Raven2210

Because the 20's are to expensive to use as a spare. They always go with an 18" spare with a tire size almost the same as your 20" tire/wheel package. Unless you special order a 20" spare.

Cisco1911

thanks for your reply.


So how will it affect the driving/suspension, etc if I have to use the 18" spare? Seems to me that the size difference can affect lots of things. I realize you should only use the spare until you can get the offending tire fixed or replaced but just seems odd to me on the size difference.

1994Vmax

It won't. Like previously mentioned the overall tire diameter is the same provided you have stock size tires on the trucks 20s. A 275/65/18's height is negligible over a 275/55/20. Thus rim diameter is irrelevant.

mack3748

In the codes there is an open 3.31 for the f150 as well. Is the one that is labeled for the 250s is a stronger axle? gear the same just built tougher?