OK, Tire Gurus Tell Me....

[ShadowsPapa]

Where does it say max? Take a look at this Gladiator door sticker - 38psi - nothing about max inflation.
That 38 us what you should run in this case - according to the stick. There's no max to it.
The TIRE sidewall will give max inflation for that tire for the max load stated on the tire - that is not truck max but TIRE max.
Please show where it says tire max here -

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[ShadowsPapa]

You are saying put more psi than max at max load? That doesn’t seem correct to me.

Where are you getting MAX inflation on the door sticker?????

 

[Gladman]

Where are you getting MAX inflation on the door sticker?????

I will check mine tomorrow. Itlooks different than yours, but let me find out and I’ll post it.
Thanks

 

[CerOf]

http://download1476.mediafire.com/7...vnt/Goodyear_Tire_Inflation___Load_Charts.pdf

This is a chart for Goodyear. I think it’s page 12 that lists the loads for a 35x12.5R17 at various psi’s.
At 35 psi it is effectively a load range c, for me.

 

[CerOf]

You are saying put more psi than max at max load? That doesn’t seem correct to me.

The door jamb is not the max.

the “max” that you should never exceed is what is on the tire’s actual side wall.

 

[Gladman]

6. MAXIMUM LOAD AND COLD TIRE INFLATION
Finally, in the area of the sidewall closest to the wheel, you’ll find the tire’s load capacity and its maximum cold inflation pressure. This might be different from the inflation pressure recommended for your vehicle by its manufacturer. That’s because the maximum cold tire inflation pressure stated on the sidewall only indicates the greatest pressure permitted for that tire. It doesn’t state the optimal pressure for a tire mounted on a particular vehicle – that is found on a placard mounted on the vehicle or in its owner’s manual.

I got this from the Bridgestone tire site. It gives more clarity, but it would seem that adjusting psi based on loading would be still be a chalk test venture. I will experiment with this.

 

[CerOf]

6. MAXIMUM LOAD AND COLD TIRE INFLATION
Finally, in the area of the sidewall closest to the wheel, you’ll find the tire’s load capacity and its maximum cold inflation pressure. This might be different from the inflation pressure recommended for your vehicle by its manufacturer. That’s because the maximum cold tire inflation pressure stated on the sidewall only indicates the greatest pressure permitted for that tire. It doesn’t state the optimal pressure for a tire mounted on a particular vehicle – that is found on a placard mounted on the vehicle or in its owner’s manual.

I got this from the Bridgestone tire site. It gives more clarity, but it would seem that adjusting psi based on loading would be still be a chalk test venture. I will experiment with this.

It is a chalk test venture if you have tires other than stock.

other factors go in to it though, such as rim width, tire width, etc

chalk test does NOT dictate loading.

High speeds generate heat.
Under inflation generates heat.
Towing or hauling generates heat.

heat in a tire can cause bad things.

 

[TrainMan]

These threads confuse me. If the door says 38psi for stock tires, I keep them at 38. Now my highly scientific method is to drop 2lbs for each size increase as a starting point, then do chalk test and handling test.

 

[Gladman]

Not quite up to the 17000 opinions I predicted... Bummer. Total bummer. Back to work.

Patience, Grasshopper.

 

[Gladman]

These threads confuse me. If the door says 38psi for stock tires, I keep them at 38. Now my highly scientific method is to drop 2lbs for each size increase as a starting point, then do chalk test and handling test.

Let me see if I can explain this another way:
Example:
I have a vehicle that has a a tire psi rating on the door sticker of 38 for all 4 corners.
The vehicle is usually driven with little weight in it so 38 psi on the tires is essentially unloaded.
I put the max load capacity in/on the vehicle which adds about 1200 lbs. Do I add psi to the tires to the max psi rating shown on the tire, or leave it as the door sticker show?
I fail to understand how the tire is supposed to perform optimally at a single psi rating for different loads. Therefore my original question dealt with this type of scenario, if this was a logical conclusion.
Thanks,

 

[CerOf]

You’ll need to look up the specs for that tire.
To make it easy, go by discount tire and ask them what psi for a given load.

 

[Higher_Ground]

Do people actually inflate their tires when hauling a load? Does the distance or time spent hauling factor in?

Just thinking out loud, but 4 larger than average adults is ~800 lbs and that's not nothing. But have you ever heard of someone stopping by the filling station to inflate their tires or deflate them based on having 3 passengers inside?

My sticker says 36 psi. I do not have any extra weight in it. Being that it's colder than when I originally filled up they are sitting anywhere from 30 psi to 34 psi when I get inside (30°F vs 55°F) depending on the day of the week.

I realize that under and over inflation are both issues but I also understand that air expands when it heats up. That 34 psi turns to 36 psi once it's running. It's not something that stays constant for long and adjusting it all the time doesn't seem like it would make much of a difference just for a couple PSI up or down.

I don't have a ton of experience with tires this large so maybe that plays into it somewhat.

Either way, I would think that the heat generated driving in 100°F heat on hot asphalt has to be greater than driving a few pounds under recommended inflation in the middle of January.

IOW I don't think it's an exact science and perhaps our ability to measure the inflation pressure easily and accurately tempts us to fiddle with it when we don't need to.

 

[JoseQ_80]

Running a little lower psi also helps with tracking down the road it won't wander around as much.

Start with 2-3 psi colder than the door sticker psi, particularly the front tires. Drive it and see if you notice a difference in wanderlust.

If you are reading this and taking delivery soon (Congratulations) check your pressure right at the lot. They are shipped with 39 psi or more and sometimes the dealer does not air down to the psi on the door sticker.

Flame away

 

[CerOf]

I only go above what’s listed on the door if I’m towing or will have the bed full for a long distance. 6 miles round trip to Lowe’s with a full bed? Naw, I don’t change the pressure

PS look at the tire when you have a load. Does it look “low”? If so, probably needs more air.

 

[Gladman]

Running a little lower psi also helps with tracking down the road it won't wander around as much.

Start with 2-3 psi colder than the door sticker psi, particularly the front tires. Drive it and see if you notice a difference in wanderlust.

If you are reading this and taking delivery soon (Congratulations) check your pressure right at the lot. They are shipped with 39 psi or more and sometimes the dealer does not air down to the psi on the door sticker.

Flame away

Yes to that. Several times on dealer servicing my 4 tires were pumped up to the max 44 psi even though the door sticker indicated 38 rear, 34 front On a GC. I always ran all 4 at 36.

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