996 Cab unstable at speed ?

[bud22405]

01 Tiptronic C2 Cab- 62K
Kuhmo Ecsta SPT XL tires 6k miles

Newbee here to both Porsche and this site. When either accelerating rapidly to say 90 or so and even when staying around that speed for some time, my 01 996 Cab seems very light in the front end. The steering gets very loose and somewhat scary. :o The car just doesn't feel "planted" or stable My other car is a big heavy LS430 and it is very solid to 100+. The cab is entirely stock US. Is this to be expected in a 911, does it require a "dealer" visit, or what is the best inexpensive fix (besides slowing down) that might correct this "problem, if it is indeed a problem? The car is otherwise fine.

[RFM]

Porsche cars should have a tight grip at that speed whatever the type of suspension is, there are several points to check/improve: steering system + pump - excessive play/slack - pump pressure too high (uncommon) /// Shock absorbers test - faulty/leaking /// Suspension in general - cracked or used silent blocs/excessive play ball joints /// Alignment /// Use approved tyres brand/dimensions. Hope it helps.

[Foster]

I've experinced that feeling and it was just the tire pressure.

[GranburyChuck]

I think you may be feeling the rear engine bias of the Porsche versus your Lexus. When I first started driving a Porsche I felt that the front was not well planted. At high speeds the sensation felt more pronounced. Remember only about 40% of the weight is on the front end in a Porsche. In you Lexus its probably closer to 60% and a much heavier car. Tire pressures will play a role but I think you just need to get used to this new weight bias.

[john in lb]

01 Tiptronic C2 Cab- 62K

Kuhmo Ecsta SPT XL tires 6k miles

Newbee here to both Porsche and this site. When either accelerating rapidly to say 90 or so and even when staying around that speed for some time, my 01 996 Cab seems very light in the front end. The steering gets very loose and somewhat scary. :o The car just doesn't feel "planted" or stable My other car is a big heavy LS430 and it is very solid to 100+. The cab is entirely stock US. Is this to be expected in a 911, does it require a "dealer" visit, or what is the best inexpensive fix (besides slowing down) that might correct this "problem, if it is indeed a problem? The car is otherwise fine.

There is definitely something wrong with your car. The car gets into the "groove" starting at 80 and keeps getting better as you go past 100... It should definitely feel better than the Lexus (not even a close comparison).

Good luck.

[der meister]

I think you may be feeling the rear engine bias of the Porsche versus your Lexus. When I first started driving a Porsche I felt that the front was not well planted. At high speeds the sensation felt more pronounced. Remember only about 40% of the weight is on the front end in a Porsche. In you Lexus its probably closer to 60% and a much heavier car. Tire pressures will play a role but I think you just need to get used to this new weight bias.

I tend to agree with this, probably just take a while for you to get used to the different feel of a rear-engine 911 at speed.

Did you have a PPI when you bought the car? Are the tires in good shape? Had an alignment lately? Maybe check the toe-in?

I've also had a similar feeling, but then I realized it's a different feel and just highly responsive with a whole lot of grip.

Good luck and enjoy!

[nick49]

The tires require a lot of pressure and handling, especially high speed will deteriorate if they are under inflated. Go by the manual and you should notice a big difference. The ride is usually harsher with more pressure and most tires I've used will loose air and need to be filled fairly often.

[bud22405]

The tires require a lot of pressure and handling, especially high speed will deteriorate if they are under inflated. Go by the manual and you should notice a big difference. The ride is usually harsher with more pressure and most tires I've used will loose air and need to be filled fairly often.

I'm sure the tire pressures are ok, the tire brand i'm not sure of. i thought maybe an air dam or lowering the car was the common solution but i'm beginning to think it's just the difference i feel between a heavy car and the porsche. i will check the front end next time it's on the rack. thanks!

[savowood]

It could be a lot of reasons, but the most likely thing I think is either the super simple check of the air pressure, or the only slightly less simple check of the alignment. I'm guessing you might have a touch of toe-out in the front, or even the rear. Unless you're tracking the car, I'd stay away from toe outside of the stock settings. Stock for the front IIRC is dead straight. The rear might have a little toe-in, but not much.

P-cars are very reactive to minor suspension changes. Once you get it dialed-in, you'll be very happy with the feel.

-Michael

[RF5BPilot]

...most likely thing I think is either the super simple check of the air pressure, or the only slightly less simple check of the alignment. -Michael

+1

Recheck pressures. Previous owner may have, by accident or design, created a non-stock alignment. Esp. a setup for the track + older/harder tires + uneven roads can create instability. Old damage could have thrown things off. Bite the bullet & have a good alignment shop, recommended by other Porsche owners in your area, check it out. It's also worth it to make sure you're just not feeling wider, older tires responding to worn cart-tracks on local roads.

Edited January 13, 2009 by RF5BPilot

[yasuro]

here's a very basic question:

did your car come with a fixed rear wing?

i've seen a rash of cars with incomplete aerokits. if you have a fixed rear spoiler without a corresponding front lip you'll experience float and the car is unsafe to drive at speed.

Edited January 13, 2009 by yasuro

[bud22405]

here's a very basic question:

did your car come with a fixed rear wing?

i've seen a rash of cars with incomplete aerokits. if you have a fixed rear spoiler without a corresponding front lip you'll experience float and the car is unsafe to drive at speed.

nope, no wing. i'll take it in for an alignment

[KevinMac]

I do notice a difference when the gas tank is full.

[maniac]

01 Tiptronic C2 Cab- 62K

Kuhmo Ecsta SPT XL tires 6k miles

Newbee here to both Porsche and this site. When either accelerating rapidly to say 90 or so and even when staying around that speed for some time, my 01 996 Cab seems very light in the front end. The steering gets very loose and somewhat scary. :o The car just doesn't feel "planted" or stable My other car is a big heavy LS430 and it is very solid to 100+. The cab is entirely stock US. Is this to be expected in a 911, does it require a "dealer" visit, or what is the best inexpensive fix (besides slowing down) that might correct this "problem, if it is indeed a problem? The car is otherwise fine.

Look for a ROW M030 sport Suspension, this one was design to work to the right handling level, like the 996 sold in europe. This will improve your handling. Suspension of US 996 is softer and the ride is higher = less handling, but more comfortable ride.

I switched to H&R springs and HD Biltein shocks, a nice front lip spoiler to reduce understeer and problem solved, now I' waiting for M030 swaybars to improve to a higher level of handling of my '02 996 C2.

Best of luck, and enjoy! :drive: