[Kim]

What kind of wear do you guys get on rear tires (not racing, just road driving). I put a new set of 245/45 x 16" on about 14,000 km ago (Yokohama AVS ES 100) and they are almost worn out! Front tires have 38,000 km and still have lots of tread left. They are howling so much I thought the car must have a failed rear wheel bearing.

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[flash]

i'd have your alignment checked - rear thrust angles and toe sets being out, as little as two tenths of a degree, can chew tires incredibly fast



a full 4 wheel alignment, including ride height, is something that should be done, on average, once a year anyway



i think we are going to start seeing odd tire wear pop up a lot in the near future - most everyone has original bushings in the control arms - these get worn and allow a lot of play, which causes tire wear

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[Bob Kovacs]

When I bought my car, it had a new set of Bridgestone something-or-others on it. Within 10,000 miles, the rear was making noise that I thought was a wheel or pinion bearing, only to see that the rear tires were bald in the middle. I had kept the tires inflated to 36 psi. The front tires had plenty of tread left. Since my tires got bald in the middle (and no wisecracks about the tires resembling the owner!), I assume the pressure was too high.



I replaced the Bridgestones with Continental ContiExtremeContact tires (I have 17-inch rims) and keep them inflated to 34 psi. After 20,000 miles, the Continentals are quiet, handle well and still have plenty of tread. I will definitely buy them again when the time comes.



I don't race the car at all, just street driving and relatively tame street driving at that. These Continentals clearly have no problem with that and will handle lots more. The company makes a big deal about the tire's compound being designed to handle sloppy weather, including snow. However, my 968 sees snow only through the window of the garage.



--Bob

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[RPM]

There is no doubt that some tires wear more quickly than others, particularly turning noisy early in their tread life. However, premature wear patterns are a result of bad alignment, improper tire pressure, damaged suspension, or a combination. Some newer Porsches, particluarly some of the 996 series, wear rear tires quickly. This is not the case with the 924/944/968 series. The inherent balance of the car is a boon to tire longevity. 36 psi is the factory recommendation. I run at 34 for comfort, but have seen no undue wear patterns as a result in three sets of tires - AVS db/Kumho Ecsta (big mistake!)/Bridgestone RE750 Potenzas.



The problems you describe are alignment most likely. These cars are hard to align for the average tire shop. They just don't have the experience, nor are they willing to spend the time to get it right. When I bought my old S2 it had receipts for numerous alignments at seemingly reputable shops around town and yet was ripping up tires. I took the car to a performance tire specialist recommended by the local PCA region and he got the alignment straight, possibly for the first time in years. After that, no problems.

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[Anchorman]

Before I changed from the same Yokohamas (18"), I had nearly 30k miles on them and plenty of tread left - and that's including 3 2-day DE sessions at Watkins Glen. I thought they'd be good for at least 50k miles.

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[KRAG50]

On the subject of alignment, Is anyone for or against a home alignment using a SMART CAMBER AND STRING GAGE set-up. I see this done at SCCA races all the time. It must have some advantages such as allowing small change to improve performance, and must be fairly accurate to satisfy these racers. <img src="/forum/images/smilies/968/smile.gif" class="smilie" alt="" />

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[flash]

this car has been the most fickle car i've ever dealt with on alignment, and it gets even more so with a modified suspension - i am now at the point that a tenth of a degree makes a significant difference in handling, and i'm still set up as a street car



i thought about one of those setups, but figured there was no way i could get accurate enough on this car

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[RPM]

My alignment guru, who sets up lots of track and race cars, spent nearly 2 hours getting my car straight. Don't try this at home folks!

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[KRAG50]

You guys seem super sensitive as to how your 968 handles. What about the average joe? In my case I'm going to need to run over 100 miles one way, to find a "guru" and most likely stay overnight. What about a basic adjustment after the mods I'm doing, springs, shocks, sway-bars, bushings, brakes, and strut brace, just to get it to someone I trust.

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[RPM]

With that qualification and need, the string process would be fine for 100 miles. You will definitely want a good alignment following suspension mods.

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[flash]

agreed



there are some sample setups in a thread here entitle "alignment specs"



things to make sure your alignment guy has: the eccentric tool, and a thin 36mm wrench

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[Kim]

        The car is being aligned on Thursday. In anticipation, and knowing that I need four new tires, I took all the wheels off to completely clean and wax them inside and out. This was a three hour project. Thinking back to Newtown, I remembered the the rear wheels on all of your cars seemed to be more "outboard" than the ones on my car. The rear wheels are 16" diamter x 9" wide and they have on the side of them neat the valve a stamp that says 9/70. The front wheels , which are 7", have a stamp that says 7/55 (my other car also has the same stamp). Could this be an offset number that is not correct for the car? If any of you are running 16x9's what is your offset? These are Porsche wheels and I saw at least some of you having the same kind. Pics aren't great but may help.



Flash, I downloaded your alignments specs and will take them to the Porsche shop with me. May car hasn't any front brace - can I use any of the specs that you posted?

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[flash]

only the stock ones really - i wouldn't vary from that much - maybe a touch less front toe and a touch more front camber, but that's it



without a brace, there is really too much camber change going on to run any of those other specs without getting more tire wear and some odd handling characteristics

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[Anchorman]

Kim, I've never heard of anyone having a rear wheel with a 70 offset. Definitely puts the wheel/tire far "inside". My winter wheels are 16" and 8" wide in the rear with a 52 offset.

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[Kim]

Archorman - my 16 x 8 on my cab are also stamped with a 52. Its these 9 inch ones with the 70.

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[bob blackwell]

Kim, those numbers are the offset numbers and they appear to be for a 911. Looking at the picture of your wheel it looks just like the 993 Targa wheel. You will probably be happier with wheels which have the 968 offset. Good luck, Bob Blackwell.

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