Tire question

[wincrasher]

My new Outback 298RET came with tires stamped load range d.

After hours on the highway on a 65 degree day, they were fairly cool to the touch. Maybe they were 80 degrees. (guess).

My trailer dry weight is around 7500lbs with a stated load capacity of 1500 lbs.

Are these tires maxed out? I don't really know how the load capacity is determined - if it's tires, axles, bearings or the frame structure - or some complicated calculation considering all three?

[SteveC7010]

This tire chart shows the load ratings for ST tires:


Presuming that you run your tires at 50 psi and they are ST225/75R15's the load rating is about 2150# per tire. If you run them at higher pressures, the load ratings increase per the chart.

Your trailer is 9,000# GVWR and the tires can do up to 2,540 each which adds up to a greater capacity than your trailer GVWR. Obviously tire pressure matters.

Trailer GVWR's are determined by the weakest part, be it axles, wheels, tires, or frames. Axles typically are rated above the rating of the trailer. My last trailer had two 3,500# capacity axles and was rated at GVWR of 5,500#. Axle ratings include brakes, springs, and bearings. It is a single package.

Wheels have load ratings that are usually higher than tires. The info is usually stamped on the wheel somewhere.

We've talked about tires, so the frame is the last part and that is usually proprietary info. Manufacturers combine all that stuff and come up with a GVWR that is likely very conservative compared to the individual components.

So, if you run your tires at proper inflation for the GVWR, you still have reserve capacity: 2,540# x 4 tires = 10,160# capacity of the tires. Given the fact that they did not heat up, you are probably doing very well.