Upgrade F350 Spare to 20"

[cyellowfin]

My Ford 2020 F350 pickup truck comes with a standard 18 inch spare tire. In most cases this is not an issue on flats with a short distance drive to a service station. However, if I am towing a heavy trailer and have a flat off the beaten path, I do not believe it will be good for my differential if the flat is on the rear tires. I was told if I move a front tire to the back I will be good. This is not a realistic solution when you are stuck on the side of a road. I plan on upgrading my spare to 20". Will it fit in the spare storage bin? What are your thoughts?

 

[Calbar]

I don't think this should be an issue. If you look up the diameter and circumference of both the 20" and 18" tire you will find that they are both identical. They were on my 2019 Ram 3500 so I can't see Ford doing anything different. I would be surprised if that would be an issue.

Rob

 

[Scott'n'Wendy]

What Rob said. The outer diameter is the same so your differential sees no difference. Yes, a 20 will fit where the 18 is now. They are the same size.
If you are going to upgrade, replace the 20's with 18's. Imo, a better truck tire. In particular if you like to go off the beaten path.

 

[marinerjoe]

So riddle me this. If the diameter of the 18” is same as the 20” as both previous comments state, why change? The differential will be seeing the same circumference on both sides so there shouldn’t be any issue. Only replace the spare if the tire age is a concern.

If I’m wrong, please explain.

 

[Scott'n'Wendy]

So riddle me this. If the diameter of the 18” is same as the 20” as both previous comments state, why change? The differential will be seeing the same circumference on both sides so there shouldn’t be any issue. Only replace the spare if the tire age is a concern.

If I’m wrong, please explain.

You are not wrong. But often people think because the wheel rim is a smaller diameter, the tire itself is a smaller diameter. Ford, Dodge, Chevy all offer different size wheel (rim) pkgs but the outer diameter will be the same. It's just a taller tire sidewall in the smaller rim pkg.

 

[cyellowfin]

You are not wrong. But often people think because the wheel rim is a smaller diameter, the tire itself is a smaller diameter. Ford, Dodge, Chevy all offer different size wheel (rim) pkgs but the outer diameter will be the same. It's just a taller tire sidewall in the smaller rim pkg.

That all makes sense. Thank you for your response.

 

[Grandesigner]

Outer diameter must be equal to, and the load rating of the spare must match or exceed the 4 OEM tires that came with the truck. Pretty sure Ford does this for trucks.
My stang spare was too small though and I replaced it with an OEM rim and tire.

 

[Riverbug]

Others have already answered your question but thought I'd add something...I wanted my spare to match the others for a couple reasons. a) I rotate my spare with the others. I like to. It also allows me to remove one tire at a time to rotate. b) If I do need the spare due to blowout (which I assumed might happen in Alaska), I could switch the spare and drive however long I want to but still have an OEM rim in the bad tire's place. Just a preference. So yes, an OEM 20" rim and tire will fit just fine in place of the 18" spare.

 

[440scout]

You are not wrong. But often people think because the wheel rim is a smaller diameter, the tire itself is a smaller diameter. Ford, Dodge, Chevy all offer different size wheel (rim) pkgs but the outer diameter will be the same. It's just a taller tire sidewall in the smaller rim pkg.

Well said! I suppose that a taller sidewall could give a smoother ride because there's more sidewall to flex on harsh bumps.