Can I Use a Non-Matching Size Tire as a Spare

Updated 03/06/2020 | Published 03/05/2020

Question:

Hi can I use a mounted ST 225 75 R15 as a spare for a trailer with 700-15 tires

asked by: Sherry

Helpful Expert Reply:

Unfortunately a 7.00x15 tire is going to be about 1" larger in diameter compared to a ST225/75r15 tire, and you really can't run tires of 2 different sizes without creating issues that will surface with long term use; namely uneven tire wear and the potential for another blowout.

You could potentially get away with this as a spare tire as long as it's only used to get yourself from the point of malfunction to the nearest tire shop but you would want to make sure that the capacity of the spare is higher than the tire it's replacing.

At the end of the day, you might be best suited upgrading all of your tires to a non-metric tire size so that you're able to easily find replacement tires in the future. The Kenda Karrier ST225/75R15 # AM10256 tires you were looking at are a Load Range D tire that would make a great replacement option for all of the tires on your trailer, as well as a spare tire.

expert reply by: Erik B