I bought a nice air pump from Lowes for about 100 bucks that doesn't take up much room in my trunk, plugs into my cars accessory outlet, weighs only a few pounds and does a great job filling my tire with air in just a few minutes. No more looking for a pump at gas stations, no more enduring nonsense from tire stores and I know the pressure in each tire is at the correct PSI.

I change mine based on tire wear and type of driving. I generally stay close to recommended unless predominately driving highway/higher speeds, then I go down a couple of pounds at least. If I don't, the center tread will get more wear.

The doorplate recommended PSI isn't gospel, by any means.

Let's travel back to 2000 when tires on Explorers were separating leading to lots of deaths and plenty of accidents, and it wasn't just to the Explorer but included other Ford products.

I'll save you the trouble of Googling and just tell you that Ford recommended 26/26 PSI for the Explorer and the F150. Why? because those vehicles rode rough and less PSI made it smoother.

Problems arose when loads were in the vehicle and the tires heated up, causing tread separation. Firestone recommended 35 psi but Ford went with 26. They later changed it to 30 but millions were paid in settlements.

That doorplate number is advisory only and not gospel. I'd trust the tire manufacturer more than the car maker since the car maker's goals may not be the same as yours, as the Ford episode shows.

I'll over inflate one that I know leaks.

Maybe since yours were low...

quote:

The doorplate recommended PSI isn't gospel, by any means.

That's for sure. The doorplate on my 1993 4Runner has ridiculously low pressure specs. Why? Because at that time SUV rollover accidents were a big topic. Manufacturers used a quick fix of lowered PSI to offset the roll tendencies a bit. This is one of the rare times you should question factory specs.

The suv low pressure recommendations were an outlier. Now 2 decades later I would expect manufacturers strongly prioritize safety. Fuel economy will bias the pressures higher rather than lower. Varying the pressures can impact emergency performance, so staying close to oem recommendations is logical.

Tire manufacturers don't usually provide numbers for specific vehicles. The weight and center of gravity are important factors.

 
I have always used the "chalk test" to find the ideal pressure. Take a piece of regular black board chalk, and on cold tires mark lines across the tread (several lines). Drive slowly for about 100 yards, stop and examine the chalk lines. If they are worn off in the middle only, too much pressure. If they are worn on the outside, too little pressure. Adjust and repeat until you end up with a nice chalk line across the entire tread.
 
I have always found that the ideal pressure is 2-4 lbs higher than the door plate's recommended pressure, and my thought on that was that the manufacturer wanted you to experience a softer ride.

I run my heavier than normal e rated truck off road tires at 38 and after a few miles in the dry warm streets they come up to about 42 usually. Just clicked 40k on them and they are BFG KO2.

quote:

Originally posted by henryaz:
 
I have always used the "chalk test" to find the ideal pressure. Take a piece of regular black board chalk, and on cold tires mark lines across the tread (several lines). Drive slowly for about 100 yards, stop and examine the chalk lines. If they are worn off in the middle only, too much pressure. If they are worn on the outside, too little pressure. Adjust and repeat until you end up with a nice chalk line across the entire tread.
 
I have always found that the ideal pressure is 2-4 lbs higher than the door plate's recommended pressure, and my thought on that was that the manufacturer wanted you to experience a softer ride.

Our tires have 2-4 pounds extra pressure once they’ve heated up. If you do the chalk test on cold tires and find they need 2-4 pounds would that mean they’d be about right hot if you didn’t add any air?

I’ve been using door plate pressure on most of our vehicles and my tires wear evenly across the tread.

My Tundra has a stupidly low pressure recommendation. Gotta have that cushy ride don’tchaknow.
The truck wallows terribly when tire pressure is set there.
Aftermarket tires have a max pressure of 50 psi. That’s where they stay.
I have a heavy as hell tonneau cover and the gas mileage at door panel recommendations is REALLY bad compared to the bad mileage I normally get.

Seems if one gets an oil change or tires worked in, you have to check later when home.

The oil change place may short you 1/2 a quart, the tire place can mess up your psi.

You can measure your tread depth across each groove, record it on paper, take the average for each tire, and note any tire that has tread depth greater or lesser in the middle then on the outside, and so adjust your pressure based on those results. This is a general approach, because there are too many variables to answer the question for all situations, but if your tread depth wears evenly across the width of the tread, then you have more or less ideal contact patch and maximum traction, so to speak, other things being equal - ie, are you driving to work, are you racing to work, are you actually racing on a track, are you hauling heavy loads, are you driving in sand on the beach, the list could go on. I do this little measuring of tread depth analysis on all my vehicles, which guide me on choosing tire pressures. For example, if your car is much heavier in the front than in the back, for example driving an empty f150 around all the time, the pressure on the placard might cause your center tread on the rear wear faster than your outer band treads, meaning you may want to lower the pressure a little bit lower than what's on the placard, just as an example. BUT, that my not happen with another brand and rating of tires, it's a matter of understanding the purpose and tradeoffs for the type of driving and your particular vehicle.
there's no valid general recommendation to answer the original question. None, nada.

I wouldn't inflate tires to way more than the door sticker. The manufacturers come up with that number for even tire wear, mpg's, ride, and braking. I usually prefer to run 2 psi higher and then add air when it gets to the door sticker number.

quote:

Originally posted by henryaz:
 
I have always used the "chalk test" to find the ideal pressure. Take a piece of regular black board chalk, and on cold tires mark lines across the tread (several lines). Drive slowly for about 100 yards, stop and examine the chalk lines. If they are worn off in the middle only, too much pressure. If they are worn on the outside, too little pressure. Adjust and repeat until you end up with a nice chalk line across the entire tread.
 
I have always found that the ideal pressure is 2-4 lbs higher than the door plate's recommended pressure, and my thought on that was that the manufacturer wanted you to experience a softer ride.

This right here. I was about to post the exact same instructions. This is by far the best way to do it. It takes into account the whole contact patch and the weight on that tire.

My Jeep Wrangler door sill placard said 37 psi. An Abram’s tank has a smoother ride than a Wrangler at 37. I usually ran around 30 psi as that’s where the chalk method showed the best contact patch.

In all of the cars and trucks I've owned, I've never been able to tell a difference in ride quality due to tire pressure. The tires have temporarily been 10psi or more under, and sometimes even up to the max psi. It's always felt pretty much the same. Steering feel does change though. Maybe I'm just not sensitive enough.

quote:

What's the purpose of inflating tires to way more that factory specified pressure?

It keeps the tire dude from having to contend with the inconvenience of looking at a tire pressure gauge.