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Discussion Starter · #1 ·
After taking car in for service it was noted I had some wear in center of tire. Usually the tires wear rapidly inside, so I am assuming that it is probably from overinflation which I purposely did for winter storage. When the roads were dry I would take it out, but being lazy I didn't drop the pressure. Now that I know that I may have caused premature wear I have learnt lesson, I will drop them to correct pressure.

But that is the question. When it is 32 degrees F, do I take them to the standard 32 Front 29 rear lbs?

Disclaimer: Before any one gets on my case, ;) I know I should use winter tires when this cold, the P zeros suck, but for the occasional drive in dry weather, I don't think it is worth the expense if I drive carefully around corners, accelerating etc. I go into withdrawal; gotta hear the roar of the mighty V8, X center pipe, and Larini rear boxes! :D

Or should I put a bit air more in? Is there a formula to compensate for temp / volume / pressure that is useful? It has been a long time since high school physics!
 

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Cold tire pressure is just that - the air pressure when the tire is cold (i.e. no driving for many hours/over night), and you should check/adjust as the temps change. I check ours monthly, but we are in northern California - temp doesn't change to rapidly. If your clime is one where one week will be 70° and the next will be 30°, you should probably adjust the pressure more frequently...
 

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cold tire pressure is just cold tire pressure.

if you are driving your QP around, you should be able to monitor the actual tire pressure changes as they warm up. that would be an important number to look at as well.
 

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Discussion Starter · #6 ·
For "clarity

Just wanted to be clear that I understand what cold tire pressure is, i.e. measured before driving. My question was really, is there a range of ambient temperature in which the cold tire pressure is valid. If it is extremely cold or hot outside, do you still inflate to to the specified "cold tire pressure" or do you add / subtract some pressure because the temperature is outside the extreme range.
 

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In the winter, I increase tire pressure 5 lbs and put the car on 1" rubber mats--all to avoid flat spots. If I drive it in the winter, I go back to spec pressure and reinflate when I put the car in the heated garage. I got 7,000 miles on a set of P Zero Rosso's with moderate driving--I'm trying Toyo's with slightly harder compound (280)--Got 10,000 miles on Michelin PS-2's on 2002 Coupe.
RWS
 

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Just wanted to be clear that I understand what cold tire pressure is, i.e. measured before driving. My question was really, is there a range of ambient temperature in which the cold tire pressure is valid. If it is extremely cold or hot outside, do you still inflate to to the specified "cold tire pressure" or do you add / subtract some pressure because the temperature is outside the extreme range.
The pressure change vs. temp is given by P*V= n*R*T, so you can see that for n, V, and R held constant, P & T are directly proportional. If one increases, so does the other. Your last sentence touches on what I was trying to explain. In this case, "cold" means whatever the prevailing temperature is. If you set your cold tire pressure to 32 psi in 32°F weather and the temp drops to 10°F, you would have to add more air to get back to 32 psi. Just the opposite if the temperature goes up. Hope this helps...
 

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The pressure change vs. temp is given by P*V= n*R*T, so you can see that for n, V, and R held constant, P & T are directly proportional. If one increases, so does the other.
To put rough round numbers on it, at 20C / 70F ambient, and 30 psi / 2bar in the tires, every temp change of 5 degrees C / 10 degrees F results in about a 0.5psi / 0.03 bar change in tire pressure.

So if you want to keep your cold tire pressure within 1psi / 0.07 bar of a particular value, you would want to readjust it for every 10C / 20F variation in outdoor temperature.
 
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