Ford E450 Tire Size

pnichols wrote:

How much power loss from large diameter tires you experience climbing up grades of course has to do with how much weight you end up with on the E450 chassis after your build.

As you know the E450 has a 4:56 rear differential ratio, which is a pretty good pulling ratio - compare it to the often lesser ratios in everyday heavy duty pickups. Our 24 foot E450 motorhome is only around 11,800 lbs. loaded, and that rear differential ratio is way over-kill on pulling power up grades. It's great for creeping along off-pavement, though, and when going up grades that ratio helps keep any transmission torque conversion slippage at a minimum as well as keep engine and transmission heat low.

By the way, 215/85R16 tires have a larger diameter than 225/75R16 tires and 215/85R's are what I now run on our E450. Also, in Load Range E they are rated for the same loads as 225/75R's. I also like the 215/85R's better because they're slightly narrower so there's better hot weather cooling air flow between them in the rear dual sets.

I haven't had the opportunity to try out the 6.8L on any grades yet. I know on flat land it has plenty of power but fuel mileage was worse than my 2003 Freightliner Columbia "bobtail" which weighed in at 21,500-lbs empty. Bobtail I would consistently get between 9-11mpg (@ 66mph) with the 12.7L Detroit, 13-speed, and 2.93-gears. When I would carry my Jeep on the back it didn't even know it was there. Was hoping to get slightly better MPG's with the E-450 to haul my Jeep.