Can someone explain load ranges to me?!?

[SparkyTX]

Okay, maybe I am just dense...

I have never really been concerned about laod ranges on my tires before, but I also haven't ever tried towing as much as I plan to now.

Anyway, I would expect load ranges are a fixed weight range, i.e. load range D = xxxx lbs to xxxx lbs, load range e xxxx lbs to xxxx lbs. I would expect those ranges to be fixed and held across tire sizes, brands, etc. That would be logical to me.

Reason I ask is that my stock tires (245s) are load range E. They are labelled max of 3032 lbs (or close to that, I don't recall exactly). I was looking at some 285s, but I can't find any over load range D. However, the BFG ATs that are load range D are labelled at max of 3300 or so.

Only thing I can find about load ranges on the net is that they replaced ply ratings, but nothing tells me what the "ranges" mean.

Anyone?

[gardnerteam]

I won't try to explain load range to you, but I will tell you Nitto makes a 305/70/16 Load Range E which is the same diameter as a 285, just a tad bit wider. I have about 10,000 miles on a set and they have been great tires, but do not appear to wear better than anything else. They will probably go 18,000 miles for me. I am going to 245/19.5 next time which is the same diameter as the 285 and 305, but narrower and load range G - 14 ply rating and a lot more load carrying capacity.

[Black Dog]

A bigger size tire will have a higher weight rating for a given load range. This is why a D rated 285 can carry more weight than an E rated 245.

[David Utz]

Think of load range as the amount of air that you can put in the tire. D=50 psi, E=80 psi, etc. As the tire gets larger in size, the area making contact with the ground also increases and allows the larger tire to support more weight. (contact area X pressure = load) If you add more load, the tire will squat increasing the contact area until the pressure X area can support the new weight. Likewise, if you are not running at max load, you should lower the pressure in propotion to the load/max load. This will keep the contact patch the correct size.

[Minn-kota]

I'm not sure if this is completely true, but I believe E rated are 10-ply and D are 8 ply.

I just put on a set of 265/75 Bridgestone REVO's as of an hour ago. Look great!

I need to de-air them a little because, as usual, the ignorant tire guy pumped them up to the sidewall specs (65 psi). Rides like my dad's '60 Chevy single axle grain truck! I'll drop them down to around 55/50 and see how it acts. It sure handles better than the 245's I feel so far.

[huntindog]

OK, I'll take a stab at a simple explanation.
It takes a certain volume of air to support a given weight.
So for a smaller tire to support the same wieght as a large tire, the same amount of air must be forced into it. This results in a higher air pressure. The higher air pressure requires stronger tire construction to contain the increased pressure. That is where plys came into play. Originally the more plys a tire had the stronger it was, and it was assigned a higher rating. As materials and design has improved,a tire with less actual plys can support the same wieght that used to require more plys, so this has become irrealavent. The only reason ply ratings are still used is people are accustomed to them.
There is a small increase in stabilty from using a tire with more sidewall (stiffer) plys. This can be a good thing in trailer towing.
The main thing to remember is; air volume not pressure is what supports the load.

[gardnerteam]

You are correct that some of the new tires with lesser plies will carry more air volume and post higher pressures allowed. One of the problems with them is that to get the full load rating shown, they must be inflated to the max air pressure. Inflating most 4 or 6 or even sometimes 8 ply rated tires to their maximum inflation for maximum load crowns the tire and gives you uneven wear in the center of the tire if you run it for long periods of time at that pressure. The greater number of plies normally indicates a stiffer sidewall and a stronger sidewall less impervious to rock cuts, curb bruses, etc, as well as give you lesser casing roll for better control in many situations. I have ruined all the 6 ply casings I've ever tried, ruined most of the 8 ply casings I've used, but have not had a problem with 10 ply ratings (Load range E). Another note, a 8 or 10 ply rating does not mean the tire is 8 or 10 ply, but that it is rated as such. Most medium duty truck tires are at least load range F or G, and heavy truck tires are beyond that. They also go far more miles per tire at far less cost per mile than light truck tires.

[huntindog]

gardnerteam <You are correct that some of the new tires with lesser plies will carry more air volume and post higher pressures allowed. One of the problems with them is that to get the full load rating shown, they must be inflated to the max air pressure. Inflating most 4 or 6 or even sometimes 8 ply rated tires to their maximum inflation for maximum load crowns the tire and gives you uneven wear in the center of the tire if you run it for long periods of time at that pressure.>

I don't get the point. That statement is true of any tire, not just newer or higher load rated tires.
Are you trying to say that running around empty with 80# in the tires will cause uneven wear? Thats true. On the othe hand even a passenger car tire with 40# will do the same thing IF it is loaded light enough.

[gardnerteam]

In my case on my truck, running empty means a minimum of 9200 lbs plus my weight (260), and my truck almost never runs empty. It tows a lot and I almost always have another 1,000 or greater in the bed. I run between 65 and 80 lbs of air to handle the load, and have worn out 5 sets of tires in 40,000 miles by wearing out the centers. On my 6th set now (Nitto 305 E) which are doing better (will go 16 to 18000), but still have more wear in the center. When I drop pressures, sidewalls bulge too much and driveability is terrible. Wheels are 8" Weld. I need the load range E or better and to get the load rating for the weight I need to run the max pressure usually. Normal scale weights for me with this truck without a trailer are about 13,000 lbs with a load. The best answer for me is to use 245X19.5 load range G (14 ply) which easily carry the weight and give many times the wear. Also a narrower tire which I would rather have. The truck chassis, running gear, and brake and tow system will handle the loads. LT tires will not.

[huntindog]

gardnerteam
Is your truck a dually?
I just checked your tires on Nitto's site.
Their chart shows a max load of 3525 @ 65#.
If this is correct, then you have been puting too much air in the tires. This would explain your poor wear.
If your truck is a dually, then the problem would be even worse.

[gardnerteam]

Not a dually. The only time I put 80 in them was a 1,000 mile +/= to from San Diego to Bend when I had a GCVW of 33,000. Normally run 65 lbs. Again, the Nitto has not worn as badly in the center as the others did. 305 is pretty wide for what I do and I'd prefer the narrower 245x19.5 with a G rating. Tough tire that wears for a long time - one set here on a diesel mechanics truck is approaching 100,000 miles and 6 years.