Proper tire pressure?

[Nova Kaw 650]

Does anyone remember the issues with firestone & ford ?

Ford put a low number on the door for comfort, and the tires failed or caused rollovers because they were not inflated properly.

The same thing can happen if you do not replace your tires with the same size, brand, and load rating.


And on vehicle tires, the rating on the side is for the MAX load, not normal. They use to have max & min inflation pressures on them, but the minimum was removed many many years ago.

Running at max without the load to support running that pressure will only wear them out faster in the middle, let them spin/slip easier, and and beat you up riding around.


If you replace your tires, you must use due diligence to determine what air pressure is needed for proper handling, comfort, and safety. Blindly using the number on the door jamb may not the best idea.

The number on the door is based on the characteristics of the tire that was on it when you bought it. Change the tire, then it is highly likely the characteristics will also change.


If you have an E rated tire, and you only run the 32 or 35 psi that is on the door cuz the manufacturer expects a P, C or D rated tire to be on the truck, chances are it will wallow on turns and give you slow/sloppy handling. This will also increase flex in the sidewall and prematurely weaken them which could lead to a blowout or other problem.

Read post #17 ^^^

[TRCM]

Read post #17 ^^^

ha ha...you posted while I was typing......

[haveme1]

Stock tires on the door. My 4x4 rides too rough so I go 2lbs lower.
Boat trailer exactly what the tire says No matter what.

[Nova Kaw 650]

ha ha...you posted while I was typing......

[mysuzytoo]

I've always done the door!

[Marshfly]

Not a single one of these responses referencing anything but use the pressure on the door jamb for stock size tires only is correct.

Tire manufacturers publish load charts that specify what pressure to run for a specific tire size to carry a specific weight. That guide also gives you the math to use to convert your stock tire pressure to the new pressure. Guessing, how it rides, and chalk tests tell you nothing.

Here is Toyo's guide. Since the load charts are actually published by the Tire and Rim Association, they will be consistent for same size and load index tires from different manufacturers. If you aren't using an actual load table to find the proper inflation pressure, you're guessing.

https://www.toyotires.com/tires-101/...flation-tables

[grandbassslayer]

Marshfly is right. I've never looked in the door, I follow the tire manufacturers guidelines.

[Skeet'r89]

I do something like the chalk test but even less high tech. I look at the tire and see if the road scuff is running over the edge of the tread. If so I add air. If the road scuff is not out to the edge of the tread I reduce some pressure. Right or wrong???? That's what I have done for years and usually get pretty good tread life on my vehicles.

[haftafish22]

I do something like the chalk test but even less high tech. I look at the tire and see if the road scuff is running over the edge of the tread. If so I add air. If the road scuff is not out to the edge of the tread I reduce some pressure. Right or wrong???? That's what I have done for years and usually get pretty good tread life on my vehicles.

Thats a a good idea but tires change shape drastically with increase in road speed.

[TRCM]

Thats a a good idea but tires change shape drastically with increase in road speed.

On a dragster yes, on a street car, not enough to matter unless you are spinning high rpm with soft sidewalls.

[Marshfly]

I just don't get it. I can figure it out with 100% accuracy using the data in the link I posted above without leaving my chair in significantly less time than it takes to do any kind of "test."

Seriously, any method other than using the load and inflation charts is guessing.

[Corkpuller]

My pickup I typically run 10% less than MAX rating on the tire.

I remember years ago when my Grandpa had bought a new car for Grandma and it was the first time he'd ever owned a Radial tire.
He was always worried about them tires because they looked FLAT.

[Jdub176]

I do not use what is on the door, because that is for ride comfort. Case in hand when I run what is on the door of either my wife's car or my truck the outside edges of the tires will round over. For me I look at the tires. If the outside edges see more wear I will add a couple of pounds. If middle of the tire is wear more I will decrease the pressure a pound. My f150 says 35 lbs in all tires. That is way to low and I get accessive tire wear on the edges of the tires. I found running 37-38 lbs per tire really balances the tires wear out. The truck rides a little rougher, but I get better milage out of the tire. Interesting fact on my wifes car I have to run 33 lbs of pressure in the left side tires and 34 lbs of pressure in the right side, so the car will drive strait down the highway. Also doing this the tire will wear more evenly. I don't understand it, but after 110,000 I do what works best.

