wihlenfeldt

The comment on lowering the car and adjusting the alignment settings is of interest to me. what does this entail---new shocks, etc. Does it decrease the wear? What does it do to handling?

GT3BB

The outcome was that they charged me full price for two new rear tires, plus the alignment, and told me, in a polite way, that I just had to live with it. They said they were going to send the tires back to Porsche, and then they bought me a cup of coffee.

Actually I was not really mad, I expect premature wear on these things, just a bit disappointed that no concession was offered. By the way, the car was aligned twice within that span of very benign miles.

Perhaps it is like someone said above, that freeway mileage causes excess wear as opposed to the same mileage with a balance of straight and cornering mileage. The mileage on my GT3 was primarily freeway(75%) anyway.

uzj100

Maybe this has already been answered, but.....what are the factory rear camber specs and what's the actual setting on your car? Also, what about the other alignment settings (castor & toe) compared to actuals and specs?

Are alignment settings for all 4 wheels within spec?

Believe Tire Rack has a "discussion forum" WRT tire brands and wear, sorted by make and model. IIRC, mileage ranges for Carreras was on the order of 6 to 10K miles on average for rears, though some got 15K or so, but that seemed to be the exception.

Buzz911S

I haven't had it on an alignment machine yet. But I will soon. Thanks for the info on Tire Rack... I'll check it out. I can't believe they wouldn't give you new tires after that! You must be a mellow guy. I would have been throwing tools around if I only got 4000 miles out of a set of $400 tires. My dealer said they were good for 20k and I'm going to hold him to it.

Does anyone know where to f ind the factory specs on this stuff?

Buzz

lawjdc

I have 6600 miles on PS2's - the rears have another 4mm to the wear bars. So it looks like I will get about 10,000 miles out of the rears. I will put on 305's when the 295's on the rear are replaced.

MJones

Front:
Toe uncompressed (total)
+5' ±5'
Toe difference angle at 20° lock
-1° 40' ±30'
Camber
-15' ±15'

REAR:
Toe per wheel
+10' ± 5'
max. difference, left to right
10'
Camber
-1° 10'± 15'
max difference, left to right
20'

Buzz911S

Thanks a million!! This will help immensly when I go to the dealer. Negative one degree? I think I have more than that.

Here's something scarey. My 26 Y.O. son and I had been to Daytona to meet some mutual friends for lunch. He drove up...ran through a couple of S turns very nicely.... then he slowed down. After lunch he gave me the keys to drive back home. I took a different route and we had a chance to let it rip down a wide 2 lane road in the middle of nowhere. It's about a 3 mile straight that gradually goes into a smooth right hand curve. From a roll in second gear I ran it up to 150mph and stayed there for a minute. As we approached the very slight right hander I downshifted to 5th and as we entered the turn, the left rear suspension started ... well, I don't know how to describe it. It was a "humping" up and down sensation. My son immediately said, what is that? I told him that is the same sensation I get when I go through the s's on the road to my house real fast. It's like the car is leaning over on the left rear axle and it is bouncing up and down. We agreed that it was a very uncomfortable feeling. He thought I was imagining it until today. What the heck could that be? It feels like the spring is bouncing.... like that tire has all the weight on it and then it bounces up. When it started doing that at the high speed we were driving it felt like the car was moving left to right .... almost like it was "fishtailing".... the only way I could stop that was to put my foot in it and drive through the wiggle. I don't know what's going on. The car is definitely humping the rear wheels and axles if taken through a nice turn at even a moterate speed say 75 or 80. The tires are not breaking loose... I'm stumped!

uzj100

Buzz-yeah, I am pretty mellow most of the time. I usually do my homework and find out what are considered to be "normal" parameters and do the best I can to verify them. In this case, the dealer telling you to expect 20K out of a set of rear tires on 911 is strectching the truth to say the least. These tires are like art gum erasers. But I think the tires wear rapidly when new, then the wear seems to slow a bit after that. In any case, if I got 10K miles out of the rears, I'd be fine with it. Why don't you make some connections with tire people that you respect in your area and have them check out the tires and see what they say? Also, are you maintaining the right pressures? I know it's an obvious question, but I make it a habit of checking miine cold once a week with a digital tire guage.

If you're alignment is within spec, and your pressures are too, then drive and enjoy. Maybe your Porsche dealer will suggest dialing in a bit more positive camber to help tire wear, but still keep the handling you want.

Please post back on here what you find out

MJSpeed

It sounds like the sway bar is detached (if the 997 has them) that's another thing that was common in the GT3's (loosening bolts on sway bars). As I suggested before, go in to your stealer, err dealer and have it re-aligned.

One other thing I forgot to mention before. As a former Formula driver, I myself had a bit of challenge adjusting to driving street cars on a track. I came from cars that weighed 1/3 as much with tyres that were wider and slicks to cars that weighed 3 times as much with tyres that were much harder and not slicks. I luckily have always been gentle on tyres but like many modern formula drivers, I'm a pig when it comes to brakes. That coupled with the weight and tyre difference and the fact that I break as late as possible everytime (bad formula car habit), I go through brakes like some people go through tyres!! (pun intended)

My point is that if you're not used to driving something whether it's a formula car, street car or especially a P-car with the engine out back you may (most likely) need to adjust your driving style and techniques or else your equipment will suffer and/or show your shortcomings more. By shortcomings I mean to that particular type of vehicle.

I'm not suggesting that you're doing everything wrong and that's the reason for the accelerated (perceived) tyre wear. However the fact that the driving techniques for a P-car are different from anything you may have driven as well as a mis-aligned car maybe the cause for all your woes.

Like I said get it re-aligned and we'll be able to start ruling things out.

Something needs to change and the first and easiest thing to change is the alignment. The hardest being driving style and techniques after all we're all great drivers!!!!

Einstein once said that the definition of insanity is doing the same thing over and over and expecting different results. Something has to be changed.

Oh and one more thing don't believe the stealer, gosh I keep doing that, I mean dealer!!

Buzz911S

Thanks for the input MJ... I'll get it to the dealer and get the thing aligned.

This is the first time I've noticed the fast occilation in the rear. It was a lateral movement back and forth so harsh that it was throwing us back and forth in the seats. That and the bumping rear suspension on hard cornering sure doesn't feel right to me. I'm getting pucker marks in the seats!

LastGT3

Buzz 911s - I think your tire wear is a little high...depending on your actual before alignment measurements
I run pretty high camber (3 deg frt and about 2.7 rear.) I wonder if your rear toe "dragging" is off (out) and dragging the inner part of the tire. FYI I have 10K km on my OEM PSII's (so 6,500 miles) and I have at least 1000 km of use left - ie my outer edge wears faster than the inner! - so something's weird for you. My agrressive alignement is causing me no problems, yet your milder alignmnet is causing excessive wear...weird.

Buzz911S

Thanks for the input.... I'm thinking the same thing. I need to get it checked out anyway. There's something strange going on with the rear suspension that I really don't like. The suspension is rebounding when I push it through a turn hard. Very unsettling and I'm thinking maybe dangerous.

Buzz

MJSpeed

Good thinking!

Again just make sure that your sway bars are on correctly.

What if it's PASM acting up, I don't know enough about the system to know what it feels like or what it's doing/or not doing...just a thought.

Please let us know what happened!

Buzz911S

Thanks MJSpeed... I"m calling the dealership now before I kill myself. The road I live on is a 2 mile straightaway that abruptly leads into a beautiful tight "S" turn. I just cannot resist burning through the S's at high speed,, and that is where I notice the rebounding most. I'll let you know what they come up with.

Buzz