. In fact, I thought it handled pretty damn good--with near-slicks on the back.

My theory is that the new tires are part of the problem--if not the whole thing.

Tread squirm.

But I'm going to crawl under the car and check the tie rod ends.

If they are good I'm going to talk to Steve about more toe-in and/or more caster.

I'm interested in what others say about this. I was almost ready to post a thread like this myself.

chris

Peter B

I've been following various threads on this problem because until Friday morning my C4 suffered badly from unpredictable changes of direction. Eventually a thread on Rennlist produced a description with exactly the same symptoms..... steering wheel off-centre after pulling hard turns etc. etc.

Two new rubber shock absorbers on the track rod ends later and problem solved. The rubber boots on the rack ends were a real PIA to refit but that aside it was a simple job.

Steering geometry re-aligned (very little to alter except one TRE) and the car now behaves properly.

Not going to change it back to a 996 after all!

993inNC

IMO, you have either to much rear, or not enough front camber. These cars seem to do best when the camber values are within .5 degrees of each other. Your car may be steering from the rear end, causing the drift.

deltawedge

I would second the tie rods (track rods). I would also suspect the lower front ball joints.

chris walrod

or control arm bushings - another sign of bad control arm bushings is intermittent steering wheel wobble.