285/75R16 Tire Pressure

[Grumpy Grumperson]

I have a 2003 LX with BFG KO2 LT285/75R16 126/123R load range E tires and I’m trying to make sure I’m using the correct tire pressure. I’ve been reading lots of posts on this subject but still not 100% sure.

I’m coming up 35psi based the Toyo Tires Table I see referenced a lot. This is lowest pressure on the chart and dictates that both the front and rear would be the same pressure. This is making me think I did my math incorrectly or misunderstood a core principle here.

https://www.toyotires.com/media/3729/application_of_load_inflation_tables_20200723.pdf

These were the original tires and corresponding tire load limits from the chart.

P275/60R18
29PSI- 2216 lbs.
32PSI- 2326 lbs.

The table says to divide by 1.1 since the manufacturer used P metric tires instead of LT.
These are the adjusted Tire Load Limits for LT tires.

29PSI- 2014 lbs.
32PSI- 2114 lbs.

The LT tire chart lists 35psi for 2130 for LT285/75R16.

There’s also this calculator (I found this after all that math) that gives the same results.
Tire Pressure Calculator - https://tiresize.com/pressure-calculator/

 

[Trunk Monkey]

It's listed by the VIN placard on the door frame, think it's 32 psi. But you can run whatever PSI you want and adjust for ride.

 

[Jack90210]

I have a 2003 LX with BFG KO2 LT285/75R16 126/123R load range E tires and I’m trying to make sure I’m using the correct tire pressure. I’ve been reading lots of posts on this subject but still not 100% sure.

I’m coming up 35psi based the Toyo Tires Table I see referenced a lot. This is lowest pressure on the chart and dictates that both the front and rear would be the same pressure. This is making me think I did my math incorrectly or misunderstood a core principle here.

https://www.toyotires.com/media/3729/application_of_load_inflation_tables_20200723.pdf

These were the original tires and corresponding tire load limits from the chart.

P275/60R18
29PSI- 2216 lbs.
32PSI- 2326 lbs.

The table says to divide by 1.1 since the manufacturer used P metric tires instead of LT.
These are the adjusted Tire Load Limits for LT tires.

29PSI- 2014 lbs.
32PSI- 2114 lbs.

The LT tire chart lists 35psi for 2130 for LT285/75R16.

There’s also this calculator (I found this after all that math) that gives the same results.
Tire Pressure Calculator - https://tiresize.com/pressure-calculator/

I'd say that 35psi would be the absolute minimum pressure for an LT tire in this application, based on the pressure calculator and my experience in seeing many drivers under-inflate their LTs (for on-road/highway use).

DO NOT run the door frame sticker pressure when using LT-rated tires.

This is an excellent PDF authored by Toyo Tires that explains the need to run higher pressure in LT tires than in the P-rated equivalents: https://www.toyotires.com/media/bszlobyw/tsd-12-011_replacing_tires_on_light_trucks.pdf

From the PDF:

"Please note that size-for-size; LT-metric tires require higher air pressure to carry equivalent loads of
P-metric tires, and that any failure to adjust air pressures to achieve the vehicle’s load requirement will result
in tire fatigue and eventual tire failure due to excessive heat build-up."

 

[x8o8drifter]

I'd say that 35psi would be the absolute minimum pressure for an LT tire in this application, based on the pressure calculator and my experience in seeing many drivers under-inflate their LTs (for on-road/highway use).

DO NOT run the door frame sticker pressure when using LT-rated tires.

This is an excellent PDF authored by Toyo Tires that explains the need to run higher pressure in LT tires than in the P-rated equivalents: https://www.toyotires.com/media/bszlobyw/tsd-12-011_replacing_tires_on_light_trucks.pdf

From the PDF:

"Please note that size-for-size; LT-metric tires require higher air pressure to carry equivalent loads of
P-metric tires, and that any failure to adjust air pressures to achieve the vehicle’s load requirement will result
in tire fatigue and eventual tire failure due to excessive heat build-up."

^^^YES
Technically any tire that isn't the OEM one should have you asking the manufacturer what PSI to run.
The door sticker is for the tire that came on the vehicle from the factory and ONLY that one (if its another brand/model it could be different) and with stock weight, which alot of us no longer have.

