Making sense of Tire Load Rating and Load Index?

[21F150_208]

I am going to be running a payload of 60% of max in the Summer and am advised to get a tire with a D or E load rating. Meanwhile, I'm looking at tires with a load index of 114 or 116.

Why not just use one measurement? Load Index appears to be more widely used in tire specs.

It seems like D load rated tires are 8 ply, and E load rated tires are 10 ply(?) The weight carrying capacity difference between 114 and 116 is 2601 lbs versus 2756 lbs.

Once I get past this load topic I'll look at off-road v road and expected terrain. As long total load carry is less than GVWR beyond ride & gas mileage aren't we good to go?

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[UGADawg96]

The load index in LT (E) tires varies based on PSI. They may be 2400 at 45lbs, but 3400 at 75lbs.

Look here:
https://tirepressure.com/lt285-60r20-tire-pressure

Whereas on passenger tires, the load index is much more constant anywhere between 30 psi and 40psi

 

[PBXL]

As a brand new full size truck owner myself, this is an area of great confusion. I can only share my personal experience so take it for what it is worth.

I swapped my stock tires out for LT tires because I knew I wanted to be towing once in a while. I don't know what LT stands for, but my guess is Light Truck? Anyways, LT so far seems synonymous with E rated tires, which I learned are good for towing. If you choose to go with LT or E rated tires, then the next area of confusion is what PSI to run. Big O tires put 35 PSI cold in my LT tires. This is what is in the drivers door for cold PSI recommendation. This lowered my MPG by 2-3. After reading multiple forums on the internets, I pumped up my tires to 45 PSI. This is the highest PSI I have ever put into any tires, so I was pretty hesitant. I thought my tooth fillings would shake loose while driving. Luckily, this has not been the case and the ride quality is still very good at 45 PSI cold and my MPG went back to normal as well. I also towed a 5000 lb trailer at 45 PSI and everything was great.

 

[21F150_208]

Thank you! I've never considered running a higher PSI.

 

[aika1]

I am going to be running a payload of 60% of max in the Summer and am advised to get a tire with a D or E load rating. Meanwhile, I'm looking at tires with a load index of 114 or 116.

Why not just use one measurement? Load Index appears to be more widely used in tire specs.

It seems like D load rated tires are 8 ply, and E load rated tires are 10 ply(?) The weight carrying capacity difference between 114 and 116 is 2601 lbs versus 2756 lbs.

Once I get past this load topic I'll look at off-road v road and expected terrain. As long total load carry is less than GVWR beyond ride & gas mileage aren't we good to go?

Oh my, this is a big can of worms.
LT tires are "light truck", yes. They come in C, D, and E in the most common designations for passenger trucks, and go higher for trailer tires (F, G, H, etc.). Back in the day it related to a ply rating (c had 6 plies, d had 8 plies, and E had 10 plies). That is no longer the case. Now MOST of those tires have the same number of plies, and the letter designation of E corresponds to a weight rating that roughly equals that of a 10-ply tire. Get it? still 2-3 actual plies, but the tire's weight carrying capacity is equal to an old 10-ply rating from back in the day.
LT tires work differently than P-rated tires (stands for Passenger). P-rated tires are built to hold a weight relatively without regard to PSI. LT-rated tires are built with a varying weight capacity, based on the PSI currently used. so a LT-E is rated for a maximum of ~2700 lbs at say 80PSI. it is NOT rated at 2700LBS at 40PSI. It is rated for significantly less at that 40PSI.
Where that comes in handy is when you want to air up your tires for a large load (heavy trailer or payload), you can, and when you want to air down for a smoother ride (with LT tires, less PSI means a "softer" carcass that's more forgiving), you can do that for ride comfort.
A LT-C will ride softer and smoother than a LT-E tire. LT-E's are common on 3/4 trucks as standard equipment. They are typically NOT on 1/2-ton trucks like the F-150's because the weight is low enough on the truck that an LT-E will ride stiffly. I worry about that if/when I lift my truck and may have to go to an LT-E for size.
Oh! and LT tires typically weigh more for the size tire when compared to P-rated tires, have more tread depth, and many do not come with a treadlife warranty (50k miles warranty, etc.).

I hope this gets you started!

 

[DBL R]

For those of us who tow only a few times a year, a p-rated tire with adequate max load rating “should” work?

arbitrary numbers: a truck with payload of 1,500 lbs and a trailer weighing 6,000lbs with p rated tires that have a 2,600 lb load rating. Approx 400 lbs for occupants, 10% hitch weight so approx 600 lbs hitch. Those would come out to approx 1,000 lbs total. So within payload and we’ll within the 2,600lb load rating of the tires. So with these arbitrary numbers one could easily tow without requiring LT tires? Is my math right or am I missing something here?

 

[Roscopcoletrain]

with my previous trucks, I used to go with a E/LT tire. When I got my Sierra, I went with an XL (Xtra Load) tire. Sorta in between a P and a LT. They worked good, and I'd say for part time towers, a good choice.

 

[21F150_208]

Oh my, this is a big can of worms.
LT tires are "light truck", yes. They come in C, D, and E in the most common designations for passenger trucks, and go higher for trailer tires (F, G, H, etc.). Back in the day it related to a ply rating (c had 6 plies, d had 8 plies, and E had 10 plies). That is no longer the case. Now MOST of those tires have the same number of plies, and the letter designation of E corresponds to a weight rating that roughly equals that of a 10-ply tire. Get it? still 2-3 actual plies, but the tire's weight carrying capacity is equal to an old 10-ply rating from back in the day.

Oh! and LT tires typically weigh more for the size tire when compared to P-rated tires, have more tread depth, and many do not come with a treadlife warranty (50k miles warranty, etc.).

I hope this gets you started!

