Tire Wear Inside Rear Tires

[slahti]

2006 997S - Coupe

78k MIles

I have a pair of pretty decent Bridgestone Potenza RE050A on the rear. I have put about 10k on them and the inner thread is showing

through, seems every 10K the rears need replacing I do drive a little agressive but no too crazy.

Do 997s often lose alignment? or for a semi-agressive driver is this to be expected ?

[Loren]

If you are a spirited driver (like me) you will be lucky to get more than 10-15K out of rear tires. So if you are - that is normal.

[logray]

If the setup on the rears has a lot of negative camber and you drive them hard 10k is probably not that far off... 15 to 20k would be pushing it for a tire like this.

I have (and love) the same tires and hope they last 15k.

[slahti]

"Spirited" ... I have to tell my Wife that one {:-)

BIG THANKS AS USUAL You always help out.

If you are a spirited driver (like me) you will be lucky to get more than 10-15K out of rear tires. So if you are - that is normal.

[slahti]

"If the setup on the rears has a lot of negative camber"

So can this be adjusted? .. I have probably 3/4 inch or more tread on the outer of the tires the inners are BOTH showing metal..

If the setup on the rears has a lot of negative camber and you drive them hard 10k is probably not that far off... 15 to 20k would be pushing it for a tire like this.

I have (and love) the same tires and hope they last 15k.

[Loren]

Not without affecting handling.

If you look at Cup Cars they about 1-2 degrees negative - front and rear!

[halsyknox]

"If the setup on the rears has a lot of negative camber"

So can this be adjusted? .. I have probably 3/4 inch or more tread on the outer of the tires the inners are BOTH showing metal..

If the setup on the rears has a lot of negative camber and you drive them hard 10k is probably not that far off... 15 to 20k would be pushing it for a tire like this.

I have (and love) the same tires and hope they last 15k.

I don't drive mine on the track so when I got a new set of tires I told the alignment shop to split the difference between P spec and flat for rear camber. I'm sure that goes against everything porsche does but it is rediculous having to replace a tire due to 1% of it wearing out. I've driven as fast as I want on the street and have felt no instability or problems with the camber less than stock. On the street, you probably couldn't feel a difference even if they were absolutely flat. But what do I know, Porsche goes as far as specifying tire brand and model, let alone size.

[PAULSPEED]

I had my car aligned for track use. They put very

small shims in the bottom rear a-arms. This stopped the

car pushing when entering a high speed turn.

The point is the rear insides still wear out even if I did not

do anything with the alignment.

I guess you could call it weight shift engineering. The only solution

would be a straight axle, but then the car would drive like a truck.

Paul

[tomnash]

Given the gazillion useless warnings in the Porsche (and other car) manuals, one very useful warning that Porsche should give to new owners is exactly about this issue. The camber is set up negative for good handling, but this results in much more rapid wear on the inside. This is not intuitively obvious to a new owner!

So, an innocent owner who conscientiously checks the tread on the outside and center where it is easily visible, can have severe wear on the inside and a surprise blow out. Exactly this happened to me at a particularly remote (cellphone dead) location in central California, a 3 hour tow to Bakersfield, on my first set of tires 4 years ago.

Check the wear on the inside of the rears!

[slahti]

Kind of embarrassing, but yea same thing happened to me two years ago. I had no idea, luckily I was only going like 20 mph :-)

Seeing all the tread on the outside figured I was ok.

Well... finally a complaint to PORSCHE ... They should let us NON-GERMANS know these things.

In closing,

Thanks for all the help here fellas.

Given the gazillion useless warnings in the Porsche (and other car) manuals, one very useful warning that Porsche should give to new owners is exactly about this issue. The camber is set up negative for good handling, but this results in much more rapid wear on the inside. This is not intuitively obvious to a new owner!

So, an innocent owner who conscientiously checks the tread on the outside and center where it is easily visible, can have severe wear on the inside and a surprise blow out. Exactly this happened to me at a particularly remote (cellphone dead) location in central California, a 3 hour tow to Bakersfield, on my first set of tires 4 years ago.

Check the wear on the inside of the rears!

[tomnash]

Thinking about this some more, I believe it is correct that if you really corner hard consistently and frequently, as on a track, your tire wear will be more even than for normal street driving. The whole point of the negative camber, if I understand correctly, is to get more rubber flat onto the pavement during hard cornering. The camber compensates for the roll of the car.

On the street dominated by straight ahead driving the negative camber puts more force on the insides, wearing them faster. If used for continuous cornering on a track, the tires may wear quicker but the wear will be more even.

Correct me if I have this wrong.

[PAULSPEED]

The goal on the track is to have the same temperature across

the entire tire.

You will let out 2 psi air at the track to get this right. After one lap the tires are up

to temperature and then you verify the tempertures the minute you come off the

track.

I never put nitrogen in the tires but I heared that you want to purge the tire first before you add

the nitrogen.

Paul

[rob545]

Thinking about this some more, I believe it is correct that if you really corner hard consistently and frequently, as on a track, your tire wear will be more even than for normal street driving. The whole point of the negative camber, if I understand correctly, is to get more rubber flat onto the pavement during hard cornering. The camber compensates for the roll of the car.

On the street dominated by straight ahead driving the negative camber puts more force on the insides, wearing them faster. If used for continuous cornering on a track, the tires may wear quicker but the wear will be more even.

Correct me if I have this wrong.

I think you have it right on the money. So to take it to its next logical conclusion, we all need to concetrate on having more track days, and increasing the intensity of our "spirited" driving, in order to make the most complete use of our automotive resources. :jump:

[slahti]

GREAT HELP GUYS. THANKS A MILLION!! caps off :-)

[slahti]

Wanted to ask one final question seems semi-relevant to this thread, the door states PSI 44 rear 37 front. I have heard some folks run a little less what are the thoughts here?

[tomnash]

Wanted to ask one final question seems semi-relevant to this thread, the door states PSI 44 rear 37 front. I have heard some folks run a little less what are the thoughts here?

There is usually a second sticker that indicates a lower PSI is acceptable (desirable?) for half loaded conditions (as defined in the manual). I suspect this improves handling marginally, as suggested in PAULSPEED's post where PSIs are reduced on the track.

[Loren]

I suggest reading the following tire pressure tips:

Air Pressure: When and How to Set

[PAULSPEED]

Here is my car on Infineon (Sears Point) raceway

going thru turn 7. You enter at high speed, brake hard,

make a hard right hand 180 degree turn, and accelerate

hard leaving the turn.

Note in the picture that you can see light under the right front tire.

This tire was higher in the air before I installed a bigger rear

stabilizer bar. The bigger bar made the car act more like

a slot car.

Paul

[tomnash]

I suggest reading the following tire pressure tips:

Air Pressure: When and How to Set

Loren, where can we find those tips? If this was to be a link, it is missing. I tried a search...

[Loren]

Sorry - the link is now fixed.

[tito_gsx]

Paulspeed, I like your picture, is that stock suspension with bigger rear bar? Sorry to go off topic but am curious if that helped handling vs. stock