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Old 08-14-2006, 07:39 AM   #1
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Unhappy Help Tires/Allingment/Mix&Match

Hi all, the family is calling me motor-man these days. I had a one day conference in Vermont this weekend and I decided to drive, yikes. I left on Friday from Virginia, 800 miles and 13 hours later I was in Vermont. Did the conference on Saturday, got in the car on Sunday, 13 hours and 800 miles later I was home.... I slept in a little this morning.

All this driving has been eating away an my 2000 2.7L Boxster I got a few months ago. It looks like I am due for rear tires for my 17" factory wheels. I have heard the stories about the tire-eating ability of the car and now the reality of the cost is intimidating. I have Pirelli's on the car now and I like them, but really have nothing to compare them to. I have noticed that they make more noise than I would like, so I am looking for a more quiet tire. Also, I have wanted to try Michelin's (ouch) at least once on the car.

The front tires still have some miles on them, I suspect they were put on at the same time as the rears as a set (I have no records), so I am planning on replacing just the rears. At first I wanted to put Pirelli's on the rear to match the front, but my local Porsche dealer said it would not be a big deal to put Michellin's in the back and keep the Pirelli's on the front and when the front Perilli's wear out, just replace them and I will be running all Michellin's. The dealer says the Michellin's are only 10.00 a tire more than the Pirelli's (290.00 per rear, mounted and balanced for Michellin's).

The other point is allingment, it is clear from looking at the wear pattern from the rear tires, there are allingment issues. Because of the lack of maintenance the car got from the first two owners, I suspect it has never had an allingment done. My local Porsche dealer says it takes them 3-4 hours to do allingment on all wheels, which I would like to get done when I get the new rear tires. So much for the background, here are my questions:

1. Is there a problem with mixing tires, older Pirelli's in the front, till they wear out and new Michellin's in the rear?

2. Why does it take them so long to do the allingment (90.00/hour labor), and can the Porsche dealer do anything in the allingment process that my local "jack-of-cars" local mechanic cannot?


Any addition comments on tires/allingment issues are welcome, thanks,

Ed

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Old 08-14-2006, 08:51 AM   #2
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Hi,

Mismatching tires front/rear won't cause the car to blow up, but the tires have different compounds, carcass construction, tread blocks, sidewall flex and varied characteristics. You may experience annoying handling, localized noise (1 axle louder than the other), wet traction issues, afterall, they are different tires - a mismatch. I would strongly advise against it.

Frankly, I'm very surprised a Porsche Dealer would endorse such a move. Tires are consumables and part of the game, as expensive as they are, you gotta pay-to-play.

Even changing one axle with identical tires can cause issues because of the difference in tread depths and tire flexibility between the new and the used ones on the opposite axle, but to a much lesser extent.

My recommendation is to either stick with the Pirellis or swap them all out. Absent that, be prepared to ditch the fronts in favor of a set of the new rears in short order when you experience some of the things mentioned.

Also, an alignment should not take anywhere near 4 hours. Don't give it to the dealer as this is not their specialty. Instead, take it to a qulaity, competant alignment shop specializing in Sports Cars in general or Porsches specifically. It'll be cheaper and the job will be done better. Be sure to get a 4-wheel, dynamic balance (Hunter 97XX series machine) prior to the alignment to insure getting everything spot-on. Hope this helps...

Happy Motoring!... Jim'99
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Old 08-14-2006, 12:26 PM   #3
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Have you done any research on tires yet? A few months on a set of worn/wearing out tires isn't much to go on. I certainly appreciate that many here have no problem spending $300.00 on a tire. However, I doubt that most people truly get the most out of that money.

There are definately cheaper tires out there - and better tires for the money. Please check out Tire Rack online before spending so much of your hard earned money on some stealership tires. I don't think you'll be disappointed.
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Old 08-15-2006, 07:13 AM   #4
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New Tires

Thanks all, for the advice. I have decided to go with all 4 Michellin's, I know it is pricey, but I want to see for myself how they ride. Does anyone know if the front pair of Pirelli's I will be taking off are worth saving? They have a fair amount of tread left, thanks,

Ed

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Old 08-15-2006, 07:34 AM   #5
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Does anyone know if the front pair of Pirelli's I will be taking off are worth saving? They have a fair amount of tread left, thanks.

