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Real World Tire Presure

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Old 11-01-2010, 02:24 PM
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Resu Deretsiger
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Real World Tire Presure

I have a 09GT with the OEM tires on it with about 30k miles.
A few weeks back I was in to the dealer for an oil change and
tire rotation. They also bumped up the tire pressure to 36 from the
32 it has been from day one stating it should really be 36 not the 32
I had. My dealer has done a oil change every 3k and rotation every 6k
and this is the first time they decided to up it to 36. The door jam on the
car says "32".

So why all the fuss on my part.

The first time I drove my RX8 in the rain(after the change) I spun it out on a tight
right hand 210 degree on ramp that I have used almost everyday for 10 years.
The last year in my RX8.

I have never even once in my 40 years of driving spun a car, any car.

I can't really say this wasn't my fault, I was doing the driving, yet I wonder
about the extra 4 pounds and how it might have changed the grip of the
tires.

I get my RX8 back today, $1800 bucks and a week in the shop.

The tires will be reset to 32 before I drive away.

Just wondering where you run your tires.
Old 11-01-2010, 03:05 PM
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Ouch!
Mine acts evil on some flat wet corners especially in the cold or if it's been dry for a while before the rain.
I'd have a chat with them and see if they pulled that pressure recommendation out of the rectal database.
You may want to have your rear alignment checked out. just to be sure.
Old 11-01-2010, 03:11 PM
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I run them at the factory prescribed 32 psi.

But remember, to do that you may want to actually inflate them to 34 or 35. Why? Temperatures drop at night. For every 10º drop in temperature, your tires lose about a pound. So if you check them at lunch time and it's, say 50º — and it will be 20º late at night, you'll want to inflate them to 35. Then, even when the temperature drops at night, they'll be properly inflated. (It's better to have a little too much than too little.)
Old 11-01-2010, 03:12 PM
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The 4 lb increase in tire pressures should not have caused the spinout.
The OEM tires are summer tires, however. And if this happened on one of our recently cold mornings I can understand why it happened. It happened to me, one spring, when I put the tires on too early. Fortunately, I didn't hit anything.
Old 11-01-2010, 07:25 PM
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32 psi.

Overinflating radial tires tends to reduce grip. Opposite from bias ply tires, where overinflation stiffens the tire and gives firmer handling.

Ken
Old 11-01-2010, 07:42 PM
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I doubt the 4lbs made that much of a difference. I say performance tires with 30k are to blame. I only have 2k on mine and they are horrible when the road is wet. The first time I drove the car in the rain I thought I was gonna die...not really but I was damn near getting sideways in every turn, and I don't drive hard in the rain at all.
Old 11-02-2010, 08:29 AM
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Resu Deretsiger
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I got my EI8HT back last night. They did a excellent job. I only skinned up the right front
bumper but it did need replacing along with the brace underneath that had bent in a bit.
The first thing I did was lower the tires back to 32 before I even left the shop.
This weekend I will be shopping for new tires and will need to research that before I buy.
Only 30K on the OEM tires but I'm told that they suck even when new.
I don't drive it in the snow as a rule but I did buy snow tires and wheels last fall for
just in case. I did have it out a few times in the snow and it handled great.
Thanks for all your input.

I love my EI8HT!
Old 11-02-2010, 08:33 AM
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Resu Deretsiger
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PS, while the front bumper was off, being replaced. I did add screens over the oil coolers.
Looks great.
Old 11-02-2010, 09:25 AM
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when your cars been driven its likely to have higher pressure. the correct way is to measure it in the morning when the tires are cold.
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