Spare tire size

[Darksteel165]

My truck came 285/45 R22s
My spare doesn't say what it is, but there is no tread on it.
I have an older half tread or so 265/65 R18, could I throw that on the 18 inch spare rim?

I used a tire calc and i'm looking at this as the difference

Is that close enough to use? As an actual spare to be driven at regular speeds and have some kind of traction.

 

[Shots]

I'd say you're probably good. My OEM tires were 275/55/20 (31.9") The spare tire was 245/70/18 (31.5").
That a 0.4" difference which is nearly the same as you show there.

 

[Darksteel165]

I'd say you're probably good. My OEM tires were 275/55/20 (31.9") The spare tire was 245/70/18 (31.5").
That a 0.4" difference which is nearly the same as you show there.

Awesome thanks.