All about tire load capacity considerations when buying RV tires

In a recent RV forum, a reader asked about getting the right tires with the correct load range and capacity:

I have a 32′ Class A motorhome and am about to pull the trigger on tires. I am very concerned about making sure I get the “right” tires, meaning ones that have the right load range and capacity.

So just today I FINALLY found a place to weigh the MH and here’s what I have:

Front Axle: Actual weight:  4,960    Sticker Info:   6,000
Rear Axle : Actual weight: 10,660   Sticker Info: 11,000
Totals:        Actual weight: 15,620   Sticker Info: 17,000

I was concerned that the 235/85R16-E 10-ply load range of 3,042 was too close to the limit, so instead of that I was thinking of getting a G 14-ply rated tire.

But now that I see the actual weight, should I stick with the E 10-ply range?

Here’s additional info: The RV had 3/4 tank of gas, full tank of clean water, very little in gray water, and me (175 lbs.).

And is this how you figure “Reserve Capacity”?

Tire rating for 235/85R16 Load Range E = 3,042

So is the reserve load range capacity minus actual weight?

Front Capacity: 3,042 x 2 = 6,084
Rear Capacity:  3,042 x 4 = 12,168
Front Axle Weight: 4,960
Rear Axle Weight: 10,660
Front Reserve: 6,084 – 4,960 = 1,124 – I can add this much weight to the front
Rear Reserve: 12,168 – 10,660 = 1,508 — and this much to the back.

Compare to Hercules H-901 Load Range G = 3756 (3415 Dual.. Why?)

Front Capacity: 3,756 x 2 = 7,512
Rear Capacity:  3,415 x 4 = 13,660
Front Reserve:  7,512 – 4,960 = 2,552 *Much better compared to 1,124 lbs.
Rear Reserve: 13,660 – 10,660 = 3,000 *Much better compared to 1,508 lbs.

So, gosh… Now that I have actually put it all down on paper it’s kind of a “duh” moment, but here’s the price difference:

6 – Cooper A/T3 – $1,159 Out the door
6 – Hercules H-901 – $1,532 Out the door
Difference = $373

Worth it?

I offered the following reply:

You didn’t say if the RV was fully loaded with tools, clothes, food and all the other “stuff” you normally travel with. That could affect your tire loading.

Also, it helps if you use the complete tire type/size nomenclature.

I believe you have LT235/85R16 LR-E. The LT is Type. Some readers may have a trailer and have ST-type tires, and there are full metric tires with no leading letters. Each type has different load capabilities and ST are not intended for passenger-carrying vehicles so are not approved for this Class C motorhome.

Second, you failed to consider the correct load capacity in the dual position, as your rear tires are. Tires in dual application ALWAYS have a lower rating than when in single, as one of the pair is almost ALWAYS carrying more than 1/2 the load of the pair.

When you either read the tire sidewall or look at Load/Inflation charts, you will see a different load capability for Single (as in your front tire) or Dual (two tires side to side as in your motorhome’s rear).

The load capacity for an LT235/85R16 LR-E in Dual application is probably 2,778#. Note you should always consult the Load/Inflation tables or what is molded on the sidewall from the tire manufacturer of the tires you are considering, as not all tires have the same load numbers. Some are slightly different for a variety of reasons.

So back to your questions.

“Reserve Capacity” would be the (max tire capability) – (the actual load) on a tire. BUT you cannot simply assume the load on an axle is split 50/50 side-to-side. Some owners find significant variation. So, until you learn the individual tire loads I suggest you assume that one side is carrying 53% of the axle load.

Your heavy side Front could have 53% of 4,960# OR 2,629# (yes always round up), and the Rear could have 53% of 10,660# or 5650#.

The Front Reserve is 3,042# – 2,629# or 413# per tire.

Your Rear would be 1/2 of 5,650# or 2,825#, so the Rear Reserve is 2,778# – 2,825#, or a negative reserve or indication you have a couple tires in overload of 47# per tire. No, that’s not much, but any overload is bad. Also, you may have a larger side-to-side unbalance than 47/53%. Some Class A’s have been found with over 1,500# unbalance.

With this information, it is important that you first confirm the side-to-side load balance.

Side-to-side actual weights are not easy to get, BUT you can go to an FMCA Convention like the one in Redmond, OR, on Aug 13 – 18, where I am presenting tire seminars, or go to an Escapees event. Or check the schedule for RVSEF and check their locations.

Here is a worksheet with info on getting the actual tire load on each tire position, aka “4-Corner weight”.

After confirming the real side-to-side split, you need to re-calculate your reserve load and, if needed, unload or shift the load of stuff in the RV or buy the tires with more load capability. BUT you should never exceed the individual axle ratings GAWR or vehicle rating GVWR shown on your certification label.

Finally, the selection of tire brands. Do the brands you are considering offer the same warranty? Can you find dealers for the brand you are considering in the part of the country you normally travel? Getting a good price on “Mud-Wumper” brand tires may not turn out to be the best plan, if the only location for tires is “Bill-Jo-Bob Cheap tire and Bait Emporium” in West Podunk.

If you get a puncture and need a replacement tire, it could end up costing more than a couple hundred dollars extra if you need a tire rush-shipped in to match your current tires.

Hope this helps.

Roger Marble

Check out my Blog www.RVTireSafety.Net

Read more from Roger Marble on RVtravel.com.

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