Tire PSI and truck camper question

[robertjp]

My question is if the truck manufacturer (Chevy) says the max psi should be 35 (on the sticker) and on the tire it says 51 max psi, would it be ok to increase the pressure from 35 to say 45ish to account for the truck camper? Im assuming 35 is too low even if it only weighs 1400 lbs dry.?? Thanks in advance. Bob

[Kayteg1]

lawrosa wrote:

Kayteg1 wrote:
I know all the forum whining can get confusing, but I don't see anything confusing in following manufacturer recommendation.

Here is the page GoodYear sends.

Those charts are for LT tires!!!! The OP has P rated tires.... It dont apply.

I also gave simple rule of thumb for tire inflation like 30 replies earlier.
All it takes is ask any 3th grader to do the math.

[lawrosa]

robertjp wrote:
Wow. Im sorry I asked. Im more confused now than when I started. Some yes, some no. I still dont know if I should/could increase the pressure on the back. Yes Goodyear P tires, 35 psi recommended normal, tires 51 psi max. Camper 1394 dry. 2017 Silverado V8 with torklift stabiloads on the back leaf springs. Im not sure what else I know. Thanks again.

Why are you confused? You have P rated tires. Whatever it says on the side wall in regards to weight gets derated some 9% or divided by 1.10

This is how P rated tires work on a truck application.

@ 35 psi your tires can handle 2460/1.10 = 2236 lbs per tire

At any other pressure above 35 psi - 51 psi can handle the same weight 2236 lbs.

Increasing the pressure does nothing in regards to load capacity.

So the most you can put on the rear of the truck in regards to tires is 4472 lbs

Tires are always rated higher then the trucks suspension. And your probably asking this because you feel your overweight?

Lets make you feel safe knowing your within your limits.

What we know

Camper 1394 dry
Tires 4472 for rear total. ( Irrelevant at this point)


What we need to know.

Payload of truck from yellow sticker in the door jam.
Gross rear axle rating from tag on door jam. ( ie: 3900, 3750, etc)

And also open up the glove compartment and tell us what that sticker says for truck campers..

Looks like this..

[lawrosa]

Kayteg1 wrote:
I know all the forum whining can get confusing, but I don't see anything confusing in following manufacturer recommendation.

Here is the page GoodYear sends.

Those charts are for LT tires!!!! The OP has P rated tires.... It dont apply.

[Boatycall]

I say just pump 'em up to 105psi.... mine are. It'll be fine. If I can do it, you can do it.

Another great piece of advice -- never take advice from Boaty after I've had my Makers Mark n Coke for the evening...
:B

[Kayteg1]

Now I am confused Flip 😉
Are you talking about whining, or finding tech spec, or both?

[SidecarFlip]

Kayteg1 wrote:
I know all the forum whining can get confusing, but I don't see anything confusing in following manufacturer recommendation.

Here is the page GoodYear sends.

You are pretty experienced at that...lol:R

[Kayteg1]

I know all the forum whining can get confusing, but I don't see anything confusing in following manufacturer recommendation.

Here is the page GoodYear sends.

[SidecarFlip]

It is corn fusing to say the least....and most.

I just run maximum cold inflation pressure out back (whatever the sidewall says). Never had an issue with that.

[robertjp]

Wow. Im sorry I asked. Im more confused now than when I started. Some yes, some no. I still dont know if I should/could increase the pressure on the back. Yes Goodyear P tires, 35 psi recommended normal, tires 51 psi max. Camper 1394 dry. 2017 Silverado V8 with torklift stabiloads on the back leaf springs. Im not sure what else I know. Thanks again.

[jadatis]

jadatis wrote:
Your tires are most likely Standard load P-tires, and on those they only give maximum allowed cold pressure.
The maximum load of tire can be carried up to 99m/h AT 35 psi , wich is standard reference-pressure for P-tires SL. So if you drive only below 99m/h you may use the 35 psi.

