Excessive Tire Wear
 

A couple days ago, my wife and I went for a drive in the Porsche on a local country road. The ride was pretty rough, so I decided it was time to change the settings on my PSS9s to something a little softer...from 2/3 to 9/9.

While I had my car up on the ramps, I made an unpleasant discovery. About 13 months ago, I bought a new set of rear tires. They are Continental Sport Contact 2 tires, in size 295/30/18, mounted on 10.5 inch wide Kinesis wheels. I bought them from Tire Rack for $320 each. They now have 4,411 miles on them.

This is my second 996 and I know that they eat rear tires, but this is ridiculous. The right side had already gone through one layer of steel belt. The tires were through to the wear bars on the inner 2/3 of both tires. Is my problem too much negative camber, too much width on the tires, or too heavy a right foot?

Needless to say, I will not be buying another pair of Continentals at $320 each. I am considering BF Goodrich T/A KDW 2 tires in size 285/30/18. Any advice?

First of all, I'd check your alignment. Based on the tire wear, i'd guess that you have too much negative camber for the type of driving you are doing.

Secondly, it's a bad idea to mix tire brands front to rear, so either go through another set of Conti's on the rear until your fronts are gone, or replace the whole set. I run Bridgestone RE050A's on my 997 and am very happy with them. I think they will be a bit charper than the Conti's, and are probably a better tire. Or you could go real low budget and try Sumitomos. I've never used them, but lots of people seem to like them.

At the end of the day though get used to going through rear tires. Maybe not as fast as this set went, but still, expect to be enjoying new rubber on a regular basis.

You could go with Conti Extreme Contact DWs (or with Sumitomo HTR ZIII which every seems to like)

Mfletch:
Mglobes advice on not mixing tire brands in "spot on" as any mixing can cause issues with PASM, etc.,...having said that, I used to run Conti's, would usually get about 9,000 miles out of the rears, depending on how much time at the track. At the end of hte season last year I debated about a new set of sneakers.........Coni's? or try Sumitomo's? Whether "real low budget" or not, they are pretty damn good, especially when you look at the price. I put a spike in the sidewall after only 100 miles on the ledt rear...the sneaker was trashed........replacement wasn't so painful.......could have been a Conti or Michelin,....yikes.......a whole 2nd set of Sumitomos can be had for the roice of one set of Conti's.......my advice, if you look at the Sumitomo's......go with the HTR Z III series...not N spce rated, but pretty damn good rubber and impressive at the track, too. Just my humble .02.
R\
Scott

As Mike said, check your alignment. That wear pattern is indicative of a track alignment (too much negative camber). You might also have too much toe in. Also, is your car lowered?

IMO, you should just get a set of Sumitomos. I ran them on my old 996, and now I have them on my GT3 for the street. With my agressive alignment, I don't feel bad about eating through them every year. As for track use, I respectfully disagree that they are any good. They are over 10 seconds a lap slower on my car. That's an eternity...

-td

Alignment. Uneven wear across tread face almost always alignment. I have the most experience with my Boxster (234K miles and you know I've gone through some tires) and have on occasion run the rear tires at max allowable negative camber and tire life has been unexpected. Alignment shop -- Custom Alignment in Mountain View CA -- told me this would be the case when I questioned one of its very knowledgeable techs about leaving the rear camber at the high negative setting.

In all cases where rear tire wear has been uneven across tread faces the rear toe in has been the setting that the before and after readings indicate was the culprit.

Either one rear wheel's toe in off or both off.

Heavier wear of the right rear tire is normal and results from lack of LSD. Since in the USA most turns are to the right and the sharpest turns are to the right, the right rear wears the fastest.

That the right rear tire wore so much more than the left rear suggests to me you have a heavy throttle foot.

In the case of my Turbo, running Continentals, with proper alignment I can get 15K miles from the rear tires. Tire wear across the face of the tread is quite even and from side to side is quite even as well. Since I know hot footing it around right hand corners eats the right rear tire I avoid doing this as much as possible.

