So I did search this site and other sites and Google but you also get hundreds of different answers. I recently purchased Falken Rubitreks and want to know what others are running in their LT tires. These are E rated 275/70/18. Can’t go by door jamb because it’s not a stock tire anymore. I won’t be hauling or towing anything for now. 80 is the cold max pressure. I may try 50 for now and drop down a couple pounds at a time to see what feels good. So far I like the way they ride and handle. There’s less sidewall flex and they handle the usual bumps a little better. Thanks in advance.

 

That’s a whole lot of pressure for a light truck. Sometimes manufacturers will provide a weight capacity by inflation psi chart. I’d do the chalk test to make sure you wear them evenly.

in my previous F250 I’d run 42 up front and 35 out back when unloaded. That gave me the best wear and ride.

 

With E-rated tires, you will want them MUCH lower when you are driving around empty. 45-50 is probably fine, just make sure they are wearing evenly. Then when towing/hauling, pump-em up as high as you want, 60-70-80 or max sidewall pressure.

 

So I tried 50 pounds and that was a little too firm. I lowered the pressure to 45 for the ride home. Not much difference. I’ll try the chalk test one day. I may even drop to 40. Keeping an eye on wear. Thanks

 

80 PSI is just the MAX pressure to be used in the tire, not the recommended pressure.

Do the chalk test. I put Load Range E tires on nearly a year ago and 40 psi is what I run on the highway. If I'll be driving on dirt for a long time that is dropped to 30 psi.

 

Well they should be a little more firm than the previous tires at any pressure.

 

i understand all that. Many more plys and stiffer sidewall.

 

While LT tires have a stiffer sidewall the door posted tire pressure is the recommended pressure for tires on the vehicle. Ya, I know the tires your running have a sidewall “max” psi of 80 psi but both ride snd performance would be unsatisfactory if you ran at that pressure. As I do tow a 7500 lb travel trailer severa thousand miles a year I too have LT tires on now. Even when pulling the trailer I run about 50 psi max. When nit running I’m using at or near the door posted recommendations. I run 38-40 psi and get both a decent ride as well as handling.
good luck.

 

It is of my opinion that the door sticker is a "general starting" point on tire pressure. The factory wants a better ride than it does wear quality. Different tires, brands, type, etc will require different pressures to wear even. Load will require different pressures. The best way IMO is the chalk test or just pay close attention to the wear pattern. I have found 37 - 38 psi is what works best for the Cooper's I have installed. My last set were worn fairly evenly across the tread pattern with only 1/32" difference across the 11 or so inches.

It is also of my opinion unless you live or travel on unimproved rock roads a lot, E load rated LT tires are a waste and unnecessary on a half ton truck. XL rated tires are more than enough, even when towing a behemoth TT. One XL tire has more load capacity than any half ton truck has. People around these parts jack their trucks up to the sky, put big a$$ tires on and never leave the pavement. Must be making up for some other small part..........

 

The proper way to do it is:
1. Use the load index chart for your factory tires at the recommended door jamb pressure to determine the weight carrying ability of the tire at that pressure.
2. Use the load index chart for your new tires and scan across until you find a weight carrying number that is above your factory tire number that was determined in step #1. Look at what PSI is needed for that weight.
3. You have now found your recommended minimum tire pressure for the new tires. Adjust between that number and the max on the sidewall based on comfort and the load you want to carry.


Example:
Using a factory standard load range tire with an index of 100 and a factory door jamb of 35 PSI....gives 1718 as the minimum recommended weight rating for that tire.
Moving to load range E tires, I have highlighted the first instance of a weight rating above 1718 for each load index and you can then see the pressure required to meet it.
In my example, if your new tires are load index 118, you would continue to use 35 PSI as your minimum.
In my example, if your new tires are load index 102, you would use 75 PSI as your minimum!
**don't use my factory numbers, you need to use your original tire's load index...I randomly chose load index 100 for this example!

 

I used to run 70 towing and 45 when not towing in my Tundra towing a 9K 5er. I just bought my 2018 F-150 with the 7050 load, 20 inch wheels and Tow Max package. I was told Ford is required by law to provide a tire capable of handling the maximum towing and load capacity. Apparently they chose 4 vendors, one of which is Michelin Defender LTX M/S 275/55R20 Tires with a 2535 capacity rather than the "E" rated tires at a 3750 load capacity. I think I'll make a few runs with the tires that are on the truck and then decide whether the 10 ply tires make sense before we make another cross country run.

 

. Thanks. You really went out of your way. I believe my new tires are load range 116. I’ll have to double check. Thanks again

 

Well, that's true for everyone. It's incredible what the max load is on some of the truck-sized P-metric tires are even at 44 PSI or 51PSI or whatever the max sidewall pressure is. Still a pretty squirmy ride when at max load.