The space between 35psi and 51 psi is used to highen up the referce-pressure ( further AT-pressure) for higher speed then 99m/h with a system depending on speedcode of tire. Also for alighnment camber angle above 2 degr.

LT tires give on sidewall the AT-pressure , and in earlyer days higher was allowed and even adviced upto 10 psi extra, but nowadays the tiremakers dont allow it anymore, and so the AT-pressure is the maximum allowed cold pressure.

So tiremakers allow for SL P-tires a higher pressure then AT, and if you use it to cover some higher load on tire then maximum load, they cant prove you did it for that higher load then max ,that they dont allow, but mother nature will be happy with it.

To high pressure gives that less deflection of tire, that things go bumping, so to high is not bad for the tire, but bad for your kidneys and teeth-fillings.

I seemed to have given a wrong idea, so will add this post.

As long as I did not get comfirmation of exact tire-specifications, I will assume you have P-tires in Standard load.

Those will be even a bit overrated for the gross axle weight rating at rear, wich would even alow a lower pressure then 35 psi.
But I always add 10 % to the real axle load , also for LT tires.
This to cover unequall loading R/L in combination with a bit higher weight then estimated.

If you would weigh the axles, or better seperate axle-ends ( wheels), the inacuracy is already less.

If then the pressure goes over 35 psi , you better fill that, and for P tires its allowed up to 44psi sometimes, and in your case even 51 psi.

For LT-tires the comparable 35psi is given on sidewall and called reference-pressure, but I will call it AT-pressure furtheron.
So AT-pressure(cold) is something else then the maximum cold pressure.
In earlyer days, the tiremakers allowed for LT higher then AT-pressure , but nowadays not anymore.
Strange but true.

But your tires are allowed higher then AT because on sidewall it says so ( AT 35 psi maxcold 51 psi).
but because 35 psi is already with a maximum reserve, the 51 psi would give a terrible discomfort.
For savety of the tires though , 51 psi is never bad, mayby sooner punctures . But if you can give me all the details,mayby the pressure can even be save lower then 35 psi.

[lawrosa]

Grit dog wrote:

lawrosa wrote:

Grit dog wrote:
Yes you can air up to what the tire says.
Your little camper will be about 2000lbs if your lucky. Get any flavor of load range E tires so you can stiffen up the back. Will be a much better ride in your half ton. And you can air back down to 35psi when you don't have the camper.

Isnt that bad advice telling him to put a load range E on a truck with P rated tires ( most likely) and rims?

Rims are not rated for those higher pressures, and the idiot at the store will probably not be smart enough to put rigid valve stems on too.

Since you're the tire expert, how do you know the rims aren't rated for a higher pressure? I can't dispute that with Internet data, no can I dispute the 9% de rate thing I guess . Which is also some buried away in the books theory by the tire industry I guess? Also mentioned dropping another 20% to get to the "full time" weight rating vs the "max load" rating. By the time you do all that, the tire won't hold the vehicle itself p, almost. Found a couple articles discussing it, but if it was real, trucks with P tires would come with a big placard on the dash warning that the tire ratings ON the tires was not valid.

Maybe I'm just ignorant and lucky, but I've been putting D or E load tires on half tons for going on 30 years. Even running 60-70-80 psi at times hauling loads way to heavy for the trucks' ratings never popped a rim.

Yours and capris paragraph of theory are akin to the vehicle weight cops except you're tire weight cops.
Unless you can cite some real over inflation catastrophies or something, I'll consider it internet drivel and not be concerned with E tires on my half ton.

Again, some folks on here live in the real world, others will reccomend 1 ton duallies to pull pop up campers.

And FWIW, the new HD Rams have "soft" valve stems with 80 psi tires. Worked fine for years now.

Well im not the tire expert. Only from what I read from the FMVSS..

