crabman

Hello All,
I have a '96 997 that I purchased last year with very low mileage (approx. 7k). Since purchase, I noticed that the ABS seems to come on at a threshold below where I think it should. I know this sounds like a vague description, but I have owned and tracked other sports cars and have not felt this before on dry, smooth pavement with only moderately firm application of brakes. Current mileage is 12k

No codes are present and after searching the forums, I've found reference to cleaning ABS sensors. But, this was for a GT3, so I don't know if this would be applicable.

Tires are Pirelli P Zero with a build date of 2506, or the 25th week of '06 (old).

I'm leaning toward the thought that the tires, while they still have plenty of tread, they are shot due to age and lack of use.

I did have a recent issue with an intermittent PASM failure, that seems to have been fixed by replacing an (the?) acceleration sensor, so I do not think this is related but it is still worth mentioning.

Before spending over a grand on on a new set of shoes and seeing if this fixes the problem, I figure I might as well put it out for discussion.

Does anyone have any thoughts or suggestions about how to troubleshoot and/or fix my problem?

Thanks.

Edgy01

Wow--this is a VERY early 997! (I guess you really mean a MY06 car)...

Assuming that, I believe your problem is with the tires. They are dried out and as a result will appear to break differently than a newer tire. Never make that mistake--the age of your tires is a major issue.

I believe the basic guidelines suggest replacing tires at 6 years whether you have no tread or all your tread left. They are no longer viable.

You will find that your car will start to perform like it is supposed to. Definitely replace the tires now.

mdrums

Yep you need new tires my friend. I recommend Michelin Pilot Super Sports.

crabman

You are correct. . . Sorry for the typo and thanks for the response.

wwest

Assumption: PSM, NOT PASM! Stability control is just as likely to activate during braking as otherwise, I always look for something that has changed, been changed.

PSM might be falsely sensing a plowing/understeering condition and thereby trying to regain lateral traction at the front.

What were the earlier PSM failure symptoms?

Hella-Buggin'

+1

crabman

Definitely PASM. No symptoms, it just would happen.

https://docs.google.com/a/cernak.com...FrdHpub0E/edit (sorry for the link, but I failed uploading a pic.)

JW911

I can't believe this is being caused by 6 year old tires. Yes they start to get hard and lose some of their grip. But losing traction and causing the ABS to activate under only moderately firm braking pressure? No way. It might be prudent to replace your tires. But don't be under the illusion that this will solve your ABS problem.

Now with all this said, the 911 is notorious for having incredible braking and I have always noticed that due to the tremendous grip of the calipers on those large rotors it is relatively easy to induce ABS by pushing hard with the right foot. I would suggest you find an opportunity to drive another 997 and see if there is a marked difference in braking and ABS activation.

Edgy01

Once again--absolutely, it is the tires. When tires get hard they simply offer no traction--and ABS is all about traction. Once you replace the tires with NEW tires (don't try to buy a discount set) you will see what the 997 is capable of doing. It IS all about the tires--trust me. I've been driving these things since 1974.

wwest

wwest

1974 has NO meaning with regard to ABS operation, or even moreso, Ops car with PSM's stabilty and traction control.

Hella-Buggin'

But it is valid experience in discussing the merits of fresh rubber on a 911.
I just replaced my old tires about 6 months ago and it's a world of difference.
Mine weren't six years old but the fronts had many heat cycles on them.
I went from rolling on rocks to rolling on gum *****. The OP just bought the car so he may not realize the state his tires are in. Maybe drive another car at the dealer and see the difference for yourself.

wwest

PASM? acceleration sensor?

PASM is designed to vary the suspension "stiffness" and even height above the roadbed using various sensors....I see no acceleration sensor mentioned.

PSM's VSC mode, on the other hand, makes use of a lateral acceleration, YAW, sensor to determine if/when the car is becoming prone to under or over steering.

IMMHO it might be difficult for a driver to discern the difference between improper, unwarranted, VSC activation vs ABS activation.

wwest

On my '01 C4 on dry smooth roadbed it takes a serious level of brake pedal pressure to have ABS activate. In point of fact I think I would have to be using more pressure than would be normal...except in an actual panic braking circumstance.

I suspect that is what the Op is expressing, experience base with ABS indicates unwarranted ABS activation.

mattyf

Let me add another data point. My fronts are fairly old PS2s and I have a similar ABS issue, although perhaps not as quite as bad. Definitely the front ABS comes on when I wouldn't expect it (under what I'd consider 8 out of 10 braking). But the car still stops faster than anything in my stable.

I've got about 30% tread on the fronts and 45% on the rears. So I'm just trying to milk them a few more miles until the rears wear a little more and then I'll switch all four to PSS.

If you get your tires replaced and it solves this, make sure and let us know. I'll do the same, but it may be a few months until I get the time to do it.