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I know that this topic has been discussed before with no clear definition of "high" speed or what "cold" is. I was reading the manual to my mom's '95 Del Sol and in there it mentioned pressing your tires up when traveling at high speeds. In her manual it clearly states that high speed is over 100 MPH (160 K/hr). I also was doing some surfing and found a government site that defines what "cold" tire pressure is. You can find that in the following link. It states that cold means a vehicle has not been driven for at least 3 hours. I know this doesn't take into consideration ambient temperature. So, I would assume that the tire industry would take that into consideration.

http://www.safercar.gov/staticfiles/DOT/safercar/pdf/What%27s_Your_PSI_brochure.pdf

"Cold tire pressure" is the tire pressure at ambient temperature. If a cold front comes through, you had better check them again, because the pressure will go down from the lower ambient temp. You will see a difference in pressure from tires that are in the direct sunshine compared to the other two tires that are in the shade.

I'm loosely paraphrasing Hobbit here :)....

There's a HUGE safety margin between recommended pressure (max sidewall) and blowout pressure, something like 5:1. There has to be, for any number of reasons... but here are a few.
- Say your car is outside at 20 degrees F and you have your tires inflated to max sidewall (I'll use 44 PSI for that number, may be different for your tires). It's been sitting overnight so it's definitely "cold". Now you drive someplace far away and warm (say 80 degrees F). If you checked your tire pressure right after stopping it would be well into the 50s. Yet you never inflated beyond max sidewall.
- Say you hit a particularly nasty pothole in the road with your properly inflated tires. What do you think the instantaneous pressure spikes to in the tire that hit it? Again well beyond that number.

So even though the number on the tire is listed as "MAX sidewall", road conditions and temperatures can drive pressure above that number, yet your tires do not blow out. These factors are definitely taken into account when coming up with that number you see on the tires.

Hi Jerad:

___No need to paraphrase wrt blow out pressures. That is the minimum number I have been told by more than one tire manufacturer engineer and passed onto Hobbit a while back. In some cases, the rims break before the new tire blows ;)

___Good Luck

___Wayne

In some cases, the rims break before the new tire blows ;)

I can attest to that from personal experience. :(

-soD