Something I didn't take into consideration. When I took delivery of the new 20 on Tuesday it just looked and felt taller than my previous 17 F350 dually. I checked the spec sheets before I ordered as height is an issue for towing my fifth wheel. With my 17 F350 my fifth wheel set just a little bit nose high but not enough to be an issue. Before I ordered the new 20 Platinum srw I checked the height specs. The spec sheet shows the srw 350 4X4 longbed crewcab to be .4 shorter than the dual. What I didn't see was this is for the base truck without options. The base tires for both the dual and single are 245/75R/17 which have a 31.5 inch diameter. Tire size does not change with the higher trims on the dual. It does with the singles so instead of 17 inch wheels my Platinum has 20 inch wheels with 275/65R/70 tires with a 34.1 inch diameter, 2 1/2 inches higher than the base. My assumption is this accounts for what appears to be a height difference between the 2 trucks, right?

I'm very hopeful this won't be a problem with my fifth wheel as I have made all the adjustments I can to the pin box and hitch. I can't adjust the fifth wheel axle height as we have a torsion suspension system. It will be a while before I can hook up and see where it sits but I'm thinking there may be more deflection in the rear with the weight of the pin than there was on the dual.

 

Not sure if it helps, but remember the 2 1/2" of tire difference will only raise the truck 1.25".

 

Got it. I hadn't thought about that. Maybe worrying about nothing.

 

you can also get lowering shackles for the rear end and get it down to level, add air bags so you can inflate them loaded so the truck is level loaded.

 

The over diameter of the tires doesn't usually change with a different rim size. 17" rims have a taller side wall tire and 20" rims have shorter side wall tire.