I was just underneath my new F150 and noticed that the spare isn't the same size as my stock tires and wheels. The truck has 265/60/R18 Hankooks on it, the spare is a 245/70/R17 Michelin? Anyone know what gives?

Tiresize.com's converter says this is the same diameter. I suppose that means it's safe to use on the rear axle, correct?

 

Welcome to the club. Everyone gets an odd size tire for a spare. I don't know if anybody knows the reason Ford does that.

 

The spare tires are often just whatever size and brand is cheapest. 90% of people never look at them anyway

 

You get a steel wheel, usually a smaller diameter, with a cheaper tire that nets out to the same diameter as the 4 tires on the road. Saves Ford a couple bucks and saves you from carrying a couple pounds and beats the heck out of the "donut" spares you get with most cars. There are a lot of vehicles these days that come without a spare and give you a can of goop so you can destroy your tire pressure sensor. (I was looking at the Caddy XT5 SUV and the spare tire is an *option*...yuk)

 

Thanks everyone, I feel like I'm at least in good company. I was worried it was some kind of "field swap" situation.

 

I reckon I will have to go look at mine now. I always assumed it was the same as the other 4.
And, it is a well known fact (alleged) that when we rotate the tires we are supposed to include the spare in the rotation.
And, it is a well known fact that all 4 of the wheels on the ground should be of the same size and even same brand. Especially in 4 wheel drive..
Oh well, I gave up on rotating tires many years ago anyway. It has NOT improved tire longevity on any of the vehicles I have had over the past 30 years anyway.
Most cars now have a space saver tire, and more and more new cars seem to come with no spare at all. Go figure.

 

Yae, if that's the case I'll bet there is a Mongrel under there we can use all the help we can get, Good heads up

 

I have 20s and the spare is an 18. I was trying to find a set of 17 steelies for some more aggressive off road/"snow flake" M & S tires, and go with a better street tire for the 20s. I found bunch of 17s at a good price but they had been on Forest Service or other agency trucks and the silver was coming off, they had rust nicks etc. Oh well. So now I found a set of 18s that look good for a good price. I just need to find out how much room there is between the tire and shock with the 18s. There is only 1 5/8s" between the 20s and shock. Cable chains will fit, but only as long as you don't hit a bump, rut or other hole....

But I digress.....

 

Putting a spare in the tire rotation would give you 20% more life out of a set of tires but I don't know of anyone who does that...unlikely that any manufacturer would give you a nice alloy wheel on a spare, especially if it hangs under the truck. I know Jeep Wranglers give you a full matching wheel/tire that hangs on the tailgate, so that would be a good candidate for a 5-tire rotation.

My '02 E150 had a nice factory-size Michelin LTX M/S spare, but on a steel wheel instead of aluminum, so the tire just aged out. (I will note that my '91 BMW 318is does have a matching alloy wheel on the spare but it is inside a trunk well.) And of course, the same tread pattern and even the same tread depth will give you more even traction which is important if you're doing panic stops in the rain or snow...but at least the same diameter tire will keep the spring loading even and keep your limited slip units and transfer case healthy (and provide enough weight capacity if you are loaded or pulling a trailer).

 

 

Same as mine on my XLT. You have the same outside diameter but a 17 instead of an 18. It bothers me but not enough to source an 18 and new tire.

 

I checked mine. 20s on the ground, but 18 on the spare. Same tire manufacturer but different tread design.
Wheel is non magnetic alloy, but cannot see the "outside" of the wheel to tell what it looks like.
It really isn't a big deal to me, but I think Ford should make it known to buyers. The TPM does NOT include the spare and the valve is a mite difficult to reach both to check and to add air when needed. My car spare is in the trunk and easily accessible AND has a TPM.
Alas, another wonderful facet of owning a truck. I cannot even impress my friends and relatives as to how cool I am to own a truck as they all have one too.

 

 

OK. You've been around a while!
Remember when the gas tank used to be in the cab behind the bench seat?

 

Oh heck, you youngsters, remember when the spark control was on the column? Anyone ever drive with just a tiller instead of a wheel? Wood spoke wheels? Chain drive? Total loss oiling?