PSI suggestions and E rated tires

Hello all,


I run stock tires 275/65r18.

I have E rated tires and what do y’all run PSI wise for just driving around town compared to towing?

I have Falken Wildpeak AT4W


Thanks!

 

I have bfgs in E load. I run 38 up front and 33 in the rear. Chalk patch is good. I like to have more traction. Also I live in socal so with the heat and driving 15 minutes the psi can go up by 3 or 4 psi.

 

On my 14’ CrewMax I have E rated BF Goodrich A/T KO2’s. BF Goodrich recommends 43PSI in the front and 46PSI in the rear for my setup.

I chose E rated for some extra flat protection however it rides like something the Flintstone’s would use.

 

The math puts it somewhere around 40psi per tire, I think that tire is somewhere around 3,000 lbs @ 80psi. Truck is about 6,000 lbs. so that's 1,500 lbs per tire which is ~ 40 psi.

 

Suggested psi for rear assumes a load most of the time on calculators. Without a load its much lighter back there compared to front so a high psi will be very bouncy. I suggest starting low and going up from there for comfort.

 

You calculate it based on the load you expect - I'm not doubting you could go lower for a squishier ride, but the tire is rated for 1,500 lbs @ 40psi

 

Can you link the calculator? This is very helpful! I was running way too low, I went with the plackard inside the door frame. I need to pump up my tires some.

 

I had 285/55/20 KOs on my 2014 when new.
The sticker reads 49 PSI, I ran 42.

 

I didn’t use a calculator—just did the math. It’s pretty simple and here’s how you can do it too:

How to Calculate Tire Pressure Manually

1. Find your tire’s max load and max pressure
(This is on the tire sidewall)
Example: Max load = 3,000 lbs @ 80 psi


2. Figure out how much weight each tire is carrying (Actual Load)
Example: If your truck weighs 6,000 lbs and has 4 tires, that’s 1,500 lbs per tire


3. Use this formula:
(Actual Load ÷ Max Load) × Max Pressure = Required Pressure
In this case:
(1500 ÷ 3000) × 80 = 40 psi



So, for 1,500 lbs per tire and a tire rated for 3,000 lbs @ 80 psi, you'd need about 40 psi.

This gives you a good baseline. You can tweak from there based on how the truck feels or handles, but it’ll get you in the right range.

 

Is that a TRD Sport?

 

45psi. Although I recently bumped to 60 and have no complaints. Got an extra MPG towing.

 

No, it was a Gulf States TSS package.
Just a bunch of cosmetic BS, most I've since removed or replaced, everything but the wheels.

 

Not to convolute the conversation but I run 295/70R18 Nitto Ridge Grapplers in E rated form at 40 psi. It’s a good compromise between mileage and comfort, and they wear pretty decent. Last set I got 58k out of.

 

So here is what the Falken site says for PSI and my tire.

kinda odd, maybe I need to air down then?

 

Someone check me on this, could be wrong here

 

Unfortunately, that isn't correct. While your maths are fine, you made some incorrect assumptions about the linearity of air pressure in a tire vs load handling. You also made some incorrect assumptions about equal weight distribution fore and aft on the vehicle's axles and tires.

The 'airspring' of a pneumatic tire has a linear range, but is not linear throughout the entire range of inflation. If I'm not mistaken, Michelin, Toyo, and a few other MFG's have a white paper documenting this. Essentially, you need a minimum inflation pressure to start supporting a load (or rather, to a achieve a load rating), and after that minimum inflation pressure, the tire pressure behaves more or less in a linear fashion. Within that range, the tire achieves acceptable deflection of the carcass, heat retention and shedding, and loading characteristics to be deemed safe by the tire manufacture.

Review this document from Toyo Tires: https://www.toyotires.com/media/pxcjubjs/application_of_load_inflation_tables_20200723.pdf

The correct way to determine the inflation pressure for a tire of size or load rating different than that on the vehicle placard (assuming you aren't using a generic tire inflation calculator) is:

- First, reference the tire size, load rating, and pressure indicated on the vehicle placard. We'll call the two items your Old Tire Size and Old Inflation Pressure
- Locate the tire size on the inflation table listed above
- Coordinate the top row of inflation pressures with the tire size and your listed inflation table on the placard, and note the associated load in the table. We'll call this your Old Load. If you're inflation pressure is between two listed pressures, you can use your maths to linearly interpolate the load
- If you tire is a P rated tire being used on a pickup truck, derate the Old Load by 10%

- Now find your New Tire Size/Ply rating on the inflation table
- Scan to the right of that tire size until you see a New Load number that matches your Old Load number. In other words: New Load = Old Load
- Scan up to the inflation pressure row above the New Load to realize your New Inflation Pressure.
- As with before, if your New Load is between two pressures listed, use your maths to determine the correct pressure.

If memory serves, a stock size LT275/65R18 is going to require around 42 or 43 PSI to match your 33 psi rear tire rating.

