What tire pressure to run?

Dick_B wrote:
When such questions arise I often wonder how does the door sticker know what tires are on the vehicle if the OEM tires have been replaced by another make/model tire?

It knows because the tire size is listed there as well, and the load carrying capacity for a given size is standardized by the tire standardizing organizations, such as the Tire and Rim Association. Every tire manufacturer agrees to those standards, so it doesn't matter who makes the tire or where it is made.

But change tire size and the pressure value has to be recalculated.

Oh, and the letters on a tire are part of the *size*. An LT tire is different than a P type tire, and even though the numbers may be the same, the pressures would be different (by 15 psi)

I run my Superduty Michelin LTX MS2 tires at door sticker pressures, 80 rear, 65 front. If I have no plans to tow any time soon, I sometimes lower my rears to 65 also since there is little weight on them.

1ofmany wrote:
OK, let's get out the slide rule and a couple of calculators...and adjust for sea level and ambient temperature...just kidding, run at max pressure and you will not run the very real risk of running on underinflated tires.

:S

No now most likley unless fully loaded you are running your tires OVER-INFLATED, which in order of importance will cause
LESS traction for turning and braking!
LESS tire life as they will wear in the center.
The feeling of riding on rocks!

Assuming you have OEM size tires and are within your ratings the door sticker is fine. Although I prefer to add 5 to 10 over that amount not to exceed the sidewall max.

My truck came with 245/75/17 tires that the door sticker says 75 frt/ 80 rear. I now have 285/70/17 Nitto's. An email from Nitto states I should now run 61 psi front and 65 psi rear when unloaded. I'll bump up the pressure a bit depending on the load.

So my tires are Michelin LTX MS2 tires, size 245/75/R16.

The door sticker calls for 245/75/R16E tires. To be run at 60psi Front and 80psi rear.

Here are my weights from last year. I need to get current ones.
1) Loaded Van with no Trailer
Front Axle - 3,220 lbs (73% of GAWR): 1610lbs / tire
Rear Axle - 3,920 lbs (64% of GAWR): 1960lbs / tire


2) Loaded Van with loaded trailer
Front Axle - 3,380 lbs (77% of GAWR): 1690lbs / tire
Rear Axle - 4,740 lbs (78% of GAWR): 2370lbs / tire

rhagfo wrote:

1ofmany wrote:
OK, let's get out the slide rule and a couple of calculators...and adjust for sea level and ambient temperature...just kidding, run at max pressure and you will not run the very real risk of running on underinflated tires.

:S

No now most likley unless fully loaded you are running your tires OVER-INFLATED, which in order of importance will cause
LESS traction for turning and braking!
LESS tire life as they will wear in the center.
The feeling of riding on rocks!

Well, there you go....

The LeRoys wrote:
So my tires are Michelin LTX MS2 tires, size 245/75/R16.

The door sticker calls for 245/75/R16E tires. To be run at 60psi Front and 80psi rear.

Here are my weights from last year. I need to get current ones.
1) Loaded Van with no Trailer
Front Axle - 3,220 lbs (73% of GAWR): 1610lbs / tire
Rear Axle - 3,920 lbs (64% of GAWR): 1960lbs / tire


2) Loaded Van with loaded trailer
Front Axle - 3,380 lbs (77% of GAWR): 1690lbs / tire
Rear Axle - 4,740 lbs (78% of GAWR): 2370lbs / tire

Well the 245/75-16E are rated at 3,042# each, so to carry a bit further.

Unloaded
Front 1,610# = 52 percent of tire capacity
Rear 1,960# = 64 percent of tire capacity

Loaded
Front 1,690# = 56 percent of tire capacity
Rear 2,370# = 78 percent of tire capacity

Keep in mind you are only running 78 percent of the axle rating, the 80 psi is for the axles GAWR likely 6,084#.

I don't have a current link to an inflation table, but at that load 65 psi to 70 psi would give you the best contact patch from your tire.
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