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.

[JimK-NY]

Thanks for all the responses. Unless I missed something it seems we have lots of opinions, but not much in the way of facts. Opinions seem to vary widely. Some view the load rating as the "bleeding edge". On the other hand, one poster believes a tire can carry 5 times the load rating providing it does not overheat. Most of us seem to believe, as I do, that the loading rating is indeed a safe load under typical driving conditions including highway speed and hot weather.

I think I will try some additional internet research.

[Bedlam]

Agreed with Kayteg. That was the point I was trying to make about dropping my TC on my unrated trailer and moving it around.

You can find pictures on this forum of failed rims where the center separated from the outside rim. I have seen cast rims fail too - the spokes will start to get hairline cracks until one spoke gives and then the rest snap.

[SugarHillCTD]

I agree with LamboDesigns.

On the truck in my signature I am running the stock steel wheels with Nitto Dura Grapplers that are rated at 3970#.

While GM will NOT reveal the specific load capacity of those wheels (their very slow to respond email indicated that the wheel ratings are the same as the OEM tires, so it is a CYA position) I have yet to find any info on OEM steel wheel failure.

I am very confident driving our heavy TC on those wheels/tires and while we avoid highways as much as possible, when we do go on them, my speed is right around 60 mph.

[Kayteg1]

How often farm truck run at 70 mph for several hours?

[LamboDesigns]

Just a question and not saying to disregard the wheel rating but has anyone every heard of a wheel failure (at least a modern OEM wheel) due to overload? I did a little looking and all I found were results of damage due to lug failure, tire failure, or collision with immovable objects where any wheel would have failed. I'm certainly not worried about mine as I'm under their rating and knowing what abuse I put wheels (and not modern ones either) through on the farm as a kid. The weight police would have strung me up for a few of the loads I brought home from the gravel pit, feed mill, hay field, etc. at the ripe old age of 16 or 17 on a 67 Ford F250. That truck was run hard and put up wet until we thought it was about dead so we sold it to a neighbor kid that put another 100k on it before it really went to pasture.

[Kayteg1]

JimK-NY wrote:


I live on Long Island, NY. I doubt there is a grain elevator within a 1000 miles.

What did I win?

[JimK-NY]

S Davis wrote:
One thing I would keep in mind if you at max on your tires/wheels, your load is not the same on both sides and even though you could be fine with the load on the rear axle one side could be carrying more weight than the other and be over. So if you are close it is a good idea to weigh each rear tire to see where you are.

I think I am pretty well balanced except for the generator. The fridge is one of the heaviest items but it is balanced by the two big AGM batteries on the other side of the camper.

[JimK-NY]

realter wrote:
Have you found a place to weigh your Igloo? Almost any farmers grain elevator will let you roll over their scale, for free, as long as it's not harvest.

I live on Long Island, NY. I doubt there is a grain elevator within a 1000 miles.

[S_Davis]

One thing I would keep in mind if you at max on your tires/wheels, your load is not the same on both sides and even though you could be fine with the load on the rear axle one side could be carrying more weight than the other and be over. So if you are close it is a good idea to weigh each rear tire to see where you are.

[realter]

Have you found a place to weigh your Igloo? Almost any farmers grain elevator will let you roll over their scale, for free, as long as it's not harvest.

[Bedlam]

I prefer to not exceed the ratings on the tires and rims. This means I need some reserve to allow variation in what I pack instead of sitting on the bleeding edge. I would have a little different view if I loaded my truck camper on my 3500 lb rated trailer to move across the property at low speed verses dragging it down road at highway speeds.

[JimK-NY]

Bedlam wrote:
.....If you are close to your tire limits, will you be weighing your load each time you go out or not varying what you will take with you? .......

This is the sort of thinking I would like to resolve. If you have a load which keeps each of your tires a hundred pounds or so under the rating, then I guess you are in a safe weight range. If you up the load and go a 100 pounds over, I would think that would have virtually no change in the safety of your tires. Wear, speed, temperature, road material and road condition would have much, much bigger effects. At least that is my guess. I know I am close to the load rating for my rear tires. To my thinking, nothing changes if I am a bit under the rating or a bit above.

[Bedlam]

I was close to the limits of my 275/70R18 LRE Michelin tires (7500 lbs on the rear axle). I did not want to worry what I carried and how on the truck and attached trailer to make sure I stayed under those limits which is why I went to 245/70R19.5 LRH tires. If you are close to your tire limits, will you be weighing your load each time you go out or not varying what you will take with you? For us, each trip is loaded differently based on destination and duration and it was not worth it play load master to keep everything balanced and within specifications every time. I ended up rarely exceeding 8000 lbs (that 4-tons Grit dog posted) on the rear axle and the 19.5" rims gave me 9000 lbs of capacity which gave me plenty of reserve capacity for any changes I wanted to make.

[jimh406]

Tire ratings relative to each other. If you update to tires that have a 4500 lb capacity, and currently have 3670 lb capacity, you've increased your buffer. Do you need it? You have to answer that question. Blowouts aren't fun and can cause thousands of damage even if you or others aren't hurt.

When I drove my SRW with my current TC, I went for 19.5 Gs because I liked having the extra margin of safety. Probably was overkill, but that's ok with me. I couldn't get by with a DRW at the time since the SRW was my daily driver and even it just barely fit where I needed to park at work.

[Kayteg1]

FYI, most of the motorhomes put full rated load on the tires and sit on it every single day. Some even have more than rated load straight from the factory.