My tires recommend 30psi. This time of year I can have anywhere between -16F and 32F. What cold pressure should I have to insure that I will still have sufficient pressure in the below 0 temps to avoid flats?
Tire pressure is checked cold so whatever temp it is out, that’s the temp you put the pressure at 30 psi at. When the car starts rolling, the tires heat up, and pressure builds again. So the the cold psi is the lowest it should be at the outside temp. Cold air is denser so the colder it gets the lower the pressure will be which is why you have to add more air in the winter and why so many cars run around with low tires in the winter.
Rule of thumb: For every 10?F change in temperature, the pressure will change in the same direction 1 psi.
You posted a 48?F spread - that would be about 5 psi.
Just keep it at the pressure recommended in the car’s owner’s manual. When the temperature gets cold the tyre pressure will go done and you may need to add some are. Don’t let air out because it shows higher pressure after you have driven the car. Don’t use the pressure on the sidewall of the tyre as the correct pressure for your car.
Are you giving the range of early-morning temperatures or the range of temperatures throughout the day? You want to set the tires on one of your colder mornings. If the pressure is a little higher on a warmer day, that’s better than the other way around.
One of the many reasons why I inflate my tires to 3 or 4 lbs over the car manufacturer’s recommended pressure is because I don’t want underinflated tires on an extremely cold day.
On a day that is in the mid-range of the temperatures that you noted, inflate the tires to 3 or 4 lbs over GM’s recommended pressures and you will be good to go, no matter what the temperature.
I recommend checking your tire pressure every few weeks, and of course, you need to re-evaluate your tire pressure at every change of seasons.
Also, in extreme cold, tires will lose air pressure quicker than in summer…They become more porous…
Thanks for the advice. Maybe this will keep me from getting a flat like last year. -16 with 45mph winds is no fun to chang a tire.
Ok, so the thing I’ve never quite understood about this advice (that the door rating is what you fill to regardless of the outside temperature, when your tires are cold) is this:
Doesn’t the air in the tires eventually heat up to the same temperature during a long drive regardless of the outside temperature? ie, my tires are very warm even after a long drive in winter, just as in summer.
If that’s correct, then filling to 30psi at 10?F, then heating the air in the tires while driving to (say) 100?F will cause higher eventual pressure than if I’d filled to 30pst at 70?F then driving and heating them to 100?F, right?
I suppose the answer is that the outside temperature affects the temperature of the air in the tires, even after hours of freeway driving. Either that or the ‘extra’ inflation one gets after driving is only 1 or 2psi, and therefore it is better to be slightly over-filled after a long drive than underfilled when cold.
Can anyone see what I’m getting at?
I don’t think your tires will heat up to the same temperature. I’d bet they’d be much hotter after a drive on a 90F day than after the same drive on a 20F day.
I dont have to deal with temps below about 7 degrees, but I underinflate about 3 lbs in winter to give more tire on the snow/road (usually less the 3 inches here) and overinflate about 3 lbs in summer to give better gas milage due to less friction. I also underinflate when driving on sandy roads, and carry a battery operated pump and tire gauge to re pressure when transiting to hard pavement. only takes a few minutes, plan ahead.
Tires will be hotter at the end of a drive on a hotter day than on a cooler day. They will be hotter on a sunny day than on an overcast day of the same temp. They will be hotter on the sunny side of the car than on the shaded side. They will be cooler when running on wet pavement compared to dry at the same ambient temp.
My point is? You can’t worry about all those variables if you have a life. They are not that significant. If your life is race car driver, or crew chief, you will because they are significant in that case. For the OP, just set the temp for the cooler day. It is better to be a couple of pounds over than under. Use the 10 degree/q psi if you don’t want to be out there on the coldest days.
I just inflate to 1 or 2 pounds over in the fall/early winter and I don’t in the spring/early summer.
add a bent jack and you know what I went through ~5 years ago. Tire was so cold and hard, it flopped right off the wheel. Went to jack it up and the already-bad factory scissor jack was bent, so I had to wedge it and use all my weight and both hands to turn it until it partly straightened itself.
lol @ “You can’t worry about all those variables if you have a life.” I think you are definitely right 
I won’t worry about it. Just did my tires and found the spare was at 20psi, so that was definitely worthwhile.
Thanks all,
James