CAT Scale


As we made our way on our first excursion with the Castaway, we decided to make a stop at KAL Tire to check our air pressure and then over to a local CAT Scale to weigh our coach.

Perhaps we should have done this the other way around, weigh the coach first and then adjust the air pressure. I have to tell you though, that I am finding the advice on tires and tire pressure to be quite divergent.

Newmar, the manufacturer of our coach, has their own weights and recommended tire pressures which they affix to a sticker near the captain’s chair.


The steer axle is 15,400 pounds and the drive axle is 30,000 pounds. They recommend a cold inflation pressure of 120 psi for the front, 90 psi for the duallys and 85 psi for the rear,

Of course, those weights represent the Gross Axle Weight Rating, or the maximum distributed weight, the axles of the coach can support. We do not intend to max out the load on the Castaway.

Our dealer had inflated our tires just prior to the delivery. We were told to keep them at 110 psi for the front and 90 psi for the tag.

Taking them to KAL Tire, they recommended 120 psi all around.

And the tables at Michelin Tire have a different set of pressures yet again based on how much the coach weighs.

In our case we have a steer axle of 14,160 pounds or roughly 7,000 pounds of load per axle end. Michelin recommends 105 psi for the front tires.

As our drive axle weight is combined, it is not possible to get a direct load from the Michelin site. That said, they do recommend 80 psi for the duallys and for the rear.

Very confusing.

We drove down to our campsite in the Thousand Islands with the tire pressure as set by KAL tires. The Castaway rode very well. That said, I am going to place a call directly into Newmar. We’ll see if we get any further clarification on how much air is too much, or too little.

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