How to Select 5th Wheel Trailer Tire Capacity Based on Trailer GVWR  

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When it is time to select new tires for your 5th wheel camper trailer you will want to start with the trailer's gross vehicle weight rating, or GVWR, which is the very most the trailer can weigh. This weight figure should then be divided by the number of tires on the trailer, 4 for a tandem axle trailer, for example.

So, if you had a tandem trailer rated for 8000-lbs GVWR each of the tires should be rated for no less than 2000-lbs. In the most popular trailer wheel/tire size, ST205/75-15 on a 5-on-4-1/2 wheel, we have wheels/tires and tires alone in several weight Load Range ratings: B, 1,480-lbs at 35-psi;
C, 1,820-lbs at 50-psi; and D, 2,150-lbs at 65-psi. In this example you would definitely want to use the Load Range D option which provides a 150-lb safety margin per tire, or 600-lbs for all 4 combined.

The main cause for trailer tire failure, apart from road debris, is excess heat. Excess heat will build up in a tire for any of three causes: incorrect inflation, driving faster than the tire is rated to go, and loading the tire with more weight than it is intended to carry. Any of these, and certainly when more than one condition applies, will cause heat build-up that will lead to tire failure.

You can refer to the two linked article on trailer tires and to the linked page showing our entire range of trailer tires, wheels and pre-mounted combinations. If you select a combination wheel/tire item note that the wheel portion may be rated different than the tire portion; when this is the case the lower-rated part determines overall capacity.

expert reply by: Adam R

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