Tire pressure? 31x10.5 x R15LT F150 supercab

[Cup of Joe]

I went, I looked, I see your point. You replaced the shocks which was most likely your only problem. Have a tire shop do a courtesy check of the suspension and move on. OEM for your truck is either 245/70/16 265/75/16 or 275/75/17 strictly looking at tirerack. I don't see a problem in that case.

Perhaps you should look at the placard again it could be a listing for the spare.

265/75R16 OEM

 

[CapriRacer]

Originally Posted By: vance1
So let me get this straight. Some people actually have a different size tire than what the placard states. I have just been severly chastised over in the maintinence forum for putting a truck on the road that I just bought that the placard calls for tires with 41 psi and the tires that are on it call for 35 max psi. It is a 2000 Dodge Ram 1500 4x4. The placard states I think p225/75r16 at 41psi and the truck has Toyo Open Country A/T 265/75r16 35 max psi. So who is right or am I just an idiot? Do not answer the last part of that question. My post is in the maintinence forum under very dangerous tire bounce.


Vance,

There's a couple of pieces missing to this puzzle.

Here's what I have been able to gather:

Placard say P225/75R16 XL inflated to 41 psi. (Tire Guides says this is correct.)

Tire on there now: 265/75R16, which you've said has 35 psi max written on the sidewall.

So here's the math: A P225/75R16 has a load carrying capacity of 2094# at 41 psi.

A 265/75R16 has a load carrying capacity of ..... well ...... It's a little unclear whether this is a P metric or not. Let's assume it is - so 2601 # is the load carrying capacity.

But you could afford to reduce the pressure to 26 psi and still have more than enough load carrying capacity.

OK, for those sharp eyed readers who just wait for me to make a mistake - None of the loads listed in the post have been reduced by 10% for usage on a Light Truck.

 

[Cup of Joe]

Thanks Carpi

What if the current tires are LT instead of P metric which it appears they maybe?

 

[vance1]

What info do I need to get to you to let me know what pressure to put in the tires. When I saw the 41 psi on the placard I inflated the psi to the 35 max psi as stated on the sidewall. Just tell me what I need to do and what psi to inflate to for normal driving, will not be using it for real heavy loads.

 

[XS650]

Originally Posted By: TaterandNoodles
Thanks Carpi

What if the current tires are LT instead of P metric which it appears they maybe?


I've never seen Capri cranky, let alone carpi.

 

[Cup of Joe]

Originally Posted By: XS650
Originally Posted By: TaterandNoodles
Thanks Carpi

What if the current tires are LT instead of P metric which it appears they maybe?


I've never seen Capri cranky, let alone carpi.


Doh

 

[vance1]

CapriRacer
tires on vehicle- Toyo Open Country A/T P265/75R16 114S M+S DSOC II Max load 2601 pounds standard load at 240 kp 35psi max

placard- Front GAWR 3806 pounds with tires P225/75R16XL Rims at 16x7 41 psi rear is the same. Hope this helps in the equation. Some of these thigs I have no idea what they mean.

 

[CapriRacer]

Originally Posted By: TaterandNoodles
Thanks Carpi

What if the current tires are LT instead of P metric which it appears they maybe?


Tater,

There are a couple of different conversations going on here and I'm losing track of which one we are on - so bear with me.

In your case: Placard says P265/75R15 30 psi using 31x10.50r15LT = 45 psi.

In Vance's case: Well, it's a moot point as he has indicated the tire is a P metric, not an LT metric.

 

[CapriRacer]

Originally Posted By: vance1
CapriRacer
tires on vehicle- Toyo Open Country A/T P265/75R16 114S M+S DSOC II Max load 2601 pounds standard load at 240 kp 35psi max

placard- Front GAWR 3806 pounds with tires P225/75R16XL Rims at 16x7 41 psi rear is the same. Hope this helps in the equation. Some of these thigs I have no idea what they mean.


OK, I'll try to explain. If this gets sounding a bit condescending, I hope you will forgive me. I'm not sure what you know and what you don't, so I'm going to do it all.

P265/75R16: That's obviously the tire size.

114S: That the service description which consists of the Load Index and the Speed Rating.

M+S: This means it meets the definition of an all season tire.

DSOC II: Not a clue what this is!

Max load 2601 pounds: This is the absolute maximum load that this tire was designed to carry.

standard load: This means the tire is designed for the "Standard Load" conditions - as opposed to the "Extra Load" conditions. Extra load being able to carry more load by using higher pressures.

at 240 kp 35psi max: This connects the max load with the pressure needed to carry that max load. This tire could have easily said: "Max Load 2061, Max pressure 44 psi" And while the pressure number would have been different the meaning would have been exactly the same. BTW kPa is KiloPascals - a metric unit for pressure.

 

[vance1]

So am I correct to take it these tires are fine for the truck since that is what is recomended by Toyo and the tirerack? If so what psi would you suggest for normal use?

 

[CapriRacer]

Originally Posted By: vance1
So am I correct to take it these tires are fine for the truck since that is what is recomended by Toyo and the tirerack? If so what psi would you suggest for normal use?


I'm going to word this very carefully, so notice the shades of meaning.

When I look up your vehicle at Tire Rack, the original tire size (per the placard) does not come up. That means there is an error in their system. I suspect the problem is their source - Tire Guides (which also lists it wrong)

Also, they list other tire sizes (ones different than the placard size) as Original Equipment. This is quite different than a recommendation.

I also went to the Toyo web site and they don't have a way to select a vehicle and get a tire recommendation (or at least I get an error message).

So to answer the first part of your question - "Are the tires OK for the truck?" Very likely. Without thorough testing, it's hard to be sure.

"What pressure?" Well, Dodge applies this size to other models at 35 psi, so that's as good a guideline as I think you'll get without actually doing the testing needed.