But, a note about inflation pressures: OE manufactures spec the minimum pressure to support the maximum axle weight listed on the door jamb in order to achieve the softest ride safely. But those pressures can be manipulated a few pounds either way. @Mad Max for example, runs less pressure in is LT rated tires than is technically required which on an LT caracass rarely causes an issue with tire wear so long as the load on the axle remains close to the unladen weight. He's also able to run less pressure in the rear tires because in an empty pickup truck, you have closer to a 60/40 weight distribution front to back axle.

I, on the other hand, always run MORE pressure than the bare minimum because I am always hauling stuff in the bed or towing a trailer and prefer my tires to be responsive, and be able to shoulder a heavy load without the need to inflate the tires.

 

Cool calculator. Gets you pretty close or baseline anyway.

 

Draw a chalk line on the tire and drive forward and backward a bit. If the outside edges wear then inflate. If just the inside wears then deflate. Once it wears evenly you are done.

 

In all honesty I was fascinated to learn that Toyota spec’ed a Tundra with E rated tires…the nerd in me was interested.

 

Interesting that this thread comes up now, as I was just about to post the same thing.

I went from OEM Michelins to E-range Toyo AT3's in stock size.

I just reached out to Toyo with my vitals; Size, truck, door sticker, etc. and got back to me very quickly with a recommendation. Glad I checked 'cuz I was a few lbs. under inflated.

Per Toyo Technical:

Bruce,

Based off the information provide: OEM P275/65R18 114 30/33psi vs new tires LT275/65R18 123. New tires should run 42/45psi.

Toyo Tires U.S.A. Corp.

 

Thanks for the detailed writeup - you are right that you want to consider total axle weight - and that's a good idea to consider the vehicle load rating.

 

That’s awesome!


How you liking the Toyos? Quiet?

 

Amazing write up!

so why does a LT tire need more air to match its P rated brother?


I am wanting to understand the science of it more, is it cause it’s just more rubber?

 

My not so scientific answer - think of it like the thickness of a ballon - a really thick balloon (e or f rated) is going to take more pressure to act like a normal balloon than a thinner balloon (p-rated). In other words a heavier tire needs more pressure to support it.

 

I think you are close. As I understand it, LT tires are designed to not only support more weight, but put up with more abuse while doing so. Thicker and sometimes more body plies, thicker shoulders and sidewalls, more cords in the bead to maintain a seated bead at higher pressure, deeper tread - these all allow the tire to carry more weight as well as be more robust in off pavement or rough service situations, day in and day out. P rated tires simply are not designed to be as robust or to be loaded up to max every day.

But that’s not all…! Tire load used to be rated by the number of physical plies used in the construction of the tire. P rated are equivalent to 4 plies; C rated 6 plies; D rated 8 plies; E rated 10 plies; and so on. Tire construction has advanced much since then and LT tires often use better/thicker/stronger materials to construct the plies instead of simply adding more layers to achieve the same overall strength and load capacity. Some p rated and LT rated tires have the exact same number of plies, but differ greatly in materials and thickness.

But why for?

HEAT. HEAT. And more HEAT.

Heat is generated in tire as the tire contacts a friction surface, but also internally as the plies deform to create a contact patch with the ground. If you were to measure the overall height of an inflated tire that hasn’t been mounted on the vehicle, then compare it to the same tire with the weight of the vehicle resting on it, the mounted tire would be shorter. Add some air and it will get taller; take some air out and it will get shorter. The carcass is deforming as pressure/weight is applied to. Add more weight and you get more deformation. Add more/thicker plies with the same air pressure and your overall deformation will be the same, but the material is deforming more, generating more heat.

Thus, more air pressure is required for the same load rating, so-as to minimize internal heat production in the tire.

While the materials in an LT tire are designed to deal with constant heat from higher loads much better than it’s p rated brethren, we still want to minimize the heat production to begin with. Because in the end, once you overheat a tire, bad things happen, no matter how well it’s buit.

Take the infamous Ford Explorer Firestone debacle of the ‘90’s. Firestone MAY have had a smal batch of bad tires, but Ford spec’d those tires at 26psi or less. Yes, 26 psi. I owned one and remember loooong at the door sticker thinking ‘that can’t be right…?’ Explorers were heavy body on frame vehicles that had lots of room for gear and people - I.e - excess weight. People wanted more comfortable riding SUV’s than the full-size solid axle rigs of yesteryear. Speed limits were increasing on the highways and freeways. All of these things factored in to the issue of creating excess heat in the tires, and KABLOOEY! Firestone’s were exploding left and right! Ford tied it up in court for years and pinned it on Firestone when, IMO, in reality it was their under inflated tire spec from the factory.

 

wow that was detailed... well said. Makes alot of sense. Was there supposed to be a "not" in the quoted sentence?

 

Thanks for sharing. BF Goodrich and Toyo recommendations are within 1 psi of each other.

 

Search FoS or Factor of Safety on this site.

You can also email Falken and they'll reply with a few questions about stock tires size and inflation as well as vehicle weight. If you tow, know your axle weights for that, too. They'll return a table for you with the different options for you to decide/try.

Chalk test will confirm it's right for your truck.

Enjoy

 

Yup. Guess I should proof read my posts... Thanks!

 

You're welcome.

@Tripleconpanna posted this in another identical thread, and it's accurate. It gave me the exact same pressures as I got direct from Toyo.