Running a smaller spare with larger tires, and a G80..

[adriver]

I have to add this after taking an aspirin and looking at your math again-i think your off on tire circumference-which is tire diameter 265/65/18 is 31.56 not 99.15 like you said big diff so would be 263 ft per minute before lockup. To use a tire size that comes standard, 265/65/18.. 265/65/18 has a circumference of 99.15" (Start with your tire size and circumference)

On that tire size 99.15" is the circumference.. That's the distance for 1 revolution. I was trying to figure out how much of a difference (in tire size (circumference difference), & speed) it would take before you reached 100rpm difference.

 

[corvette744]

Gotcha so your taking pie 3.14 multiplying by 31.56 to get 99.1 let me go get another aspirin.So just to reinstate your question yes you can use it just hope you dont spin the rear tire the spare is on in anyway faster than the other and your fine.