My turbocharged PT cruiser has low-profile, high performance tires (recently replaced with same size tire as when new). The tire indicates a max pressure under load of 50psi. The label on the driver door states to inflate to 38 psi. When I look at the tires at 38psi, they look a little low. I’m concerned that the tires may wear out faster and not give as good mileage compared to inflation at a higher psi. Which inflation number do I use? right now I’m splitting the difference.
Thanks in advance!
The door placard is the correct tire pressure for the vehicle. The MAX pressure you see on the tire is what the tire manufacturer recommends for that tire because that tire can be used on many different vehicles. How a tire looks when it’s inflated to the proper pressure shouldn’t be used as determination if the pressure is too low. You have to remember, as you drive down the road the air in the tire is going to heat up. And this will increase the tire pressure.
Tester
You should always inflate your tires based on the placard on the driver’s side door. You should always check and inflate them when they haven’t been driven for several hours. Also, make sure you’re using a good and accurate pressure gauge. The public ones at gas stations are usually inaccurate.
“Maximum” and “recommended” are not synonyms.
Door label
Door label. Those tires will fit more than one make/model of car. So it makes sense given different cars have different weights/camber/caster/suspension geometery/etc. that they would call for different air presures. Now you can adjust tire pressures for different types of driving. When I bolt my drag radials to my car. I only run about 20 psi in them so that the contact patch is a little bigger and thus provides better grip. When I take my Bronco out on the beach, I’ll air down to 15 psi or so, again to maximize grip in the sand. However driving on public streets with air pressures that low would be a problem because with air pressures that low steering is dangerous and the tire could come off the bead.
“high performance tires (recently replaced with same size tire as when new)”
Door.
If you had said something like - and I replaced the wheels with a plus size and lower profile tires - then I would say no more than the maximum. At that point you have to just see what works for the best traction / wear you are after since the door card no longer applies.
Definitely door. As others have said looks are not how you determine pressure. Also, the tires will increase in pressure as the tires heat up. If you want to get scientific about it though you can get a high accuracy surface temperature gauge, drive the car hard, and then measure the tire tread shoulder and the inside of the tire tread for temperature. The tire should be fairly uniform in temperature across.
However, I know you’re not going to do all that so use what’s on the door. Besides, if you jack the pressure up you subject the rim to more possible damage over harsh surfaces. Get a quality dial gauge in case yours is defective as well.
Door label. This fair and reasonable question comes up repeatedly and should be addressed by vehicle and tire mfrs. presently asleep at the switch. Possibly they need or desire some government intervention. A simple statement added to the door label would suffice: Tire sidewall pressure is for tire installation on rim only. An addition to the sidewall would state: Use vehicle mfr. recommended pressure.