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Gus Berges's Avatar
 
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Question Different tire sizes in the rear emergency?

Hello fellas,

Quick "emergency" question: not sure if the car has a limited slip on it or not (1991 964 Turbo), but assuming it did, would putting two different tire sizes in the rear burn it up in no time? I am talking about same rim size, but due to no tire available and immediate need to drive 300 miles, I was wondering if it would be OK to temporarily put a different tire size on either side of the car, say wearing 255/40 on driver's side and 295/30 on passenger' side. This will be 10 miles of street to get to the highway and the rest highway. Crazy, I know, but time is of the essence and no availability.

Thanks.

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Old 05-01-2012, 06:47 AM
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If you do have a limited slip diff., you will absolutely kill it driving 300 miles with different size rear wheel/tire combinations.

Mark
Old 05-01-2012, 07:50 AM
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Thanks for the confirmation Mark. Besides looking under the hood for the options sticker, the quick way to determine if a LSD is installed (without actually driving the car) is if the rear is raised and when in neutral, one tire spins in the opposite direction of the other, correct?
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Old 05-01-2012, 08:07 AM
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Hey there Gus,

Nope, with a limited slip both wheels turn in the same direction.

Mark
Old 05-01-2012, 09:28 AM
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Oops! Thanks! If no LSD installed, would something else break?
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Old 05-01-2012, 09:32 AM
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Hey there Gus,

If you have an open diff. you should be ok, but.....

I would still rather see you buy a couple of real cheapo tires, and then resell them, ounce you are home, but thats just what I would do if I was stuck in your position.

Good luck with your venture home.

Mark
Old 05-01-2012, 09:42 AM
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According to the tire size calculators (and that you're running 18's) the following is accurate-

255/40 have an outside diameter of 26 inches
295/30 have an outside diameter of 25 inches

There is a diff. of about 4.1%.............significant?
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Old 05-01-2012, 10:20 AM
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Another option, if you've lost one of your rear tires, might be to pull all 4 wheels and put the two matching front wheels onto the rear...and whatever combination you have left onto the front. Of course, be mellow since handling would be affected with a combination of 295/30 and the spare donut tire on the front.

Last summer I "popped" one of my stock sized rears about 4 miles from work. Drove in with the spare on, then proceeded to swap one of the front tires with the donut...to get at least reasonably close to the same tire size in the rear since I do have LSD. Drove 20 miles to home, and the LSD is still slipping in a limited fashion as far as I can tell.
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Old 05-01-2012, 10:29 AM
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Thanks guys. This is for my brother who is desperately looking for a tire in Miami and needs to drive to Palm Beach for his wedding on Friday...

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Old 05-01-2012, 10:46 AM
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