What PSI for 275/65/18 LT Tires

[ouzo12]

What is everyone running for their L/T rated tires? My size is above but curious if you anyone is running the recommended 50 psi? Tire Rack had a sale and didnt realize it went with the L/Ts instead of the C rating. I told them to bump it down to 45 psi since I'm mostly suburban school run overlanding these days but I still think its too much. Can I do down to 38 psi and still be ok?

Vredestein Pinca AT

 

[Trunk Monkey]

Think the door jamb recommended PSI from Toyota is like 32-35.

 

[GerLC100]

your door sticker provides info about the tire pressure at max load (and perhaps also with reduced load, not sure...).
But you can put the stock tire size/ rating/ pressure into this tool, put your new setting in there and then it let's you know what you should do (again: for max load)

KO2 tire pressure - psi

Just installed 275-70-18 KO2s on 2005 LX470 factory wheels. The door jamb says 29 front, 32 rear. I currently have it at 29 psi all around. Is that the PSI you would use on these KO2 for daily driving / highway driving?

forum.ih8mud.com

View 1:
You're under full load, with suggested pressure: your tire sits flat, nice, as it's supposed to

View 2:
You're using the door sticker max pressure and running with 2 people: you tire is likely bellied out and you're mainly running on the middle section of your tire. typically not a big deal, most people do it. But your wear will concentrate there, driving might be a bit off, no full traction.
But as mentioned: that's what the standard go to driver is doing

View 3:
you go for the pressure on the sticker and 10% up: you make things under view 2 worse

View 4:
You do the conversion via above tool, look up a tire pressure chart for your specific tire and adjust to manufacturer pressure. This way your tire is more or less flat and as supposed to be.

The flatter the tire and the bigger the area "on the ground" the higher the fuel consumption. So a little "belly" is what I typically do on my cars for long distance trips on the highway (like San Francisco to LA) and then I reduce pressure again.

 

[Manhattan]

Correct me if I'm wrong, but once we move from the OE 275/60/18 SL-rated tires to 275/70/18 E-rated tires... that door sticker is irrelevant. I just had my BFG KO2s rotated yesterday and the shop (Discount Tire) went by the door sticker - 40 psi. I'm assuming that's both a habit and policy. I swear, I can run over a quarter and feel the date.

I've put about 160,000 miles on BFGs (third set) and a lot of those miles at 32 psi. But I keep hearing that E-rated tires HAVE to be run at higher pressures. I get that they CAN be run higher... but why do they have to?

 

[Mike NXP]

Correct me if I'm wrong, but once we move from the OE 275/60/18 SL-rated tires to 275/70/18 E-rated tires... that door sticker is irrelevant. I just had my BFG KO2s rotated yesterday and the shop (Discount Tire) went by the door sticker - 40 psi. I'm assuming that's both a habit and policy. I swear, I can run over a quarter and feel the date.

I've put about 130,000 miles on BFGs (third set) and a lot of those miles at 32 psi. But I keep hearing that E-rated tires HAVE to be run at higher pressures. I get that they CAN be run higher... but why do they have to?

You are correct the door jamb pressure relates to the stock P rated SL tires....If you run door jamb pressures on a non-SL tire then you reduce your total load capacity....

@ouzo12 Instead of listening to my uneducated opinion and everyone's random guesses, click the link below ** I see GerLC100 also tagged this tool. It's very useful

Tire Pressure Calculator

Easy to use tire pressure calculator. Use our tire pressure calculator to calculate the new tire pressure needed when changing tire sizes.

tiresize.com

Enter your stock tire size and rating in the left part. Then enter your new tire size and rating in the right. Every tire range has a specific load rating and pressures relating to it. That tool will take your GVWR and figure out what your new LT tire should be run at to accomplish the same thing.

 

[Jack90210]

DO NOT RUN THE DOORJAMB PRESSURES ON L/T TIRES.

 

[Manhattan]

I played with that site/calculator... came away more confused. I'm going to assume I did something wrong here or all I thought I knew about tires was wrong. School me.
Why is the load rating for the E-rated tire 176 lbs. lower than the SL-rated tire? And obviously related to the first question, why does an E-rated tire need MORE psi than an SL-rated tire.

 

[Jack90210]

Correct me if I'm wrong, but once we move from the OE 275/60/18 SL-rated tires to 275/70/18 E-rated tires... that door sticker is irrelevant. I just had my BFG KO2s rotated yesterday and the shop (Discount Tire) went by the door sticker - 40 psi. I'm assuming that's both a habit and policy. I swear, I can run over a quarter and feel the date.

I've put about 130,000 miles on BFGs (third set) and a lot of those miles at 32 psi. But I keep hearing that E-rated tires HAVE to be run at higher pressures. I get that they CAN be run higher... but why do they have to?

Here's why (short version):

Tires aren't built to handle LOAD as much as they are built to handle AIR PRESSURE. LT tire = heavier construction in order to handle higher pressure = less flexing for a given load at a higher inflation pressure, hence more load capacity.

The extra material in the heavier-built LT tire requires a higher inflation pressure in order to resist excessive flexing. When it is run at the same pressure as its P-rated equivalent, the tire experiences a substantial energy input in the form of said flexing, and it can much more easily heat up (which means tire failure).

LT rated tires can handle much more (than an equivalent-sized P-rated tire), but ONLY when they are inflated to the much higher operating pressures that they were designed for.

This is worth a read: https://www.toyotires.com/media/bszlobyw/tsd-12-011_replacing_tires_on_light_trucks.pdf

 

[Jack90210]

.... Why is the load rating for the E-rated tire 176 lbs. lower than the SL-rated tire? ....

Because the load capacity of a P-rated tire is de-rated by 10% when used on a light truck or SUV, as mandated by (IIRC) DOT.

The calculator takes that into consideration when factoring the equivalent load of an LT tire.

 

[Mike NXP]

I played with that site/calculator... came away more confused. I'm going to assume I did something wrong here or all I thought I knew about tires was wrong. School me.
Why is the load rating for the E-rated tire 176 lbs. lower than the SL-rated tire? And obviously related to the first question, why does an E-rated tire need MORE psi than an SL-rated tire.


View attachment 3713129

Your using the tool right but overthinking it slightly. That tool is using load ratings based on size to spit out a pressure to allow the same GVWR as your stock tire and is just a good reference point rather than opinion

An E-rated tire needs more pressure than an SL to achieve to same load capacity so if you run it at 32 PSI you have far less load capacity than stock SL tire

I do agree it's sort of weird that they show a slightly lower capacity rating when converting to E rated and I've got no explanation for that BUT the key take away is you know to achieve a similar load capacity as SL but with an E rated you need at least 37 PSI


Switching to E-rated tires allows folks to run lower pressures ( air down off road ) while still maintain a decent load capacity. It also helps folks who are just running a lot of weight and may exceed the GVWR when running the SL tire ( fully loaded, pulling trailers, etc. )

 

[Manhattan]

Okay, that does help. Thanks @Mike NXP.

I recently bought a 2020 4Runner and immediately bought a set of BFG KO2s (clearly I'm a fan) in the stock size - 265/70/17... but C-rated. Now, the 100 rides like absolute &%#@. I didn't mind those E-rated bricks for 160,000 miles. 10 miles on the C-rated tires and I vowed to never buy an E-rated tire again.