hy..i wonder if u can help my..i have a 99 expedition whit 17 inch rims..now i get 20 inch rims and i get 275-45-20 tires,but theyr too small for this truck..which tire size u think fits better to mi truck in 20s rims..??
thanks for ur help..!!!!!

 

From an engineering perspective, you want to stay as close to the original tire height as possible. Vehicles are designed with tire size as a major factor regarding handling. A little wider is okay, but height is morey important. Just measure your old tire & rim and get tires for the 20" rims that match the original tire height (or as close as possible).

I have slightly smaller Michelins on my 98 Nav and the ride changed for the worse. When they wear out I am going to go back to factory size tires.

 

what is the tire size on the 17" rims you took off? I'm wanting to say they were 31" overall...but I haven't messed with that Generation Ford in a while now
my 08 has 275/55/20 (32") on it. They fit just about perfectly in the wheelwell

 

My nav is a 4x4 with 4 wheel air ride, I run 305/50-20's and the improvement in handling was amazing over the stock crappy conti's.