Tire Pressure Calculation

[Rogan]

I've got about 5000mi on my Treadwrights now. I had an alignment done when they were installed. I run about 70psi on the steer axle, and 45psi in the duals.They are wearing a little funny, and I can't figure out why. I don't know if it's the softness of the compound, or if it's an alignment or pressure issue..The fronts and rears wear opposite. By that, I mean the front tire lugs wear more on the trailing edge, and the rear tire lugs wear more on the leading edge.

[Wild and Free]

I've got about 5000mi on my Treadwrights now. I had an alignment done when they were installed. I run about 70psi on the steer axle, and 45psi in the duals. They are wearing a little funny, and I can't figure out why. I don't know if it's the softness of the compound, or if it's an alignment or pressure issue.. The fronts and rears wear opposite. By that, I mean the front tire lugs wear more on the trailing edge, and the rear tire lugs wear more on the leading edge.

Why so hard on the steers? I never run over 50 psi on my steers even with the ranch hand bumper on all my rigs and have never seen funny wear an either of my cummins or even my V10.

[Rogan]

They seem to balloon out if I run lower. I was running them around 60, but the sidewalls looked to be really bulgy at the ground surface.I'll see if I can go out at lunch and snap a couple pics of the tire wear.

[Wild and Free]

That's what a radial is supposed to look like.

[Rogan]

agreed, but it looked a little puffier than normal.

[dorkweed]

This has been a great thread!!! Rogan..........with only 5k miles on your retreads, maybe the tread hasn't "cured" yet???? Don't all new tires feel squirmy and/or wear funny until they get a certain amount of heating/cooling cycles in them???John..............Just was playing "devil's advocate" with you!!! I know you always have a great answer for everything!!!I'll be heading up to NoDak two weeks from tomorrow......Oct. 4. Three guys, 3 dogs with assorted gear in my truck. The rest of our gear is getting hauled up in a 6x10 cargo trailer behind my truck. Normally we have 4 guys and 2 vehicles going.................so the trailer will be on the truck up and down the gravel roads in NoDak all the time probably. I'll watch my tires. As you probably know, I run 70psi all the time...................I just don't want to fart around airing up and down all the time. My tires don't wear funny at all..............nice and even. I just rotated my tires last week, greased everything that has a zirk, changed oil, oil filters, fuel filters, air filter and CC breather filter. I'll post how everything goes up there.

[AH64ID]

This has been a great thread!!! Rogan..........with only 5k miles on your retreads, maybe the tread hasn't "cured" yet???? Don't all new tires feel squirmy and/or wear funny until they get a certain amount of heating/cooling cycles in them??? John..............Just was playing "devil's advocate" with you!!! I know you always have a great answer for everything!!! I'll be heading up to NoDak two weeks from tomorrow......Oct. 4. Three guys, 3 dogs with assorted gear in my truck. The rest of our gear is getting hauled up in a 6x10 cargo trailer behind my truck. Normally we have 4 guys and 2 vehicles going.................so the trailer will be on the truck up and down the gravel roads in NoDak all the time probably. I'll watch my tires. As you probably know, I run 70psi all the time...................I just don't want to fart around airing up and down all the time. My tires don't wear funny at all..............nice and even. I just rotated my tires last week, greased everything that has a zirk, changed oil, oil filters, fuel filters, air filter and CC breather filter. I'll post how everything goes up there.

It is a great discussion, and always nice to see real numbers from people who don't embellish. I'd love to get tire wear like yours, but I am not willing to sacrifice a life style

[Mopar1973Man]

I'd love to get tire wear like yours, but I am not willing to sacrifice a life style

Don't I wish. I would love to get his type of tire wear but sure not going to happen with the things I have to do with my truck.

[ISX]

Most of my driving is about 50% gravel, drive 35 miles of it daily to and from work and it does wear tires a bit faster but it comes out to about the same wear as if loaded with trailer most of the time on hot pavement from my experience with all my rigs. Ryan the Hankook Dynapro ATM are going good on my cummins and I have talked to many others who are running them and all in my area are having great luck with them. I have 30K miles on the set now and they are still look almost new.

I know a lot of people with feathering issues with them, including me. Idk why they suck on my truck but they just do. The michelins all wear fine. Must be a missouri thing.

[dripley]

It is a great discussion, and always nice to see real numbers from people who don't embellish. I'd love to get tire wear like yours, but I am not willing to sacrifice a life style

It is a great discussion. I have seen people claim the mileage Dorkweed is getting. Not knowing them made the info doubtful. I do feel I am seeing honest numbers here. I too wish I could get the same numbers but I dont think after 12 years I will see any change. I just drive the way I drive.

[Mopar1973Man]

I know I'm reviving a old thread but I've updated the formula page with correct dual formula so people with dually rear axles can calculate proper pressures now.

Show a demo of Formula vs. Table pressures from Michellin.

Axle Weight: 4,850# on Single Tire Axle

Single Tire Forumla: (Axle Weight / 2) / Tire Capacity weight x Tire Max Pressure = Inflation Pressure

(4,850# / 2) = 2,425# / 3,042# = 0.79 x 80 PSI = 63.7 PSI

Axle Weight: 8,820# On Duals Rear Axle

Dual Rear Tires Formula: (Axle Weight / 2) / (Tire Capacity weight x 2) x Tire Max Pressure = Inflation Pressure

(8,820 / 2) = 4,410# / (2778# x 2 = 5,556#) = 0.79 x 80 = 63.4 PSI

Take note on duals tire axles you got to double the 2,778# rating of the tire and then divide your axle weight. But with both sets the pressure number is right there within 3 PSI of the tire pressure chart of Michellin.

[jdeng]

Somewhere I saw another formula for figuring inflation pressure that used the section height of the tire.  Supposedly, a correctly inflated tire will have a loaded section height (rim to ground) of some percentage of its unloaded section height. 

 

And of course, I can't find that anymore.  Ever heard of doing it that way?

[joecool911]

My tires are wearing more in the middle that outside. I've been running 55psi all round. Need to find a scale!

[Mopar1973Man]

On my 1996 Dodge Ram 1500 its 43 PSI in the front and 27 PSI in the rear. Absolutely flat wear on the tires.

 

On the 2002 Dodge Ram 2500 its 57 PSI in the front and 37 PSI in the rear. Also flat wear across the tires. Now towing I just inflate the rear to 57-60 PSI I'm golden.