Full-sized spare? Put it in the rotation

This is a moot point for many, because most passenger cars are equipped with either a temporary-use mini spare, or no spare tire at all. But for those SUV and truck owners with a full-sized and matching spare tire, including those tires in the rotation schedule can extend the lifespan of the entire set substantially, and save you money.

But first, let’s back up a bit. Why should you be rotating your tires in the first place? Because every wheel position on any vehicle submits those tires to different levels and types of force. This will cause different wear rates and patterns. Think it doesn’t make a difference? Try skipping one or two rotations on the average front-wheel-drive vehicle, and then let us know if you’re happy with the new noise from those rear tires when they finally get back up to the front.

Most front-drivers — especially minivans — have stiff rear suspensions that seldom get put to work, leaving the tires to take more of a beating than the shocks or springs. This will cause a chopped wear pattern that will make you think you’ve got heavylug off-road tires when you mount them up front. On just about any type of vehicle, avoiding rotations will shorten tire lifespans.

In the early days of radial tires — the early 1970s — some tire manufacturers had problems with belt separation when the tire’s rotation direction was reversed. Those problems were cured with new bonding processes by the late ’70s.

Before asking your shop to include your spare tire in a rotation, check the side walls. Tires can’t be unidirectional, meaning they’re designed to rotate in one direction only. These tires will have a directional arrow embossed in the side wall and sometimes the word “unidirectional.”

As well, the spare tire must be of the same design and wear rating as the rest of the rubbers. Vehicles built with staggered setups (differentsized tires on the front versus the back) can’t have any rotations, either.

You’ll notice a change in noise when changing a tire’s rotation direction, but if you stick to your recommended schedule (usually every 10,000 to 12,000 kilometres) it shouldn’t be too objectionable and will quickly lessen with distance travelled. If you do your own rotations and may have forgotten which way a particular tire rotated, simply take the flat part of your palm and run it in both directions on the tire’s tread face; one direction will feel decidedly smoother than the other. With the tire’s outer side-wall facing you, the path your hand takes on the smoother sweep is the opposite direction than the tire was rotating.