In one case rear tire life was just 8K miles. A new set of rear tires and another alignment -- at a local Porsche dealer and not at a more distance one that did the then currrent alignment -- found the alignment out of spec. After the ;local Porsche service department did the proper alignment rear tire life once again increased to around 15K miles.

Proper and correct tire alignment critical for getting the most service life out the tires.

When you take car in for new tires and an alignment, have gas tank full, car empty of all junk, and if fitted, have the spare tire and tool kit installed and secured properly.

BTW, some places place some weight in the driver's seat and some don't. I have had my Boxster aligned both ways and I can't tell the difference. Tire life and tire wear appears unaffected.

I can't help you regarding running different tires front and rear. Porsche advises against doing this and I never have tried it. I run N rated tires of the same brand/speed rating/hardness/N number/etc on my Porsches.

Sincerely,

Macster.

Thanks for taking the time to post the advice guys. I really appreciate it.
Mike, I'm sure that you are correct about the alignment problem. My first 996 had an alignment problem that caused it to also eat rear tires. It turned out that it was a bent rear control(?) arm caused by the tire store jacking the car up under the alloy arm. Great way to guarantee the need for another set of tires in short order.
Scott and Mike, thanks for the advice on mixing tires.
TD, my car is significantly lower than stock. I hope that is not the cause of too much negative camber.
Macster, I have a limited slip diff. on my car. I checked with my old clutch and tires and it appears to be working properly...two nice even patches of burned rubber on take-off. Thanks for the advice on the alignment. I will be visiting the dealer as soon as I get new tires. The car is parked until I get them.

If you have LSD then the heavier wear on the right side is due to its alignment.

Once with my Boxster I misjudged how close to a curb I was and brushed -- well more than brushed -- the right rear wheel against the curb. It was a glancing blow that didn't do any significant damage to the tire's sidewall or the wheel.

I continued to drive the car and it felt ok. But the right rear tire wore faster than the left. I was aware of the possibility of the right rear wearing faster due to lack of LSD -- which my Boxster did not have -- and I avoided the type of driving that would result in excessive right rear tire wear. I drive my Boxster a lot (averaging nearly 30K per year) and long tire life saves me operating costs so I strive to maximize tire life.

Anyhow, when it came time to replace the tires I had an alignment done and sure enough the right rear toe-in was out more than the left rear toe-in.

Almost always when I take my cars in for an alignment I ask for and get a printout of the before and after alignment settings. I lke to study them and see just what was wrong, out of alignment, and correlate this to the observed tire wear.

Sincerely,

Macster.

Mark,

You can buy a new set of sumis for the price of two contis rears. sell the conti fronts and be done with it. these tires are plenty good for street driving.

You need to take a look at your tires once in a while.
You got close to a dangerous situation there!!!

Is there any extra damage that can occur while driving with tires in those condition? Would it affect the wheel bearings or control arms or anything else?

I'm currently looking for new tires and I'm really not sure what to pick.

I got a quote for some Hankook Ventuce V12's for $1300 CAD. Alighnment tire install/balancing is only $130.

But I have no real experience with those tires... So my shopping continues for now.

User error. Too much negative camber for 'actual' use. Try 0.0 to -0.5 degrees camber for street use

Make sure you tell the alignment shop exactly what settings you want, other wise you can get anything and may end up with problems again.

Think of all the lost traction you are experiencing driving on only 1/4 of the tire width. Wonder how sticky those steel belts are?

Another tip: Keep a close eye on inside rear tire wear and when the inside starts to show more wear than the outside, take it to your friendly neighborhood tire store and have them flip them on the rim, ie. remount the tires in such a way that the inside ends up on the outside and the other way around. In some cases they do it for free, and in a worst case scenario they charge you $15-20 per tire for (re)mounting and balancing.

JP

I was thinking of doing this very often on my next set!!

Very good idea.

I would be a little nervous about flipping asymmetrical tires. [FWIW, HRT Z IIIs are asymmetrical, and the IIs are directional.]

-td