I never knew that one should inflate E rated tires to 75 or 80 psi until I started down this path. I thought the yellow sticker in the door jam was to be followed at all times.

I ended up getting E rated tires that were 48 lb each - most seemed to be in the 60+ lbs range. I'm making up a bit for the PowerBoost payload loss with lighter tires.

Like everything else, I wanted a different look that what I bought, with tires sold by my tire shop, that were e-rated, at a great price. It was a pick any three of the four kind of deal. I've owned the brand I bought for decades and gotten 80,000 miles out of a prior set, so I'm happy. Thanks for a very helpful post.

 

[aika1]

I never knew that one should inflate E rated tires to 75 or 80 psi until I started down this path. I thought the yellow sticker in the door jam was to be followed at all times.

I ended up getting E rated tires that were 48 lb each - most seemed to be in the 60+ lbs range. I'm making up a bit for the PowerBoost payload loss with lighter tires.

Like everything else, I wanted a different look that what I bought, with tires sold by my tire shop, that were e-rated, at a great price. It was a pick any three of the four kind of deal. I've owned the brand I bought for decades and gotten 80,000 miles out of a prior set, so I'm happy. Thanks for a very helpful post.

The sticker in the door is for tires that came on your vehicle, specifically the TYPE of tire. So if your rig came with P-rated tires, follow that sticker as long as you stay with P-rated tires of the same size. Going to an LT? that sticker goes out the window and trial-and-error becomes your friend. Some folks will air up a few PSI for longer trips and better mileage (run more on the middle of the tire) or for heavy loads that will distort the tire. Lower PSI for comfort...

 

[wipakrat]

I went with Goodyear Wrangler Duratrac RT - Kevlar, Snow/Ice rated. LT275/55R20 Load Range E,
3085 Load at 80psi, I prefer to run mine at 60psi-rating at 3015, never failed me yet, features 18/32 tread depth, at 1 years and 15,000 miles still about 15/32, excellent wear. This combo is steady with any trailer I have pulled and still a smooth ride.

 

[Jerome10]

There are load and inflation tables out there that you really have to check. The door jamb sticker, as someone pointed out above, is only for the OEM tires that came on the truck. If you change the tire type, load index, any of that sorta thing you have to check your load tables and adjust your PSI accordingly.

There are P-Metric (these have something like P225/55-17), ISO-Metric (no "P"... so 225/55-17), LT (I think these are usually LT225/55-17), and even "flotation" tires that have some weird way of measuring them.

P-Metric and Euro-Metric are similar, as are standard and XL load tires. But again... you have to check the load and inflation tables as they do vary slightly. XL tires can carry more load at higher PSI than SL tires. Then getting into LT tires you have different load ranges (like "E"), as you mentioned.

My understanding is that you do not want to go below the load rating of the factory tires. Whatever those load ratings are, at the given PSI, you want any replacement tires to be able carry at least that much weight. With that said, especially on a pickup, if you're running unloaded all the time you PROBABLY can safely get away with running lower load ratings, but you have to keep in mind you will have a lower load capacity.

Oh, and any P-Metric or ISO-Metric tire used on a light truck, you have to de-rate the load capacity by dividing by 1.1.

https://www.toyotires.com/media/pxcjubjs/application_of_load_inflation_tables_20200723.pdf This guide from Toyo should prove helpful.

Just as an example, my truck has the 275/65-18 116T (load index 116, speed rating of "T") Goodyears Wrangler Territory AT on them from Ford. This is an ISO-Metric tire since there is no "P" at the front. This is a SL (standard load) tire since they do not have XL on them (extra or reinforced load). Sticker inflation pressure is 35PSI.

On that Toyo link, page 34 (which is ISO-Metric, Standard Load), load index 116 at 35PSI can carry 2668 lbs per tire. Keep in mind that 10% factor for light trucks, so derating by 1.1 for an F150 means that this tire, with this load index, at this PSI is rated for 2425lbs on a F150. But basically any tire you replace the OEM tire with (without adjusting) must be rated for 2668lbs or more at whatever PSI you run your tires at.

Just as an example, lets say I used the same 275/65-18 116T tire size and load index.... except I get an "XL" load tire. Using that Toyo chart, load index 116 and 35 PSI from my sticker, this tire would only have a weight rating of 2370 (Page 37). Clearly below the OEM capacity of 2668. Therefore if I used this tire, checking the tables, I'd have to either 1) increase the PSI to 41 on the XL tire (2679 lbs) or 2) I could use the 35PSI sticker but I'd have to get a 121 index XL tire (2745lbs).

You can use this information for the LT tires as well.

The only thing I'll say is that I'm not experienced in towing. My logic says that if your tires can carry what the OEM ratings are, then you can tow whatever the OEM tow and payload weights allow. So like my Powerboost is rated to tow up to 11,000lbs with my standard tow package (12,300 if I had Max Tow), and my payload is like 1670lbs. So as long as I'm at 35PSI on my tires, the tow weight is below 11,000lbs and my payload is under 1670lbs I should be fine.

Butttt... some people I hear swear that towing with LT tires is better, or the tires last longer or something. Will have to leave that to the towing experts.... Ride comfort I think is also affected.

Sorry this is long but I hope it helps folks shopping.

EDIT: You should also add a supplemental Tire & Loading sticker to your door jamb if you make significant changes to the tire type and inflation pressures. I THINK you can also usually reprogram the TPMS system to adjust for higher or lower pressures before it alerts.

 

[wipakrat]

Personal experience with many trailers:
P rated is for Passenger
LT rated is for Light Truck or as I say Trailer rated, No sidewall roll at 60 psi.
My Wranglers tow exceptional and when just the truck, I have a better ride than my wife's car.
Just my opinion

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