Tire pressure

All sources say that the conversion of 1.1 is when putting P tires on a Light Truck and is already done by the vehicle manufacturer. So Toyota has already factored in the 1.1. This makes sense when you consider that a P tire often doesn’t offer the same load capacity so extra care is needed when converting to a lower rated tire.

Did you read the bulletin from Nitto


“Load Comparison Example, P vs. LT:
P265/75R16 114 Max Load = 2,601 lbs. @ 35 PSI
In order to carry the equivalent load, a LT265/75R16 Load Range C must be inflated to 50 PSI.
Using this example, even LT265/75R16 Load Range D, or E must be inflated to 50 PSI to carry the P-metric load at 35 PSI. LT tires do not offer any benefits of being "heavy duty" when under- inflated.”

“When a P-metric tire is installed as OE on light trucks, the load rating is reduced by a factor of 1.10 by the vehicle manufacturer. This load reduction is mandated by Federal Motor Vehicle Safety Standards (571.120). One reason for this includes the expectation that P-metric tires which are designed mainly for passenger cars, may experience more severe service on light trucks.”

Check out page 11 Toyo offers a great example.

https://www.toyotires.com/media/2125/application_of_load_inflation_tables_20170203.pdf

According to TRA inflation tables:
P265/70/16 @ 29psi is 2216
The conversion was already made for P by Toyota which is 2216 so an LT tire must meet or exceed 2216 therefore:
LT265/70/16 @50 psi is 2335

Closet I could find on the tables was an LT295/75/16 @35 psi is 2240

EDIT: sorry was editing this post like a billion times

 

Toyota did factor it in; it's 2,149-2,172 lbs on a P-metric or ISO/ERTRO-metric tire.

SR/SR5-P245/75/16 109SL @ 32psi=2,172 lb
Offroad-265/70/16 112SL @ 30psi=2,149 lb
Sport-P265/65/17 110SL @ 29psi=2,149 lb

The Offroad OEM tire is a ISO/ERTRO/euro-metric with a load rating of 112SL; not a P-metric. You need to use page 28 of the Toyo pdf to calculate it correctly.
The SR and Sport OEM tires are P-metric.

After reducing by a factor of 1.1; it's 1,954 lbs for an LT.

All my info is in line with Nitto, Toyo, etc. I respectfully suggest your understanding and calculations are a little off.

 

Filled in your given GAWR's and Ptire 114 li in my made calculator, and came to F 21 psi and rear 26psi.
Added F5% and R 18% to cover R oveeloading and R/L unballance.
Then it calculates with an even safer formula then the European official used.

In theory if everything 100% accurate, you can drive 99mph fully loaded, without overheating any part of rubber of tire.

So this explains the bumping, my conclusion in first post was right.

Edit: but check tire-specifications on sidewall, and let me know if different.

 

Always better to guess than confirm with a simple test.

 

dayum, somebody is focused on the real world here? not just a bunch of endless spec talk? could it be true?

 

Ok awesome just making sure I’m reading everything correctly from there. I appreciate the discussion as I was not looking at page 28 which changes things. Thanks for pointing that out.

 

X2. I set my psi with chalk. I adjust pressure for load on longer trips.

 

After months of research I just flipped my LT275/70E18 BFG's (@ 65,000kms) to P275/65R18 B/S Revo 3's. The BFG's were set at a number of different pressures but 35 PSI was best. I was never able to get any kind of ride quality or MPG from the BFG's and that is to be expected given the lift and oversize.

I was going back and forth between the P rated Toyo O/C AW and the Revo's. So far Im very impressed with the Revo's at 32PSI. Ride quality far superior and NOISE has been almost eliminated. Over 45,000 kms (1 year) i had the BFG's balanced at each rotation and they just would not behave. Glad to be rid of them....balance on Revo's is perfect !!!!!

Im going to try running the Revo's at 32F - 29R as i only run with about 100 lbs of trail tools in the box.

On a side note, tire shop somehow damaged (marked) all 4 wheels with a touchless tire machine! There are 3 of these marks on each wheel!

Still have to resolve that .... Oh Joy

 

These things are on a label?

 

Anyone recommend a tire pressure for a basically stock 16 TRD OR DBLCB with 265/75/16 AT3 Falken Wildpeak SL...?
Currently set at 32 cold from the tire shop.

 

Chalk test! why ask for a recommendation from some armchair guy on the internet? your truck will tell you the exact truth. takes 10 mins or less.

 

So basically draw a chalk line across the tire and drive it to see the how it wears ..?
Is this done with cold pressure ..?

 

you can do it warm or cold and both will give you info. i prefer a bit warm so the tire complies with the road and you'll see how it sits and settles well. mark a patch on top of your tires all the way to the sides. then drive the truck a few feet to roll on the chalk patch. inspect chalk patch and you'll see how you sit at that pressure, and if you have lighter or full contact in different parts of that marked patch on your tire. if you run firmer tires that will show very different whether cold or warm. huge difference on mine between cold & warm because i run small size E loads.

 

Mine. At 38-42 based on temp outside.

 

So do it warm and look for the chalk line to have even wear ..?

 

yes. even wear across the whole marked patch.

 

mine says 32 psi all around on the doorjam but i find even 32 is too much for the rear when empty. 28-30 seems to be the sweet spot for the rear with an empty bed otherwise i bounce around all over the place.

 

Update, have been running 33-34F and 31-32R and tires are wearing perfectly. 3 1/2 years of ownership. Even a visual look at the tires should show a slight bulge on the sidewall where the tire meets the road.