I have a 2006 is250 awd. I upgraded from the 17 inch wheel to 225/40-18. I was told by a mechanic that the spare tire has to be the same circumference as the new tires to prevent damage to the differential/transmission because of the awd. The spare is 125/70-17 and is smaller that the OE rims. Will the original spare work with the new tires

 

In a word - YES! But, since it is a donut spare, it is not meant to be driven above speeds of 50MPH or for long distances.

Lou