Tire pressure

...ferrari will test what their vehicle needs like all manufacturers will.
They also account for how much tire pressure changes when heat gets into a tire.

I know ours alone in my climate change by about 3psi after driving vs cold. Mine are set to 32psi @ around 10-15 degree ambient temp. After driving for 30min or so they get up to 33 roughly in the rear and 34 in the front depending on turning.
Those PSI's for tires like that are also going to be based highly on speed rating too. at 200+km/h that tire will be getting a lot more heat, given those vehicles are being released for performance.

Your idea of needing 45+ psi is fine if you're in a fully loaded 1/2ton or 3/4ton
but in our dinky little tacomas there is no need for that PSI based on load.

 

It's 37 psI for your particular tire...

What they probably did was take the stock tires weight rating(2,149 lbs @ 29 psi) and used it in the LT load chart. That would make it 43 psi but they just rounded up to 45 psi; chart is increments of 5 psi and 40 psi is not enough.

When using LT tires on a trucks/suv originally equipped with P or ISO-metric you can derate the weight requirement by 1.1
2149/1.1=1954

Your tires attain a weight rating of 1964 lbs at 37 psi.

 

Awesome, thank you very much! I appreciate the info.

 

The manufacturers recommendation is based on a P tire according to my door plate irregardless of what is actually on there which is my point.

I'm the guy that inflates his tires based on tire manufacturer just as Ferrari and every other Formula 1 team inflate there tires based on what Perelli tells them. Ferrari doesn't dictate to Perelli what psi to run and neither does Toyota. No Ferrari does not test for what PSI they need. Perelli tells them what it will be. Period.

The psi on the side of the tire is the max...try to have some common sense. Just cuz you don't like the ride at 50psi does not me you are right. You still have degraded load performance.

I like you Joe but you can't ague with facts provided direct from tire manufacturers.

 

I go by what the ppl who make the tire suggest, is what they do. We've had some lawsuits over this already.

https://en.wikipedia.org/wiki/Firestone_and_Ford_tire_controversy

“Ford, which sets the specifications for the manufacture of its tires, decided to remove air from the tires, lowering the recommended pressure to 26 psi.[9] Low air pressure leads to increased heat; heat can damage the tire”

 

Got Toyo RTs...
E rated 285/70-17s...
Running at 35psi.
You got to remember, the highest PSI setting is for the maximum weight rating which we don't need in these mid-size trucks.

 

I don't know why tire pressure is so difficult.

 

The tires for Ferrari and f1 are a bit different though those are specific. And perelli does tons of testing obviously.

But lt tires are often based on heavier trucks. Yes Toyota might ask what say Goodyear would recommend but that will be given to them based on vehicle weight and gross weight rating. And in my door it says a 112 load index which is a 6 ply c rated lt tire. At 30psi

I agree you'll lose weight capacity at a lower pressure. But I'd add air accordingly.

I've had about 900lbs of copper wire in the bed before at 32psi on my winter tires which are passenger tires and saw little to no increase in compression on the tires. So unless you're overloading your truck the psi isn't needed that high.

It would maximize mpg but the ride is awful.
at 50 psi would be for the max load capacity of that tire and even with full payload our trucks aren't near it unless you're overloaded.
50 still seems way to high for these trucks. Fuck my 2500 work van loaded with material and tools is only at 44psi and it's way heavier than the taco is.

 

You seem to have this down so i have a question i have been googling and googling ... I completely understand converting the P tire to LT lower rate to get PSI. But what about P metric to P metric but just a different size ? Example Stock Tire is P265/65/17 Door says 29 psi but switching to P285/70/17. The new tires are load index 117 Falken Wildpeaks AT3. Would you stick with door or would it be lower since its a wider tires with more surface area ?

 

Link to Toyota load inflation tables.
https://www.google.com/url?sa=t&sou...Vaw0zaHumL9xB01d0CRYFLPCS&cshid=1534809195442

To save your some legwork; our trucks are 2,149 lbs inflated load rating for P and ISO/ERTRO metric(there's a difference) and 1,954 lbs inflated load rating for LTs.
P285/70/17s drop off the chart at 26 psi and I hesitate to extrapolate below that because the charts are not linear in nature.

 

Ok so I am doing it correctly I seen the 26 and couldn’t really figure out below that. I tried and got like 18 figured that didn’t sound right. So would you say run 26 or just stick to the door at 29 ?

 

18 is about right if your extrapolating a load value between 26 and 29 psi...1 psi=47.6 lbs.
As I said, I hesitate to go below that because of the non-linear nature of the charts. Below 26 psi, who knows what 1 psi equates to in load rating.

I'd go with 26 psi.

 

Cool , thanks for you info and reassurance that I know what I am talking about. Nice being able to get someone who understands it and has an another answer besides “chalk test”

 

... I am not sure how much air they put in my tires when I bought them?