Not an expert but my common sense suggest keeping the front Pirellis. As the new rear Michelins will wear out faster than the new fronts, you may want to replace them with new rear Pirellis which will match the old front Pirellis. So potentially you could switch between new Michelin and Pirelli at the rear (as you wear them out faster than the fronts) and always have a matching front pair for each rear pair. Could have said this with much less words but English is not my native language so pls bear with me.
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Old 08-15-2006, 08:28 AM   #6
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edevlin, you posted that from the wear bars on the back, it looked like the car was out of alignment. Note that on our cars, the rear wheels are intentionally aligned with quite a bit of negative camber, making the rears look like this:

/----\ <-- pretty nice ascii artwork, huh?

This alignment setup makes it very difficult for the back end to break loose under heavy cornering, but wears the insides of the tires far faster than the outside.

On my last set of tires, I had Discount Tire knock the rubber off the back rims and flip it around so the inside edge became the outside edge of the other side of the car. This is the only way one can "rotate" unidirectional tires. That made them last about 12k, but you must do it every 2k or so or the tread will be too uneven for safe driving.

And while I'm commenting, I'd keep those front Pirelli's. Considering replacement is the answer for a tire with a nail or screw in it, a spare pair of front tires is mighty nice to have in the garage when you don't have the cash for two new tires that match on the front... I've never been able to find a replacement tire with the identical tread pattern when I needed one... they change them every year it seems.
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Last edited by RandallNeighbour; 08-15-2006 at 08:31 AM.
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Old 08-15-2006, 12:36 PM   #7
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Hi,

Edevlin - Ditch the used tires!

Tires are only safe for about 4 years regardless of treadwear. This is because their compounds harden, they lose grip exponentially and lose their ability to shed Heat - the #1 Enemy of High Performance Tires.

Also, your tires start to Dry Rot the minute they leave the factory. This process is slow, but steady and will accelerate once the Tires are unmounted.

By the time you'd think of reusing them, they'd be unsafe, would last under 2k mi. (wear will accelerate once they've been set aside and harden), would probably leak against the aluminum rim, be awful in the wet, noisy, etc.

Remember, Tires are much cheaper than Sheet Metal Repair (your's and the other guy's) and People Repair. Like I said earlier - you gotta Pay to Play...

Happy Motoring!... Jim'99
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Old 08-15-2006, 01:50 PM   #8
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Quote:
Originally Posted by edevlin
My local Porsche dealer says it takes them 3-4 hours to do allingment on all wheels....

2. Why does it take them so long to do the allingment (90.00/hour labor), and can the Porsche dealer do anything in the allingment process that my local "jack-of-cars" local mechanic cannot?
this car is cake to align; i have done several myself. it takes less than one hour. any reputable shop with one of the NEW hunter machines can do the job quite quickly and every bit as well as the dealer. make sure you have them print you the initial alignment values and the final values (the Hunter machines print a report).

the suspension on these cars is highly adjustable and designed so that this can be easily performed. i know our local dealers charge $180 for a 4-wheel alignment (atlanta area). private shops should be able to do it for under $100.
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Old 10-17-2006, 07:04 PM   #9
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Has anyone tried reducing the camber on all 4 wheels to reduce tire wear? If so, how did it change the handling?
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Old 10-17-2006, 07:06 PM   #10
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i drive pretty hard, so i had to increase camber to reduce tire wear....go figure.
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Old 10-17-2006, 09:00 PM   #11
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I had mine aligned to factory specs and it still takes the inside of all four tires down to the belts while the outside still has over 50% of the tread left!!!!
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Old 10-18-2006, 08:03 AM   #12
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If you are in a pinch, you can get away with mismatched tires (never do mismatched on the same axle, NEVER!) but like was mentioned you will most likely see some funky handling changes and in some cases it could be unsafe. Keep in mind that not only is the tire going to have different handling characteristics, but your fronts will have some aging issues. If it were me and I wasn't going to buy 4 tires I would replace the rears with identical or comparable Pirellis.
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Old 10-18-2006, 09:55 AM   #13
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edevlin just got a new set of wheels and Falken tires, so this thread's old news!

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