BACK2GAS

Hey guys recently upgraded to some Cooper AT3 XLT load range E tires 265/ 20 r20. I regularly have about 1000 pounds in the bed and I'm wondering what you guys run for air pressure for those running load range E tires.

Looking for a little insight on what to run when loaded, towing, and unloaded. They max out at 80 PSI, but I'm wondering if there's a rule of thumb to follow when hauling or running unloaded. I doubt that I'll run them too low, but I also don't want to run them unnecessarily hard either, especially when it raining.

Thanks

jeffinthebag

I keep 50 to 55 in my LT E's. Air up to 80 only if needed.

smokeywren

No such thing as a 20 aspect ratio. Cooper makes a 265-50R20, but it is P-Series instead of LT. They make LT tires up to 18" diameter, but I cannot find a Cooper LT 20" tire on their website.. Are you sure your tires are LT265 and not P265? http://us.coopertire.com/tires/discoverer-at3-4s.aspx

There's no "rule of thumb, but the proper PSI in your tires is indicated by the Tire and Rim Assn. (TRA) load/inflation tables.

The TRA load inflation tables are needed to tie down the info you asked for. They publish a new table each year, but only members get a copy, and membership is very expensive. Most tire manufacturers refuse to publish the TRA load inflation tables because of fear that idiot customers would misunderstand the tables, then sue the tire manufacturer for a bunch of money. So most of the tire manufacturers tell you to go by the PSI for your tires that is included in the Federal Certification label in the driver's doorframe.The only place I can find a current load/inflation table for light truck tires is on the Toyo Tires website, but they hide it so most web surfers cannot find it. It's at https://www.toyotires.com/media/2125/application_of_load_inflation_tables_20170203.pdf

Scroll down to page 24 and you'll find the only LT265 R20" tire size Yoyo makes is LT265/60R20E. So I'll assume your new tires are that size.

Here's the load/inflation table for size LT265/60R20E mounted on single wheels (SRW):

PSI . Max load (lbs)
----- . -------------
35 ... 1825
40 ... 2000
45 … 2175
50 ... 2335
55 … 2500
60 … 2660
65 … 2835
70 … 2960
75 … 3110
80 … 3195

So load the F-150 to whatever weight you expect to be using, then apply the load/inflation table. If you want hauling and unloaded PSI, then you'll need at least two scale tickets. Divide the weight on each axle by two to get the load on each tire.

Don't overload your F-150 over the GAWR of each axle. If your tire size is LT 265/60R20, your rGAWR and fGAWR are probably less than 4,000 pounds, so you'd never need more than 40 PSI in the either front or rear tires. My fGAWR is only 3,300 so I'd need only 35 PSI in those tires. My rGAWR is 3,800 so I'd need 40 PSI. Overinflation will result in prematurely wearing out the center treads of the tires and reduce braking effectiveness.

BACK2GAS

Thanks didn't see that typo. Yes you're correct they're 265/60 r20.

Jrizman

Copper M&S with studs on 18 wheel.
I'm running around at 40-42 psi. Tow a small sled trailer up icy snowy roads on the weekend. Seems to be a good pressure for my truck. Might run a few more psi on road trips all loaded up.
if I were hauling a lot of truck weight or bigger trailer, I would add more air.
80 is not reasonable in a 150 in my opinion, see how it rides for yourself sometime.

Watch tire wear and contact patch on the pavement and see how it rides at different pressures. Then pick what works for you. E tires have nice stiff sidewalls!

kbroderick

IMO, the best answer is going to come from doing a chalk test (while keeping the load rating-vs-pressure table in mind), but I've found that 43 front / 41 rear (unloaded) works well for me. I do have a heavy front bumper assembly, so my front axle is often close to the 3600-pound GAWR, and I don't often have a whole lot of weight in the back.

I thought I'd need to add more air when I was towing, but it seemed to perform fine with those pressures driving cross-country with a 7k-pound trailer last summer (and I did keep an eye on the cold vs hot pressures as well as tire temps measured with an infrared thermometer; nothing seemed out of the ordinary with either data point).

BACK2GAS

Thanks I'll try those pressures and see how they work for me.

Run-n-gun

jeffinthebag

On my f150 that came stock with "E's". The TPMS light lights up at 40 lbs of pressure.

marshallr

Since an E rated tire is stiffer you need LESS air pressure to carry the same load as P series tires. You'll just have to experiment. With P series tires I tend to keep 38-40 PSI in my tires for general use and 44 PSI (max) when carrying heavy loads or towing.

That is about right for a 3/4 or 1 ton truck, you're needlessly beating yourself up doing that. Way too much for a 1/2 ton. Generally you'll get the best ride,and still plenty of stiffness with about the same, or slightly less air pressure than recommended for P series tires. The wheels on a 1/2 ton aren't designed to hold together at 80 PSI. Look at Smokywren's data. An E rated tire at 45 PSI is rated for way more weight than a 1/2 ton truck can carry.