tsky

I have a 2004 996TT Cab with about 112K miles. Lately it feels like the steering is a little "squirrely." The steering wheel doesn't feel loose but at highway speed, the car sometimes ever so slightly changes direction and I have to compensate. At first I thought it was just the wind buffeting the car but the winds have calmed down so something is going on. It's very subtle so I don't think it's dangerous (yet).

I have new rear tires and decent tread up front. I have never replaced any suspension components (I'm original owner). It's been a long time since it's been aligned so I think I should probably start with that.

Are there any steering components that are easily checked? I'm an okay DIYer with only basic tools.

Thanks for any advice.

--Thomas

T10Chris

Ive heard of stability/steering feel issues if tires are replaced in pairs rather than replacing all 4.

Something to consider...

Macster

First the simple things:

You have to be sure all tires are properly inflated. You want a tire pressure gage that you can use to get the tire pressure to say within 1psi and 0.5psi better.

Be sure the rear tires are match the fronts in brand, model, N-rating, wear rating, tread hardness, and everything else. If unidirectional be sure they are installed in the correct direction.

What was the tire tread wear like with the front and rear tires? Even wear across the tread? Any signs of feathering/scrubbing of the rear or front tires?

If tread wear uneven or there were signs of feathering /scrubbing of the tires that's a sign an alignment is called for.

If you go this route remove all junk from the car, be sure the spare tire and tool kit is properly stowed and fill up the gas tank. Ask the steering wheel be centered. Ask for a before and after printout of the alignment settings.

Not too long ago I had new rear tires fitted -- one picked up a screw -- and the car felt a bit -- just a bit -- squirrelly for a while. The new tires need some heat cycles to shed/loose some mold release compound and then one just has to get used to the car again.

The problem is the rear tires were worn down and their diameter was reduced. (Enough that the speedo error has changed by 1mph with the near rear tires.) This reduction in tire diameter has some effect on the caster increasing it a bit. The car is a bit slower to react to steering. Understand this change happens very slowly over thousands of miles. (Nearly 20K miles in the case of my Turbo rear tires.)

With new rear tires the tire diameter is larger and all at once and this causes the caster to decrease a bit. The car can feel a bit -- just a bit -- more squirrelly -- until you adapt.

manimal

I feel a similar phenomenon on highway sweepers, and I just fitted new 245/40/18 + 315/30/18 Falkens and got an alignment. It does feel like the AWD is messing with me, to me, but I'm relatively new to the car and obviously can't prove that. It's very subtle, but it's a slight pitching -- even when I keep my steering input exactly the same. I'll probably try to get it re-aligned (again, sigh).

s65e90

What tires? Falken Azenis tend to tram line bad.

manimal

Yep, they're the RT-615K+'s. I suppose that could be all it is. I felt a slightly similar phenomenon back when I had non-matching N4 + N3 PS2's.

tsky

Thanks for the input! It did seem to start after replacing the rear tires. They have about 800 miles (mostly highway miles) at this point. The fronts aren't exactly new so maybe I should've replaced all four at once. I'll give the fronts a closer inspection for wear patterns and check pressures. The previous rear tires wore out more closer to the center of the car (which I thought was normal).

Thanks again!

Macster

My experience is I get approx. 20K miles from the rear tires and double that from the fronts. While when the 2nd set of rear tires is ready to be replaced and the front tires still have rather a lot of tread left they are essentially past their prime.

With my Boxster I tried running the front tires beyond the "40K" miles point, running them with the 3rd set of new rear tires, and for a while the car was sort of ok but then as the miles accumulated the car got, well, squirrelly would best describe it I think.

I replaced the front tires and all was well again. This experience really enforced the feeling that I am getting my money's worth out of the front tires by replacing them at the same time I replace the 2nd set of rear tires.

Also, based on my Boxster experience I have not bothered to tempt fate by running the Turbo front tires beyond the 2nd set of rear tires.

In the case of your car, 800 miles is plenty of time for the rear tires to shed their mold release compound and settle down into the tires they'll be for the next approx. 20K miles.

Oh, Porsche rear tires at least this is my experience first with my Boxster and with my Turbo seem to wear faster in the middle. At first I thought this was due to possible over inflating the tires and cut the pressures back some. It made no difference. Then I thought that maybe all my highway driving was causing the tires to "grow" in the middle due to centrifugal force and put even more air in the tires than Porsche called for for a lightly loaded vehicle. All I succeeded in doing was at some point by over inflating the front tires introduce some vague tire imbalance like vibration which was cured by just properly inflating the tires.

Kevinmacd

You could be experiency tread squirm. Put more mileage on the rears and it will probably go away.

911mhawk

This or replace everything, or somewhere in between

fpb111

Like this?

tsky

I've had the same experience: I get double the miles out of the fronts than the rears so I've replaced fronts and rears simultaneously every other time. But, I really rode the last pair of rears way too long and now I doubt the fronts will last until the next time the rears need replacing so I'll be all out of sync. Maybe I should just bite the bullet and replace the fronts.

WOTever

Do you have play in the steering when the car is stopped? Tie rods ok?

kmagnuss

My car did the same thing after just replacing the rears. I've had them on for about 500 miles now but I haven't been on the highway lately to tell if it's still doing it or not. If it is I'll be replacing the fronts also.

mcbit

At 112k miles i would expect your shocks to be shot, mine were done by about 65k miles. The care drove at speed as if it was in a cross wind even though there was no wind. It would even move around during the drying cycle of a contactless car wash. I fitted PS9/ PS10 and the car became an entirely different beast.

The only other time the car became squirrelly was when I had a GT2 rim and tyre setup, but this was more of a poor reaction to putting on the power rather than direction shifts when I was supposed to be going straight.

I've suffered lack of grip with new tires but not squirrelly or unpredictable behaviour,