O/T-Can I ask about car tires/pressures

Tires on car say load limit 1653 pounds @ 35 PSI. Looking at new tires. They say 1653 pounds at 44 PSI. Same brand of tires. Look identical. What do I do about pressure???

I would run the tires as they are marked - maybe they changed the composition of the tire or something.

The new tires have a heavier ply rating. They will give the best gas mileage at the maximum rated pressure, but might be a little harsh over road cracks. There are pressure ratings on your door post, but not great for gas mileage.

Gerald J.

Currently, the door post recommendation is to run the rear tires at 35 PSI (100%) and to run the front tires at 32 PSI (94.1%). I thought about following these percentages on the new tires. Might be a little rough over the bumps. Thanks for your response.

I think you will find those values are the maximum ratings. Optimum pressure is that which keeps the full tread just flat on the surface. Too little pressure, tread will wear on outer edges and carcase will flex and heat sidewalls; too much, and braking may be impaired due to less footprint and tyres will wear in the middle of the tread pattern. Yes, better fuel economy at higher pressures, but that is not the only thing all that tyre development cost was about. One is yours and others safety.

Regards, RAB

Tire pressure is determined by a lot of things Weight tire size are the most important parts. On the door or under the hood you will find the proper setting if stock no load. If you have extra load then go up a couple of lbs to see how it handles. If you have over size tires then drop a few lbs.

The two most important things are tire wear and handling If you get wear in the middle go down on the outside go up. Over steer go down under steer go up. The vehicle should drive with little help from you as goes down a straight road.

Walt

If you read on the tire it says MAX tire presure. This is for the tire only. Not the vehicle it is on.

They test each model car and determine the tire size and what pressure should be run. If you're using the recommended tire it says for your car then run the recommended pressure.

If you get some butcher paper from your local meat store and lay it on a smooth concrete floor of a garage and drive over it slowly it will show you the pattern of your tire contact to the road.

If the pattern or imprint from the tire to the paper is consistent all the way across the width of the tire then you're good. If it shows contact on the paper only in the middle of the tire tread
you have to much air pressure in the tire. If it shows only the outside edges of the tire to be touching on the paper you have too little air pressure in the tire.

If you haul heavy things you will want to put a little extra pressure in the tires, running an overlaoded tire is like running a low or flat tire.

There is wire in the sidewalls of tires. And you know what happens if you bend a wire a lot of times fast, it heats up and will eventually break. Well this is what happens to tires. The side walls become hot and weak then split open. They call this a zipper crack. That's why you have to be careful airing up a tire that has been run flat. It can kill you if it would explode and for that to happen it only takes no more than 20lbs of pressure in the tire.

I don't know if you ever seen or heard a tire explode, but I have and felt the results of it. When you come to you will wonder what body part you are missing if you can feel pain. I've seen some really bad cases in the "Head Trauma Center" in St. Louis Hospital, you wonder how some of these people lived after being hit by an exploding tire.

For the best handling and safety of your car, follow the tire pressure ratings on the door sticker.

To up the gas mileage just a bit, run an extra 5 psi in them. I only use the max pressure rating when I'm going fully loaded for an extended trip.

Pappy, your new tires have a higher load index (though not necessarily ply rating) and are capable of holding more air pressure and this more weight. Load index is the 2 digit number next to the speed rating ( ex: 94H).
The correct way to determine inflation for these new tires would be to go to the load index chart in the "Tire Guide" (every tire store will have one), look up the old load index (ex 92) and cross reference the car maker's suggested inflation with the weight in the book- then cross reference this weight with the proper inflation for the new load index (should be higher). Simpler, just add 9 lbs- it will probably put you in the ball park.
That being said- on modern radials, you will almost NEVER see one fail due to OVER inflation- infact, you will be hard pressed to find one in a million scrap tires that even exhibit signs of over inflation. Modern tires fail or wear prematurely for these reasons- road hazards/ impacts (made more susceptable by low inflation), alignment wear (also exagerated by low inflation), and low inflation. AIR 'EM UP!

Doorpost and Operators Manual recommendations are
compromises for undocumented reasons. I believe Max inflation imprinted on the tire is a better
guide.

I have had the best results in fuel economy and tire wear using an IR temp gun to scan across the tire surface and adjust tire pressure to achieve a uniform temp across the tread after a half hour of operation. It often requires added pressures on loaded vehicles and ocassionally lowered pressures on empty vehicles.

Starting with Max pressure at the max load on the
tire sidewall and adjusting to the same proportional pressure per actual load seems to be
a good place to start rather than the pressures
for unlisted variables that are on the door post.

Being in the car business, I can see all the time from the tread wear when the tire has been run over or under inflated. Stick to the placard on the vehicle for tire pressures. If you don't, and someone blows a tire, YOU could be on the hook for a lawsuit.
Patch Rubber co just came in to our shop to talk about fixing tires and told of one of their dealers that was held liable for 30% of a $13 million lawsuit for patching a tire with a string plug. The tire blew and the driver flipped the vehicle. It put the dealer out of business.
Then there is the mandatory tire pressure monitor system the government requires on all vehicles up to 3/4 ton trucks. It's just not worth the liability or the hassle that comes from substituting your values other than what the manufacturer states.

I'll send you a tractor trailer load of 500 scrap tires and I'll bet you don't find 1 worn out due to over inflation- it's that rare. Also, TPMS only goes off on low inflation- not over inflation- kinda proof that overinflation isn't a "top of mind" concern for the liability boys at the car companies. Underinflation is such a huge compromise to handling and safety...and the door jam inflations are such a compromise to ride quality (almost always on the low side)...a real hazard, sometimes,
As far as door jams go- the Ford Explorer door jam PSI had the 235/75-15 on that application overloaded right out of the gate, so I'm hard pressed to beleive that there is much science involved in those numbers.
I'm just a tire guy, though-wadda I know? sold 742 yesterday and hope to sell 500 mre today if it keeps snowin'!

jose,
Exactly right air em up!!! That is what got Ford and Firestone in all the trouble Ford engineers recommended a low pressure so the could sell a rough riding vehicle (explorer) to the soft bottom soccer moms. All tires loose air over time and when you start with minimal inflation you are asking for problems.

Unless they start wearing the tread in the center faster than along the edges. Pump the tire to it's max rated pressure.