Is Your Extra Heavy Class C Too Much For Your Tires?

pianotuna wrote:
Hi Phil,

From a tire tech site:" For example, a LT235/85R16 Load Range E tire is rated to carry 3,042 pounds when inflated to 80 psi and used in a single application, but only 2,778 pounds when used in a dual tire application at the same inflation pressure.

This reduction in rated load capacity results in slightly larger tires being specified for the application that can better withstand the additional stresses experienced when a single tire goes flat and the three properly inflated remaining tires are required to temporarily carry the load at reduced speeds to remove the vehicle from immediate danger."

Hmmm ... I agree with the concept of duallies having a secondary function in addition to raw weight carrying capacity. That secondary function - that to me is very important - is to provide tire redundancy for safety in case one tire of a dually set should fail. However, using tricky specification manipulations - without so stating the purpose - to indirectly keep us consumers "safe" is doing us a disservice - IMHO.

I've always envied dually pickup owners because - unlike dually tired motorhomes - their trucks are rarely ever loaded anywhere near their max rear tire carrying capacities, so having four tires in the rear truly does provide outstanding backup in case one (or even two - one on each side) should fail because most of the time the one tire remaining on the one (or each) side can still carry the truck for many miles, if not indefinitely.

I've actually had that experience with our Class C. I drove several miles with one rear tire flat until I reached a small town with a tire repair shop open. Of course the Load Range E tire on the one side was way overloaded, so the motorhome felt bouncy and unstable in the rear. BTW, that overloaded Michelin tire went on to perform flawlessly for several years after that. The failed Michelin tire went flat due to failure of the plain old everyday rubber valve stem that came stock on the E450, so I was able to continue using that tire, too ... after replacement of it's valve stem (all are metal ones now).

Of course the best in the heavy rear of a motorhome would be for each tire to have a "true" load carrying capacity equal to at least one-half of the weight being carried in the rear. That would make our dually Class C motorhomes have about the rear tire redundancy safety and reliability that dually pickups have when used as a daily driver.

Remember while looking at tires for more capacity, that rims have max pressure rating . My E450 have 80 psi max pressure rating.Raising the tire pressure rating should never exceed the rim rating

beachcomber_1 wrote:
Remember while looking at tires for more capacity, that rims have max pressure rating . My E450 have 80 psi max pressure rating.Raising the tire pressure rating should never exceed the rim rating

The Nexen Roadian CT8 HL tire with a 3195 pound rating for $134.91 has a max tire pressure of 83 psi, just 3 pounds over the rating of the E450 steel wheel. I would think that is within the margin of safety.

The General Grabber HD for $190.99 has a 90 psi max which is uncomfortable.

So Ron ... I wonder how the Roadian tire gets it's 3195 pound rating with only 83 lbs. of pressure? Maybe super stiff/thick material in the sidewalls that support the weight instead of relying on air pressure in a chamber supporting the weight?

Something doesn't smell right here. :h

(Where is a tire design engineer when you need him.)

pnichols wrote:
So Ron ... I wonder how the Roadian tire gets it's 3195 pound rating with only 83 lbs. of pressure? Maybe super stiff/thick material in the sidewalls that support the weight instead of relying on air pressure in a chamber supporting the weight?

Something doesn't smell right here. :h

(Where is a tire design engineer when you need him.)

I agree, it doesn't seem to add up.

I found the same exact tires sold by Tire Rack as well as Tire America. The 3195 pound rating and 83 psi max matched. So it's not a typo.