How Common is a 4WD Class C?

garyhaupt wrote:
Tires...now there's a topic. No tire shop here will change my tires to larger ones. The ones I have are the ones designed for an E350. They look small when seen from the side..but that is what is supposed to be on. I 'could' buy and install myself but doing so throws all the gearing and electronics out.

Gary ... interesting concerns, but maybe not ones to worry about.

Here's a typical tire sourcing website that shows at least the four tire sizes of 215/75R16, 225/75R16, 235/75R16, and 245/75R16 being commonly used on the Ford Econoline-Series vans: https://tiresize.com/tires/Ford/Econoline/

I believe that many - if not all - Ford E-Series based Class C motorhomes come from the builders with 225/75R16 size tires on them. Of course retrofitting with the 235 and 245 sizes would raise the whole motorhome a bit to provide more ground clearance for sand or rough road off-highway use ... but use of these larger diameter tires may increase the chance of sidewall rubbing in the rear duals unless spacers are used in between the dual tire rims. Also, use of these larger diameter tires would probably be best on only the E450 chassis, as it's lower ratio rear differential would help to counter the loss of tire twisting power (torque) from the larger diameter tires.

On my E450, I went a different route to increase tire diameter a bit without having to be concerned with rear dual inter-tire spacing. I used a tire size not shown on the chart - 215/85R16. This tire is taller (larger diameter) than the common 225/75R16 Ford E-Series tire, but just a little bit narrower. Hence, I get a taller tire for more ground clearance without having to use spacers in between the rear dually tire rims. I'm not concerned with the slightly narrower tread as I'm not into soft beach sand driving/camping. BTW, a narrower tire in the front helps provide a more solid track in the steering on paved surfaces, as well as helping to punch through sleet, snow, and mud layers to reach the solid surface below on paved roadways.

My speedometer reads about 1 MPH slower - which is of no concern - while at the same time my gas mileage is improved slightly over a stock E450 because overall drivetrain gearing ratio is moved to a lower ratio via the larger diameter tires off-setting the 4:56 ratio of the E450's differential.

By using Load Range E, Mud & Snow, 215/85R16 size tires on our E450 24 foot Class C I gain only about 0.6 inch of ground clearance everywhere - but every little bit helps and the DW didn't want too much of a climb up into the cab.