This month we are going to take a closer look at the round black things that connect your car to the ground: tires! We tend to only think of tires when the snow flies, but summer is actually when we put the most miles on our cars and having good tires is important.
Tires these days have many roles to play. The one we think of most of course is longevity, but there are other factors to consider when purchasing tires. Living in Michigan, we need tires that can handle rain, snow and ice, while still providing good handling on dry pavement and in the intense heat. That is a tall order for any tire, which is why two sets of dedicated tires, one for summer and one for winter, is ideal. But this presents cost and logistics problems and isn’t for everyone, so the next best thing is a good set of all season tires.
Tread compound and tread design are the two components that are responsible for creating this happy medium. The compound must be hard enough to give a long life but soft enough to hold the road and give good traction when temperatures drop. The tread pattern determines how well the tire will expel water, slush and snow, as well as how the tire handles cornering and highway ruts. Tire manufacturers are always innovating and improving their designs, but will often continue to manufacture their older designs under private label brands. For example, Cooper makes Mastercraft tires, Firestone makes Fuzion, Goodyear makes Kelly and so on.
In addition to the US and European brands that we are all used to, many of the larger Asian brands have come into the market over the past 10-20 years. Yokohama, Toyo and Sumitomo are long-standing Japanese brands, while Hankook and Kumho are long-standing Korean brands. All of these brands are used by domestic and import car manufacturers as original equipment on their new cars. The Finnish brand Nokian has had a small presence in the US market with their snow tires (after all, who knows winter driving better than the Finns?) but they are now trying to break in with their all-season and performance tires and there are some great deals to be had. Here at Kirk’s we are constantly evaluating new tires as they come on the market in an effort to determine which will be the best values for our customers.
Even the best tires will wear out eventually, and it is important to know when that has happened or is imminent. The first thing to look at is tread depth. New tires come with somewhere between 10/32” and 14/32” of tread depth, depending on the type of tire. As the tread wears, the channels are able to dissipate less water, ice and snow, and by 4/32” their ability to work is greatly reduced. The wear bars on a tire are at 2/32” and are at this point considered “bald.” Sometimes a tire will wear evenly across its tread, and other times the outside edges or center tread will wear first. Outside edge wear, especially on one side only, is often indicative or an alignment or suspension issue. These issues can also cause feathering and cupping, both of which can lead to noise and vibration. Inside wear is often indicative of under-inflation. Did you know that tires tend to lose around 1 psi of pressure each month? They also gain or lose 1 psi for every 10-degree change in temperature, so it is important to check them whenever there are large swings.
Miles are not the only thing that takes a toll on the life of a tire, they also wear out due to age. High heat, sub-zero temperatures, UV light and other environmental conditions will cause the rubber in your tires to break down. This wear usually presents itself in the form of dry-rotting and cracks in the sidewall or tread of the tire. Dry-rotted tires are at a greater risk of blowing out, so it is important to replace them. Tread compounds can also harden, causing reduced traction in poor weather.
Finally, our wonderful Michigan roads can wreak havoc on the lifespan of our tires. Potholes can cause sidewalls to bubble or steel belts to shift, while nails, screws and other road debris can become imbedded in the tires. Impact damage is not repairable, but punctures can be, as the long as the damage is not to the sidewall of the tire. If a puncture is not too close to the side of the tire and is small enough, we can usually patch it from the inside. This is a permanent repair and is much preferable to a plug that goes in from the outside. If your tire ever becomes very low or even flat, do not drive on it! This can damage the tire further and may result in a repairable tire having to be replaced completely. We are working on a road-hazard warranty program that we will be offering soon through Kirk’s, so stay tuned!