Hi folks......just picked up an '08 F150 King Ranch yesterday and absolutely love it! Look forward to meeting others that get into their trucks as much as I do.

Quick question. I got the 20" Pirelli's (275/55s) as a factory option and just noticed that the 'full size spare' is an LT275/65 R18? If I had a flat with a fully loaded truck, won't the different tire size cause a problem?

 

no because the 275/55r20 is a 31.9x10.8 while the 275/65r18 is a 32.1x10.8 virtually the same size

 

No issues they are pretty much the same size.

 

Thanks for the help guys.

 

As stated above, it is the outside diameter of the tire, not the size of the wheel that matters.

So (assuming that it would clear your brake calipers, etc... which this example would not) you could have a stock 20" wheel with a 275/55/20 tire and a spare that is a 15" wheel with a 265/80/15 tire and they would be almost idenitcal in outside diameter, therefore, a full-size spare. There is just more tire with less wheel on the spare.