Tire Ratings

[JimK-NY]

There is no doubt about it. Truck campers are heavy and most of us are probably close to the load capacity of our trucks. When it comes to load capacity, the limiting factor is often the tires. I know that is my case and my rear tires are carrying close to the rating. To significantly increase my tire load capacity, I need to spend about $3000 for an upgrade to 19.5 wheels and tires.

Ideally I am sure we would all like to have tires rated at more than twice the load we are going to carry. But what do the ratings really mean? Is a tire safe at the rated capacity? It seems to me that a rating should mean the tire is safe at that load. It should be safe as the tire is used and wears at least halfway. It seems there should be some safety margin built into to the official rating.

I do understand that a rating will never compensate for a damaged tire, or for an underinflated tire, or for an old tire that is starting to dry rot. I also understand that a tire can fail even under the best of circumstances. I have had defective tires from Firestone many years ago.

[Old-Biscuit]

I have 17" wheels and tow 14K 5th wheel
I run Michelin LTX AT2 rated at 3195# @ 80 psi
They have a speed rating of 'R'---106 mph

For 7 yrs FT travel I ran rear tires at MAX ---80 psi because when 5vr hooked up I was right at rear tire MAX Load Rating (6390#...SRW ---just under RAWR)

Drove mainly 62 mph or less cause we traveled back-roads but have run them at 70 mph on Interstates. And would have no concerns about tires doing so over long periods.
The tires have a MAX Load At MAX PSI Rating which means they are safe and capable of dong so.
I get at minimum 60K mileage and then get new tires......not because they wear worn out/down to thread wear bars but because I am 'anal' about tires when towing FT

[Grit_dog]

JimK-NY wrote:
I found the speed rating for my tires, rating Q, 99 mph. But does that mean at full load? Does that mean at full load but only in the winter?

Don't overthink it. Load capacity is for normal conditions. If that's summertime going 80 down the highway or 30 below doing 30 mph.

[Grit_dog]

JimK-NY wrote:
Unfortunately, there is no up two sizes available. My truck came with 17" rims and the max load available seems to be 3200 pounds. Even so, what about someone else who upgraded and is still at the load capacity for the larger tires?

Is there a 55 or 60 mph limit on the rating? I can find load ratings but no speed ratings for my tire size.

295 70-17 size Toyo MTs are rated at 39xx lbs.
not a lot of options in 17s though for whatever reason. Strange considering they were the go to size for about 15 years and still are coming off the line everyday on HD pickups.
If you have a 8x6.5 bolt pattern there are a lot of reasonable priced options with OE Ram takeoff wheels in 18 and 20" sizes and more tire options with those.

[Grit_dog]

Having double the actual load for rated capacity seems, how shall I put it, completely overkill, and virtually impossible to accomplish on a srw truck with 4tons over the rear axle.
You should not expect to have issues loading good tires up to or even a bit over their capacity.

[JimK-NY]

I found the speed rating for my tires, rating Q, 99 mph. But does that mean at full load? Does that mean at full load but only in the winter?

[Kayteg1]

What is killing the tires is not the overload, as they can take 5 times the rated weight for rolling, but the heat.
Heavy loaded tire flex a lot and that generate heat. Faster you drive - more heat is generated. When temperature gets at high level, the rubbers will deteriorate and then POOF.
So observe your tire temperature on rest stops. Touch by hand is adequate. If you feel the tires too hot to touch- you better investigate and slow down.

[JimK-NY]

Unfortunately, there is no up two sizes available. My truck came with 17" rims and the max load available seems to be 3200 pounds. Even so, what about someone else who upgraded and is still at the load capacity for the larger tires?

Is there a 55 or 60 mph limit on the rating? I can find load ratings but no speed ratings for my tire size.

[kohldad]

Yes, an LT tire is safe at rated capacity if you are maintaining a reasonable speed around 60mph. Cant' find it now, but from previous research, I believe they are tested at 55mph.

If you go up two sizes, usually you can gain a couple hundred pounds of additional tire capacity. You would need to verify the rims are capable of the higher capacity as well.