Probably no change
Maybe, but probably not. Your GVRW (maximum allowable gross vehicle weight) should be the smallest weight bearing value among your single axle [presumably a Dura-Torque type, hence no springs], wheels and tires. You just upgraded the single axle from 3200 pounds to 6000 pounds, so by far it's not the smallest value anymore (if it ever was). Wheel ratings are difficult to determine, but assume at a minimum they exceed the largest recommend tire that mounts to the wheel.
Your tires should have their weight rating molded into the side walls, so find it on one tire, multiply by 2 for both tires, and that's you new [maybe higher, but probably not] GRVW. If you installed heavier rated tires on the same wheels, then your GVRW will likely increase by the difference between your old and new tire ratings (assuming the wheels are sized for the new tires and vice versa). GVRW would vary with tire pressure in my example, as I assume the tires have the smallest weight bearing value of the three suspension components and the wheels are rated to exceed the largest recommend tire size and rating that fits on them.
Fred Coldwell, WBCCI #1510, AIR #2675
Denver, Colorado - WBCCI Unit 24
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