How do you determine a correct tire pressure?

Okay...
I like the idea of the chart that "splitbolt" provided over the bias ply chalk test (what, too easy?) but, I have to admit, I don't quite get it. I'm neither a car guy nor much of a math guy homer:doh!) and would need some more information.
Such as, is the 2,149 representative of an OEM tacoma (I don't have my old tires) and I use the 1,954 value? How do I use that value?
I get the tire size on the vertical axis of the chart, are those psi across the top?
What are the intersecting values, weight/tire?
I'm genuinely interested, can you spoon feed me how to use this?

 

My point... you can have up to a four psi at any given time

Lol man. Just put 32 psi in it and call it a day. I run 35 psi because I tow a lot. 32-35 psi is good to go. Your TPMS goes off at 28 psi. Better mpg can be had with a bit more pressure.
However! Set your tire pressure at night after truck has sat for a bit. This way, all tires will be the same and you have a good start point.
Seriously, tire pressures vary up to 3-4 psi without you doing anything.

 

Try the calculator I linked. (Post 19) It accomplishes the same result without any work. This and the chart are based on GAWR and tire size/load ratings. SL and LT tires require different pressure for the same load. And, different sizes require different pressure for more obvious reasons.

You can adjust the pressure to your liking, but these are a good starting point.

 

I put numbers in, but are they correct for OEMs? Looks like 36psi? Thoughts?

 

3d gen Tacomas have a inflated load weight of 2,149 lbs-2,172 lbs from P and euro metric tires.

Examples:
265/70/16/112 @ 30 psi = 2,149 lbs(Offroad)
P265/65/17/110 @ 29 psi = 2,149 lbs(Sport)
P245/75/16/109 @ 32 psi = 2,172 lbs(SR)

The vehicle manufacturer de-rates euro-metric and P-metric tires for use on trucks and SUVs.
If you switch to LT tires, the new inflated load weight is 2,149/1.1=1,954 lbs.
Use the LT load charts to find the PSI that attains this weight for your particular size.
What I did was extrapolate a value for 1 psi based on the weights between 35 and 40 psi to arrive at the 31 psi recommendation. I will concede, LT tires are supposed to have a minimum inflation of 35 psi, but I feel comfortable calculating it down to 30.

This Toyo pdf explains it more in depth and has all the charts.
https://www.google.com/url?sa=t&sou...FjAAegQIBBAC&usg=AOvVaw1v0RyQdiINxLjc4FG6ti4v

 

OEM should be 265/70/16/112

 

@splitbolt definitely understands this stuff better than me. That's why I use the calculator.

But, you must start with the OEM tire size and pressure specified in your door jamb. I don't believe 265/75/16 was a stock tire size. I could be wrong, though.

 

Okay, it came out to 35 instead of 36. So, there i have it...

Set a base "cold" psi around 35 and it will vary anyway and, more importantly, generally be fine. They are set so high now they are obviously crowned.
Did not even bother to see where they are at until I knew where to go.
I have no business working on my own truck! I just like driving them. Life is hard, it's harder when you're stupid!
Great help from everyone, thanks!

 

Drive it at different pressures and see what you prefer. OEM tests generally are to optimize mpg. Manufacturers (of tires) generally are to optimize safety. Personal preference usually is different. Try 34 psi and drive around. Go up and down to taste. Many will suggest the chalk test. It helps but is kind of the BMI of tires, better than nothing-does work when standard deviation is zero-is simple. It’s a vehicle, how does it drive.

 

I just noticed your sig says you have a camper, you do realize you'll need to up the tire pressure considerably when you haul it.

 

Hi. Usually using sticker on B-Pillar(driver side.) Changing from R17 to R16 sticker number will apply, IMO.

 

It won't be necessary if he uses the pressure determined by the calculator or by the charts @splitbolt provided. That pressure will be based on GAWR, so it should be fine unless the vehicle is overloaded.

 

Sorry, but how would it not still be a useful test with radials? Obviously chalk test results would change while towing or carrying heavy loads but it would still show your tires (bias-ply or radial) contact patch width no matter what load rating tire you run.
The only thing I would do differently in that video is to get the tires up to normal operating temp before the test.

 

The contact patch on the radial tires doesn't change nearly as much with air pressure as a bias ply would, so the range at which you get a good contact patch is much wider. This makes it much less useful for determining the ideal pressure.

 

Respectfully disagree, unloaded I'm running 32-35 psi in a Tacoma. Loaded with a camper he needs to bump up that tire pressure. Just be be clear a "camper" is usually a unit that rides in the back of the truck. I notice some people refer to their camper trailer as a "camper" if this is truly the case and he is pulling a camper/trailer then I would still increase the psi due to the added tounge weight. That said, in the bed camper near or close to max tire psi. Pulling a trailer/camper 5-10 psi over daily driving psi.

 

I agree that radials won’t change as much as bias-plys but if i put 30psi in my radial tires and do a chalk test, then test again with 45psi, i’m gonna see a difference in the contact patch...
The test seems to be a pretty useful guide to me anyway, especially if the weight that the tires are normally carrying is anything above the original, standard weight....or if your tires are different than the stock ones....or if you’re towing a heavy load....or if the tire temperatures are super high or super low....

 

I get what you're saying. But, the calculations are based on GAWR, not curb weight. So, the tires will handle anything the truck can carry at the proper tire pressure. If you prefer to up the tire pressure for personal preference, I understand that. But, it's not actually necessary.

 

Googled your tite to be E-load ( at 80 psi) , loadindex 126 is maxload 3750 lbs a tire.
Means that you can drive with 3750 lbs on one tire constant speed of 160kmph/ 99mph , without overheating any part of tire.
Once overheated the tire is lost, but can take 3 years before damagge builded up that far that it blows.

So if you give weights , GAWR's , GVWR, emptyweight , and maximum speed you wont even go over for a minute,I will calculate a safe pressure for it, with an even safer formula then the offical used, I once got hold of, and went running with.

 

I have a camper shell, not a camper. It's fiberglass and not sure what it weighs, but it dropped the OEM suspension about an inch.
I'm going to go ahead with chalk test ONLY to see where it is currently as a reference and then, compare to see how the wear looks at my new 35psi (cold) standard. And, it makes sense to have the tires at temp, say after my 45 min commute home? I'll get it done when it's not raining this week.

 

No. Tire pressure should always be measured cold.