I just recently discovered that the spare tire on my 2018 F-150 Platinum is a 17". The other 4 are 20". WTF? A truck as expensive as this one was should have the same size spare. That thing will wreck a differential.

 

The rim size should not matter, it is the tire size that matters. As long as the outer diameter is the same. The spare is there to get you to a tire repair shop

 

This. My truck came with 20's and the spare is a 17. But the diameter of the tire is the same as my stock tires. It is also slightly narrower. But they doesn't really matter.

 

You're right if the diameter is the same but unfortunately it isn't. There is over 1" difference. Yes it will get you to a tire shop but if you live in a rural area or go flat on before a long weekend, You may have to drive a long ways before getting the correct tire on the ground again and this is rough as hell on a differential. I repeat, as expensive as these trucks are, the spare should be the same size as the other 4.

 

i Just moved up from an 18" rim to 20", so I will have to get my 17" spare tire replaced with something bigger. I am just going to find the cheapest or used tire that matches the diameter to replace the tire on my spare rim.

 

as long as you aren't in 4wd and you don't have the diff locked you will just fine

 

I'm glad for all of you that are satisfied.

 

Ideally, one would learn this within days of buying the truck, in the process of a) verifying the spare was there, b) learning how to raise and lower it, and c) verifying the pressure in it. Nothing new, been this way for years and years.

 

just enjoy your truck

 

What size tire did you move up to? Moving from a 18 inch wheel to 20 inch doesn't mean a thing as long as the tires are the same circumference. The factory 18inch tire is a 275/65/18 while the factory 20 is 275/55/20. Tires are the same circumference. Now if you moved to a taller tire then the factory then you may need a new spare.