Email the manufacture of the tire. And make sure to specify if the car isn't stock weight.
They usually have a program that they can punch numbers into and it'll give out what PSI to run the tires at based on the load they are carrying.

 

[FairZ33]

Tiresize.com has a tool for this. Assuming I input everything in correctly, you should be running ~38psi.

 

[hoser]

@Grumpy Grumperson You can inflate anywhere in between 35-38psi on your new tires and you'll be fine. The problem with all these calculations is the 100 came in different tires and different tires came with different specs. The GVWR of the 100 is roughly 6860 lbs and the weight distribution is close to 50:50 when unloaded.

The 16" tire/wheel combo had an effective load tire weight capacity of 2255 lbs @32psi but the 18" tire/wheel combo had an effective load capacity of 2130 lbs. So, we are looking at 2,255x4 =9,020 total or 2,130x4=8,520 for the 18" wheel/tires. Obviously, there is a buffer in there and your loaded weight won't be exactly 50:50 ratio. How much buffer do you want?

But going by your 18" wheel placard. OE tire inflated to 32 psi in the rear we get... new rear LT tire should be inflated to 35psi.

For the front, OE tire is asking for 29psi and therefore the load capacity is 2015lbs.

The calculator will only go down to 35psi because the table only goes down to 35 psi. But going by weight capacity, I would be comfortable running 33psi in the front.

My answer is 35psi all around but if you desire a cushier ride, then go 33psi front / 35 psi in the rear.

 

[x8o8drifter]

Tiresize.com has a tool for this. Assuming I input everything in correctly, you should be running ~38psi.

Yep, got the same, but again people need to remember these are for stock weights.

Dad does this since emailing wasn't a thing back in the day and writing snail mailing something was too much work. (This is a rule of thumb thing)

"To determine the correct air pressure, check the pressure when the tire is cold. Run the tire for several miles (say 100kms) at highway speed. Stop and immediately check the air pressue in the tire.
It should be higher than we cold but no more than 10% higher.
Now here is the hard to believe part. If the pressure is more than 10% higher you must ADD AIR and test again.
For example if you start with 50 psi cold. If the pressure is 60 when hot, you have exceeded the (10%) in this case, 55 psi maximum safe heat build up pressure. You must add air.
In this case I would add 5 psi which would take the tire to 65 psi when hot. After you run the tire again you will find the pressure to actually drop because the tire will run cooler.
The heat build up causes the tire pressure to increase when under inflated. On the other hand, if the 50 psi cold pressure does not change when hot. You have more air than needed. You can remove 5 psi or so and test again when they return to cold. Like the next trip you take."

edit: and of course follow the sidewall and start someplace sensible PSI wise.

 

[Grumpy Grumperson]

@Grumpy Grumperson You can inflate anywhere in between 35-38psi on your new tires and you'll be fine. The problem with all these calculations is the 100 came in different tires and different tires came with different specs. The GVWR of the 100 is roughly 6860 lbs and the weight distribution is close to 50:50 when unloaded.

The 16" tire/wheel combo had an effective load tire weight capacity of 2255 lbs @32psi but the 18" tire/wheel combo had an effective load capacity of 2130 lbs. So, we are looking at 2,255x4 =9,020 total or 2,130x4=8,520 for the 18" wheel/tires. Obviously, there is a buffer in there and your loaded weight won't be exactly 50:50 ratio. How much buffer do you want?

But going by your 18" wheel placard. OE tire inflated to 32 psi in the rear we get... new rear LT tire should be inflated to 35psi.

View attachment 3903199

For the front, OE tire is asking for 29psi and therefore the load capacity is 2015lbs.
View attachment 3903200

The calculator will only go down to 35psi because the table only goes down to 35 psi. But going by weight capacity, I would be comfortable running 33psi in the front.

My answer is 35psi all around but if you desire a cushier ride, then go 33psi front / 35 psi in the rear.

Thanks so much. I'm running 35 on all 4 right now but will play around with it a bit. I'm going to do a fairly long trip soon so I want to make sure I get things dialed in properly.

 

[hoser]

Yep, got the same, but again people need to remember these are for stock weights.

The stated pressure is safe for weight up to GVWR. But if towing, sustained high speed or loaded to GVWR or higher, I'd bump up the pressure by 3psi or so. Hyper-inflated will reduce traction too.