Size Tires for Towing a 5th wheel

[pmarker]

I am working on ordering a new RAM 3500 with Diesel engine. The 5th wheel trailer I am pulling will be about 15K lbs with cargo and a hitch weight of 2600 lbs. Should I go with 18' or 20" tires based on this load?

 

[theblet]

Are you talking about the rims? I don’t think it matters as long as the tires can handle the payload.