Owners manuel states that my truck GVWR is 14500 with 18" wheels which I have. GVWR is 15000 with 17" wheels . Go Figure!!!!
David

 

I think the 18" wheels have a bigger circumferance therefore reducing the effective gear ratio. That's what's dropping your rating.

 

Simpull fizicks.

 

That's GCWR. GVWR is the truck's weight rating, not truck + trailer.

Two other points about 18" wheel option. They are heavier which affects performance and less rubber = lower tire weight limits.

 

It reminds me of when 17" truck tires 1st came out only in "P" serries on the Expeditions.

People got the 17" and had no load capacity......wait, tire builders will catch up to the 18". There are now Loading ranges "F" and "G" in 16's available.

But if it is a low profile 18" tire(under 70 series), you will never get a high load range because the tire has no room to give before the wheel is hit.

 

the new superdutys can be ordered with 18 wheels, they must have a pretty substantial tire?