[Idaho Sandman]

Ram 1500 4x4. 38 in the fronts and 35 in the rear tires. Tire wear is perfect. If I’m going to tow the boat or load up the bed with weight for a long period of time, I will inflate the rear tires to 40.

[TRCM]

I just don't get it. I can figure it out with 100% accuracy using the data in the link I posted above without leaving my chair in significantly less time than it takes to do any kind of "test."

Seriously, any method other than using the load and inflation charts is guessing.

Those charts are averages....the chalk test is not an ave, it is the way things need to be for your vehicle. Do you know the 4 corner weights of your truck ??

I can sit here and figure out a lot of things on the computer, and try to use them, and find out the 'numbers' aren't exactly right and it just doesn't work.

The chart you mention doesn't take into account any aftermarket items you may or may not have added, nor any other stuff that changes weight/load, nor the variables in different rims, or even tire construction which is part of the manufacturing process.

It should get you close tho..................

[grandbassslayer]

Those charts are averages....the chalk test is not an ave, it is the way things need to be for your vehicle. Do you know the 4 corner weights of your truck ??

I can sit here and figure out a lot of things on the computer, and try to use them, and find out the 'numbers' aren't exactly right and it just doesn't work.

The chart you mention doesn't take into account any aftermarket items you may or may not have added, nor any other stuff that changes weight/load, nor the variables in different rims, or even tire construction which is part of the manufacturing process.

Those charts were done by engineers to ensure the tires get you home safely. They test them at payload and pressures to determine what will and will not work. I run some 35" toyos, but I run them at less than max PSI for comfort. I also pull a heavy load, and for it to be safe I had to consult the Toyo charts so I don't kill myself or someone on the road. I don't think a chalk test can do much beside get you close for even wear.

[TRCM]

Those charts were done by engineers to ensure the tires get you home safely. They test them at payload and pressures to determine what will and will not work. I run some 35" toyos, but I run them at less than max PSI for comfort. I also pull a heavy load, and for it to be safe I had to consult the Toyo charts so I don't kill myself or someone on the road. I don't think a chalk test can do much beside get you close for even wear.

Chalk test IS for even wear you are correct.....if you are loaded to max, you have to go with max pressure OR do the chalk test again loaded.

Believe it or not, if you have the max pressure in your tire that gives even wear, you are at the pressure you need to be for the weight the tire is carrying, unless you have some very strange rim/tire combination.

When you add load/weight, you need to bump the pressure up to support it.

If you have a truck, and you have added a front winch bumper, a fancy rear bumper, bigger tires/rims, a bed toolbox, and nerf bars/sliders, and who knows what else, you no longer fit the 'stock' truck profile that was used in those charts.

You now have to know the actual corner weights or at least the actual axle weights of your truck to properly use those charts. That's what I am trying to get across...most people who need to adjust the tire pressures to account for mods they've made don't know the trucks actual weight to be able to correctly adjust them.

[txsunfish]

This thread is about vehicles but on a trailer tire should you max the pressure out or base the inflation pressure on the combined weight of boat, motor, and trailer combined? Sorry to hijack the thread. Thx.

[TRCM]

This thread is about vehicles but on a trailer tire should you max the pressure out or base the inflation pressure on the combined weight of boat, motor, and trailer combined? Sorry to hijack the thread. Thx.

Yes, trailer tires should be at max pressure per the sidewall, but you should also make sure you have the appropriate size & load rating tire installed.

It should be based on the weight of the boat, motor, trailer, and any load in the boat (fuel, tackle, etc).

Generally, you can go by the trailer ratings on the load placard.

[basscat21]

Just remember in a couple months you need to change to Winter air, pretty critical in colder temps.