ca993twin

I've only had my 96 TT for about three months, so I haven't had any actual experience yet, but I've read over and over how the TTs "eat" rear tires in way less than 10,000 miles. While the TT is heavily rear-weight biased, it really isn't that heavy (about 2000 pounds total on the rear tires), and is riding on lots of rubber (285s or 295s in most cases).

I can think of these reasons why there may be a tire-wear issue:

1. tire-burning starts
2. very aggressive cornering
3. alignment calls for lots of toe
4. all the brands of rear tires use a very soft compound

Some of us rarely do 1 and 2, and I don't think 3 and 4 are true. What am I missing? Does the the tire fairy sneak into the garage at night and shave a little rear tire? Does everyone see this excessive tire wear?

Thanks

ruffy

I'm not too sure if any of these statements are founded, just a quick guess.

1.It would make good sense that the driving tires exert most of the engines torque... hence will probably wear a little faster. coupled with the weight hanging over the rear axle will affect the amount of wear.

2.The dynamic suspension alignment changes the toe and camber setting upon squat situations... probably does account for some more tire wear.

3.If the tire fairy comes around... she'd better be in tight spandex, looking like a race queen. Or she'll have a quick lesson in a citizens rights to bear arms

Rob O'Meara

The rear tyres run hot as they're so close to the engine. This accounts for some of the wear. However if you're getting 10,000 miles out of your rears then I would say you're lucky. The lowest I've had is 5k miles on relatively hard Bridgestone S-02. If you upgrade to Michelin Pilot Sport Cup tyres expect to get even less mileage.

Rob

Greg Fishman

Look at the negative camber on the rear tires. The factory dials in a lot and if you mostly do commuting type miles you will wear them on the inside edges very quickly.

If you are overly worried about tire wear you probably shouldn't be driving a Porsche, especially not a 993TT.

Rob,
Where in the world did you come up with the idea that engine heat affects the tire wear?

ca993twin

Greg,

Sorry if you misunderstood... I'm not griping about the tire wear; I want to understand WHY they wear so quickly. My S03s are not worn on the inside edges, they look uniformly worn to about 50%... and a performance alignment and corner weight was done shortly before I bought the car. I'm not sure when those tires were put on the car, but they look about the same as when I bought it, and I've put about 3000 miles on the car. Perhaps my tires are wearing better than others? Anyway, thanks for the ideas. Any others?

AndyGlaister

When I first got my car I had a new set of tires installed and got it aligned properly. These S03's have lasted 17000 miles on the backs and still look good (maybe down to 30%?). I drive about 30 miles high speed highway a day with the occasional autocross - I'm sure more aggressive corners and braking on my way to work might increase the wear, but I have to think than anyone getting less than 10,000 has an alignment or incorrect inflation issue.

1. Tire buring starts - with ABD as standard, AWD and our weak clutches? - I don't think this is a cause.
2. In America where you do find these sort of roads?? (I really miss English roads -sigh-)
3. Bet you alignment is the main reason.
4. Yes, the better the tire, the less it lasts, but I'm sure there are plenty of people like me who can get reasonable mileage on a 993TT, so this cannot be the factor.

Andy.

Anir

I always change tires way before the tread starts to show any significant wear, because the rubber hardens and gets "greasy" (i.e. loses its maximum grip). Maybe, the number of heat cycles has something to do with it. I do a fair number of DE's and mostly short distance driving. I also run lower pressures than recommended by the factory to maximize grip. Actually, how anyone can run 44 psi in the rear is beyond me.

Andy, a lot of folks that change tires with less than 10,000 miles have no alignment or inflation issue. They are simply more fussy. Even though your highway commutes are likely more gentle on tires, I suspect that you may not have noticed the loss in traction in your 17,000 mile tires because you've lost it gradually over a period of time.

Pete K

Andy,
I attended the NW/PCA tour Saturday and found some excellent roads for spirited driving. ;-)

Join us next time.

Pete

Rob O'Meara

The proximity of the engine and its oil ducts to the tyres increases the temperature of the tyres. This is good for grip, but reduces the life of the tyre. Obvious stuff.

Anir

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by Rob O'Meara:
<strong>The proximity of the engine and its oil ducts to the tyres increases the temperature of the tyres. This is good for grip, but reduces the life of the tyre. Obvious stuff.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">So there, Greg. <img border="0" title="" alt="[Wink]" src="wink.gif" />

Rob, on the surface, this appears reasonable, but it also gets pretty hot near the oil cooler. Have you ever placed your hand on the right front fender after a good run? It's at least as hot as either of the rear fenders.

ScottMellor

I had 14,000 on my So-2s and they were 50% worn down on both front and rear. I let Anirs' post psych me out into believing that they were losing grip and replaced with them with P-Zero's

Rob O'Meara

Yes Anir, it's amazing how hot the fenders get after a spirited drive. It's great if you're popping into the supermarket for a couple of things. You have your very own F1 style tire-heaters keeping the rubber nice and sticky for the drive home.

I'm not really saying this phenomenon *excessively* impacts tire wear, just that it's a small factor. BTW I don't like being patronised, however necessary this may be for a "guru".

Rob

Anir

Rob,

Don't kid yourself, Rob. You know as much as any guru around here.

You may have a point about the engine heat's small influence on tire hardening. Makes sense.

Rob O'Meara

Thanks Anir, can't wait to hear about your PSS9 project. It's the next thing on my shopping list...

pwrsurg

Hi Anir. What pressures do you run front and rear? I have a just-purchased 96 993tt and am using the recommended 36 / 44 pressures. So far I am just driving about 10 miles on 4 lane but can get up to speed about anytime I want to.

Tom