Quick question regarding the correct PSI for vehicle tires. The plate by the drivers door says 30 front and 33 rear psi but the tire says 51 max psi. Which is correct? I normally go by the plate next to the drivers door.

Use the plate by the driver's door.

I go by the data plate.

Plate, as its calibrated for your vehicle's weight distribution, and correct pressures will keep them wearing evenly.

The max tire pressure on the tire sidewall has more to do with how much pressure that particular tire is structurally designed to hold safely, not what you should inflate it to drive on.

The plate gives the manufacturers recommendation considering handling, tire wear, load, ride quality, etc.

The tire sidewall number is the pressure to get the maximum load capacity rating.
The ride will be a bit harsher and the wear may be less than optimal but fuel mileage will be a fraction better due to less rolling resistance.

Many people have an opinion or preference. Mine is to run them closer towards the max on the sidewall and be sure to rotate them when I can see any uneven wear. The fronts wear more on the edges and the rear will wear more in the center with higher pressures.

What should you do? Ask 20 people and you'll probably get 20 opinions but anywhere between the plate and the sidewall will probably be fine. The worst thing you can do is run them low and unevenly.

Thanks everyone, I normally go by the plate by the drivers door.

I run my Tacoma higher than what's on the door. Door says 35, I run at 38. I've done the chalk test and with my load, 38 gives the cleanest line side to side. Plus a bit higher should help a tinny bit with MPG.

There's room to play with the pressures on your door jamb sticker, but 51 psi is going to put needless stress on everything.

There's a lot of misconception on the whole max tire pressure issue. Even pros, who should know better, still confuse "maximum" with "recommended". Here's what Tom & Ray have to say...

Question - I was recently told by my local tire store manager, while fixing a leaky valve stem, that I should be inflating my tires to the pressure listed on the tire, not the pressure listed on the door or owner's manual. In the case of my Taurus, he inflated them to 41 psi. This seems excessive. What is the answer - the pressure on the tire or the pressure recommended by the manufacturer? - Jon

RAY: The tire store manager told you that? The manager? Holy crowbar! There's a guy with his headlight firmly implanted in his taillight socket!

TOM: The pressure printed on the sidewall of the tire is the maximum tire pressure. It's printed there as a warning, meaning "if you put more than this amount of air in this tire, it could blow up." It doesn't mean you're supposed to put that much air in there. What a knucklehead!

RAY: It's like the maximum speed of your car. Your owner's manual may tell you that your car has an absolute top speed of 120 mph. That doesn't mean the manufacturer is recommending that you actually drive it 120 mph.

TOM: The pressure printed in the owner's manual, on the driver's door pillar, or the glove box door is the recommended tire pressure. That's the pressure at which the car handles, rides, steers and brakes best. And unless you've changed tire sizes, that's the pressure you should always use. And for most cars, that pressure is between 28 and 35 psi.

RAY: Under no circumstances should you inflate your tires to maximum pressure. Not only will you risk a blowout, but you'll diminish your ability to control the car because your handling and braking will be much, much worse.

TOM: Not to mention the ride! How many scabs do you have on your head from bouncing up and hitting the ceiling since this guy overfilled your tires, Jon?

Click & Clack

Discount Tire inflates the tires on my 4Runner to what's on the door plus 3 PSI.

You do have to scrutinize a little when it comes to SUVs. My '93 4Runner was sold at a time when vehicle rollovers, especially SUVs, was a real hot button. So some manufacturers addressed the issue by decreasing the pressure recommendations.

The door sticker for my vehicle says 26/35 ft/rr. The manual, on the other hand, specifies 26/29. I actually run the vehicle at 32/32, which is usually what the tire store recommends as well.

Use the plate by the door and, to fine tune your pressures, use the “chalk test”.

Here’s one explanation. There are many more.

https://fourwheeltrends.com/wh...t-for-tire-pressure/

quote:

Originally posted by NavyGuy:
I run my Tacoma higher than what's on the door. Door says 35, I run at 38. I've done the chalk test and with my load, 38 gives the cleanest line side to side. Plus a bit higher should help a tinny bit with MPG.

^^^This. Start with the sill plate pressures. Then check the tires for wear every few thousand miles. To get best wear you should be rotating them every 5k miles anyway. If the center of the tires are wearing irregularly, drop the pressure 2-3 psi. If the tires are wearing on the outer edges, add 2-3 psi. It's truly not an exact science, and every vehicle is different.

I did this wrong for many yrs. I'll admit it.
When my brother asked me to haul a trailer, that's when I should have checked for max. PSI.
I was fine but I'm sure that load brought my tires way above the recommendation.

I usually go maybe 2lbs over the door sticker unless I am towing heavy.

Tire shops like to set most everything at 35 lbs.

Chalk test. It’s the best test I have used, for tires on a fast sports car to my offroad Jeep.

Buy sidewalk chalk. Park car with tires at operating temps. Scrub a line of chalk about three inches wide across each each tire. Drive forward slowly, without turning. Pull far enough forward to see the chalk on the tires.

If the tires edges are chalked, pressure is too high. If the center is chalked, pressure is too low.

It takes some time to get the pressures dialed in, but it is a very effective way to make certain you have the largest contact patch if the tread on the pavement. I have done this on every car I have owned for more than 15 years.

This video (Jeep tires are a lot easier to see) demonstrates it very well.

Also...the plate by the door lists the manufacture's recommended inflation pressure when the tires are COLD...like first thing in the morning and the car has not been driven yet.

Normal driving will heat up the tires and the air inside them causing the PSI to rise 2 to 3 psi.
M

For truck owners, is it recommended to add some additional pressure if you're loading up the bed?

Pressures indicated on the door plate is for normal daytime temperature, and unladen.

You will have to compensate for temperature if the air is cold (like wintertime) or if the air is hot, or if the tire is warm from rolling.

Heavier loads require more pressure to maintain the proper amount of deflection as the tire rolls. If the tire is under inflated for the load, the tire will deflect too much at each revolution which creates excess heat. The excess heat can cause the tire to delaminate and blow out while driving.