C rated tire psi

It doesn't matter much if they are P, D, D, or E rated. The number on the door is a good starting point. The number on the tire is for max loads. I like to run my tires a with a little more air in them than what is on the door sticker regardless of the load range. Somewhere between 32 and 40 PSI sounds about right depending on how heavy you're loaded.

 

Did you just assume her truck's door jamb label shows the same pressures as yours? The label pressures change depending on the OEM wheel and tire size for the particular model. That's why the owner's manual lists 5-6 different pressures.

Trucks with port installed tire and wheel pkgs would have a different label still. Toyota issued a recall once because they missed adding the label on some of these trucks.

 

All the pressures (owner's manual, door jamb label, the max pressure shown on the tire sidewall) are cold.

 

Always use the cold inflation pressure -- even here, nobody is over the top enough to adjust their tires while hot every trip.

The engineers have calculated the increase in pressure when they specified the number on the door post.

Sitting in the garage or earlier in the morning is a better time to check, after sitting in the sun the tire pressure changes quite a bit.

Your load range C tires should be fine at the factory pressure recommended or a few pounds higher if you prefer a firmer ride when daily driven. For daily driving you don't want to operate at a pressure lower than the factory recommended one.

3 or 4 pounds can make a noticeable change in the feeling of the ride without much impact on tire wear so it is fine to set a pressure and drive for a week to see how it feels.

When carrying a heavy load you can increase the pressure up to the 44 pound maximum to improve handling and help the tires run cooler. The full 44 pounds is probably not needed with a Tacoma due to the fairly low payload. Naturally you would add more air to the rear tires than the front. Decrease the pressure back to normal when unloaded.

As others have said you can do a chalk test if you wish, it is more important however to monitor the wear over time, refer to the photo below.
Your hand can detect unusual wear before your eye will see it, get in the habit of inspecting the tires once a month or so.

 

Do not waste your time with the chalk test. There is NOTHING scientific to it. It is merely a novelty.

Tires do not dictate your air pressure so switching to a c load range tire does not change your truck. It still weighs the same and still has the same carrying capacity.

Every change you make in PSI is a trade off. Go low you get a cushy ride, but poor mileage, lower load capacity, shortens tire life, etc. Go high you get a stiff/harsh ride, but you get better mileage, longer tire life, increased load capacity, etc...

 

32 (cold) for me both front and rear on Toyo AT III. Seems to ride a little better and no wear problems. I'm not too particular,

 

I was asking the same question here recently. I eventuality settled on 34, it seems to be the best trade off between mpg and good ride

 

on michelins defender LTX MS

 

I wouldn’t overthink it. If set it to 32 and someone snuck 2 more psi in there you would never feel it or see any different wear patterns because of it. 32 is fine 34 is fine 38 is fine. Just keep an actual tire gauge and check them ever couple of tanks of gas and your good. Test out a few different pressures and see what you like best just don’t go below factory recommendations or above about 40 or you will probably start to see some uneven wear.

 

I run 32 psi cold with my 265/75R16 Cooper Discoverer AT3 LT ("C "load).

 

34-35 psi for stock weight. More psi once you start adding bumpers, armor, winch etc.

 

Go and buy a good tire gauge too.
If you go to your local NAPA store they should have a USA made gauge made by Milton Industries, they are good ones.

 

^^

This

 

The number in the door jamb is for the tires the factory used and is based on P metric, metric, LT metric, or LT (standard). It is also based on the load rating of
the stock tire, if there are multiple options on the market for the stock size used.

I don’t know what exact tire size and load rating you have so I’ll use a TRD OR as my example. 265/70R16 (NOT P265/70R16), 30 PSI (front and rear), SL (112T) load range.

Non LT tires are fitted with a 10% overage for extra carrying capacity, so the stock TRD OR tires are basically set up in a way to carry 2121lbs @ 30 psi. With LT tires you can lose the extra 10%, so you need to carry the equivalent of 1948 lbs. when you enter into a tire pressure calculator the LT265/75R16 load range C info, it spits out that you need to run them at 36 psi.

Start with an accurate baseline on the calculator by entering your exact stock tire specs and pressure and then enter the appropriate info for your new tire and you will then know what you should run to maintain the proper manufacturer design pressure. It’s basically just figuring out the best pressure for your new tire to support the same weight as your old tire did. I would not just run what the door jamb says and I wouldn’t bother with a chalk test.

 

What is interesting about LT tires is their load capacity is designed to be used mostly proportionally across the PSI range up to a max pressure of 80. The tires I intend to use are LT235/80R17 and they will need to be inflated to 42 psi to carry the same load as my stock TRD OR tires.

Without airing them up to 42, technically they would be under inflated for the load they are supposed to be able to carry on my truck. May not matter, but I’d like to maintain the design intent, so I will run 42 when I get them. It’s just math.

 

Your tires' 'new recommended psi' is 37.

Read this if you want to know why.
https://www.toyotires.com/media/3729/application_of_load_inflation_tables_20200723.pdf