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

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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

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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.

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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

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I was thinking of doing this very often on my next set!! Very good idea.

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

That ^ will work on symmetrical tires, but NOT with asymmetrical tires. Asymmetrical tires are constructed in such a way that there is a defined outside and inside edge of the tire. Also, the groves in some tires are constructed to take water away from the center of the tire and move it to the edge. Mounting them "back wards" would not be a good thing in either of these instances. EDIT: Damn Tom, you beat me to it!

I vote for toe, but I'm interested in seeing the before and after numbers after you have it inspected.

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We can get this thread closed in a hurry with this comment..

Your tire wear certainly is indicative of too much camber. I do not think that you have a toe issue as this would tend to wear more than just the inside edge. You might want to check out the Michelin sport tires as for some reason they seem to resist this wear a bit more. Just me .02 cents Erik Johnson [phone removed] cell

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Yeah, what he said! I would suggest having your alignment set more neutral. Many do. It cuts down a bit on the sharpness of the steering, but greatly improves tire life. This is also a great opportunity to tell EVERYONE it's time to inspect their tires. I know it's not easy to get down there and look, but that's the reason these surprises happen.

Thanks again for the advice guys. Macster, you reminded me that aroung the time I had the tires replaced, I hit a rock/pothole that damaged my passenger side rear wheel. I had to have the barrel straightened. I wonder if that damage was enough to knock the alignment off. Damon, good advice on checking the tires more frequently. I went for a spirited drive on Saturday that could have had a bad ending. After doing a little research, I am going to switch to Hankook Ventus V-12 Evo tires. They are pretty hard to beat at $200 each for the rears. In a Car and Driver test of summer performance tires, they came in second, out of 9 tires.

...I think your camber is fine. The problem is you aren't cornering hard enough. Cheers,

Allan, I like your analysis of the problem. I have never been accused of driving too slow, but I think you might be right. My wife might disagree...I will be sure and tell her that one of the Porsche suspension experts on Rennlist (you are an expert in my book because you drive a sweet looking GT3) suggested that my excessive tire wear was from driving too slow around the corners.

lol! My wife can't be in my car for more than a block without getting sick. About that pothole you hit...anytime you get an impact on the wheel that is strong enough to bend it, you can probably count on the alignment getting knocked out. I've found at the track if I spin and mow the lawn, sometimes that's enough to throw off the alignment. Just enough force applied in the wrong direction can move things. Cheers,

Topaz...I just got these tires put on Monday! I paid $1100 all in buying them from TireRack. Then $350 all in for installation and alignment. Full alignment for $150 is really cheap! Looks like you got a good price, just make sure they give you a print out of the setup they did. As for the Hankooks, they are nice. Pretty grippy at low speeds ( <100kph) absorb bumps better than the Michelin's I had on it before. My Michelin's were worn to the threads on the inside edge, just like the OP....so I asked the shop to take a little of the camber out for street use. He basically reset the alignment to stock position. He did this with me sitting in the car and a 30lb propane tank in the boot (since I brought the car in with an empty gas tank) It tracks very straight and true. Turn in is nice.......BUT....the car is very washy at anything about 150 kph. The back kinda floats a bit when cornering....even loooong, low radius turns. I actually had the back start to drift out on my a couple times. Not confidence inspiring!! Now is that the tires or the alignement? I'm thinking alignment as there are plenty of other people running the hankooks that are not expressing this rear end lightness at high speed. So do I want track tight setup that will eat my rears in no time for the (very) occasional high speed run or flat alignment? Prolly going to keep it as is for now.

Hey seanmcr6, I just checked out TireRack.com and it gives me a total of $640 for the tires and $140 for shipping. How come you paid $1100 all in?

$640 for the tires $230 for shipping (remember I'm waayy up north) $37 GST $44 duties $30 brokerage fee $16 provincial tire fee Total $996 USD I think my visa turned that into $1060...something like that

Damn we get taxed on everything man! My price still came to a little bit lower... I might pull the trigger on these, still thinking....

If you can get a cheaper price locally, then definitely buy it. I tried calling 10 different tire shops to buy these...and most of them said they couldn't even get them (they were all on Hankook's site as distributors) and the ones that could were much more expensive. The guy I had do the install and alignment asked me how much I paid and when I told him, he said he couldn't possibly sell them to me at that price. It was like a hair above his cost! Canadian dealers get screwed on pricing...on everything. Car parts, motorcycle parts, photography gear. It's sad. I don't know how they compete. Saying that, Tirerack was an absolute dream to order from.The have all those items I listed above covered in their price. So you pay them and that's it. No dealing with UPS bs, or delays in brokerage, etc.

I just had the Sumitomo HTR ZIII 295/30/18 tires installed. I drove it for a couple miles and the tires felt fine. I had an alignment done. I made the mistake of not specifying the alignment settings and they set it to stock. It is now scary to drive. The rear end feels squirrely. My before settings on the back were -2.2 and -2.4 degrees of camber. I ate through a set of back tires in less than 5,000 miles. The rear is now set at -1.2 degrees of camber on each side. Toe was within stock perameters. My fronts are at -.8 and -.5 degrees. I am taking it back tomorrow to have the camber settings changed...Any suggestions for how much negative camber to run front and rear? (lots of spirited driving on country roads and hopefully a couple track days)

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For a good compromise alignment, you coud run around -2 on the front, and just under -2 in the rear [around -1.7 or so]. That will give you decent performance on the track and won't chew through tires that fast. Make sure you don't get a ton of toe in for the rear. With the Sumis, you will get better wear. -td

I eat rears before 5k miles, too. A lowered suspension will do that (OP, you have PSS9's, right?), and a widebody will further exacerbate that, apparently. I've resorted to running the Sumis, so at least I don't cringe as much when it's time to replace them.

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We can send Obama your way ...you ain't seen nothin'

TD and ED, thanks for the advice guys. I would rather go through tires every 5,000 miles than have it handle like it does now. 1.7 on the back sounds about right. The Sumis are defintely less painful. Pete, I voted for the other guy.

Isn't the car closer to track alignment being closer to neutral on the toe in front and rear? More squirly that way but.......