When P-metric or metric tire are installed on light trucks (SUV, pickup or minivan), the load
rating/capacity of the tire is reduced by a factor of 1.10 as prescribed by the Federal Motor
Vehicle Safety Standards (FMVSS). This load reduction is mandated by Federal motor Vehicle
Safety Standards (571.120). This is based on the expectation that passenger type tires (Pmetric)
tires which are designed mainly for passenger cars may experience more severe use
and overloading when used on light trucks.


https://www.nexentireusa.com/cms_files/original/NEXEN_TIRE_SAFETY_BULLETIN___REPLACING_LT_TIRES_ON_L...

From the FMVSS. Reading 2nd page in states the 1.10 / by


https://www.gpo.gov/fdsys/pkg/CFR-2011-title49-vol6/pdf/CFR-2011-title49-vol6-sec571-120.pdf


The tires even derated must meet the axle rating of the truck.

So the OP's tires @ 35 psi can carry 2236 lbs. Thats 2460/1.10

Thats 4472.

But whats his axle rating?

2000 lbs on a rear thats already at say 2300 lbs your at 4300. Maybe ok for the tire and borderline.

But these chevy axles are rated lower and this is the problem....


Example my truck chevy 1500..

P rated tire sidewall 2535/1.10 = 2304lb tire rating ( 4608)
RAWR 3750.
Cat scale weight @ rear 2300 lbs
RAWR 3750-2300 1450lb payload.

No way can I put a 2000lb TC in my truck bed without going over axle weight.

[Grit_dog]

mkirsch wrote:
It's not that complicated.

What most people are telling you here is that IT DOES NOT MATTER. 35PSI or 51PSI, those P-metric passenger car tires have the SAME LOAD CARRYING CAPACITY.

Try 35PSI and see if you like it. Try 51PSI and see if you like it better or worse. Try some pressures in between.

Unless you are just absolutely nerve-dead, you will know quickly if there are any problems. Use your common sense, TURN AROUND, and limp home if you don't like how things feel.

You're correct, it was determined that tires don't get stronger after 35, BUT they do get stiffer. 35 is a marsh mellow ride compared to 50. Hauling a high CG load like a camper, stiff suspension/chassis/tires rule.

[Grit_dog]

lawrosa wrote:

Grit dog wrote:
Yes you can air up to what the tire says.
Your little camper will be about 2000lbs if your lucky. Get any flavor of load range E tires so you can stiffen up the back. Will be a much better ride in your half ton. And you can air back down to 35psi when you don't have the camper.

Isnt that bad advice telling him to put a load range E on a truck with P rated tires ( most likely) and rims?

Rims are not rated for those higher pressures, and the idiot at the store will probably not be smart enough to put rigid valve stems on too.

Since you're the tire expert, how do you know the rims aren't rated for a higher pressure? I can't dispute that with Internet data, no can I dispute the 9% de rate thing I guess . Which is also some buried away in the books theory by the tire industry I guess? Also mentioned dropping another 20% to get to the "full time" weight rating vs the "max load" rating. By the time you do all that, the tire won't hold the vehicle itself p, almost. Found a couple articles discussing it, but if it was real, trucks with P tires would come with a big placard on the dash warning that the tire ratings ON the tires was not valid.

Maybe I'm just ignorant and lucky, but I've been putting D or E load tires on half tons for going on 30 years. Even running 60-70-80 psi at times hauling loads way to heavy for the trucks' ratings never popped a rim.

Yours and capris paragraph of theory are akin to the vehicle weight cops except you're tire weight cops.
Unless you can cite some real over inflation catastrophies or something, I'll consider it internet drivel and not be concerned with E tires on my half ton.

Again, some folks on here live in the real world, others will reccomend 1 ton duallies to pull pop up campers.

And FWIW, the new HD Rams have "soft" valve stems with 80 psi tires. Worked fine for years now.

[robertjp]

Yeah Im going to put 51 psi cold on the back and leave the front at 35. After reading all that it is confusing. Hope that is the right thing. Thank you