I spent late yesterday morning at the one tire shop in the Minneapolis area that could get the tire I needed in stock without having to have it shipped in from out of state. I ended up in a first ring suburb so close that they list their address as Minneapolis, though they are not technically in Minneapolis city proper, but rather, in St. Anthony. At least I didn’t have to drive very far to get my tire. I view of that, I thought a good topic for today would be tires.
Tires are a part of the car that doesn’t get much thought usually until something goes wrong. Then, they become very important to whether or not you can even drive your automobile. To that end, I wandered around the Goodyear shop where I was actually buying a Dunlop tire (they’re owned by Goodyear), and took some photos of the different tires they had on display so we could take a look at them today.
We’ll begin with a quick discussion of tire size. If you’ve ever looked closely at your tires, you’ve probably seen something that looks similar to the close up photo I’ve got posted. “P265/75R16”. What does that mean? Lets break it down.
*The “P” stands for “passenger car”, other designations would include “LT” for light truck, “T” for “Temporary” -you’ll see this on your space saver spares, or “ST” for “special trailer”
*The next 3 digits, in this case “265” tell you the width of the tire from side wall to side wall in millimeters. This number is also called the “nominal section width”
*The “/” mark is just to break things up a bit.
*The 2-3 digit number, “75” in this case, indicates the height of the sidewall of the tire as a percentage of the total width of it, also called the “aspect ratio”. If your tire doesn’t have one of these numbers, then you can assume your aspect ratio is the default 82%, and if there’s a number here that’s bigger than 200, then it’s indicating the diameter of the tire instead of the aspect ratio.
*The “R” signifies how the tire is constructed. Tires have cords that run through them within the rubber to give structure and stability, kind of like rebar in concrete. In this case, R means radial, which is what most cars use nowadays and means that the cords run parallel to each other. Radials tend to last longer and stay cooler. Other letters you might see would be “B” for Bias Ply, which means that the cords are at an angle relative to each other as they overlap their piles of reinforced rubber… it’s kind of the same thing as “D” for Diagonal ply.
*The 2 digit number, in this case “16” implies what size rim that tire fits on.
Now that we’ve had a refresher in our tire talk code, let’s look at some tires.
First, we have the snow tire. Goodyear is comparing tires to shoes in their marketing material, and it’s not a bad way to explain stuff when you’re trying to give people an idea of what’s what. Thus the “snow shoe” graphic on the display. The deal with snow tires is that the material they’re made of is formulated differently than summer or all season tires. They’re softer, and don’t stiffen up as much as other tires when the temperature plummets, so they can still provide excellent grip in cold conditions. The sipes -the itty bitty grooves that crisscross the tire- are more plentiful than on other tires, and, along with the design of the tread grooves (bigger grooves than the sipes), are designed to bite and claw through snow and ice. You don’t want to use your snow tires in summer because the rubber is very soft, and you’ll wear them out quickly… though you’ll get some good, sticky grip and traction while doing it.
A summer tire has larger tread blocks (the spaces between the tread grooves) than a winter tire, and is made of a stiffer rubber that isn’t going to be much good to you in snow and ice. The tread grooves are wide and often designed to fling rain water from their paths. These can also be called performance tires in some cases. Here is where you’ll see a lot of directional rotation tires, meaning that they’re designed to only roll one way, which gives you more precise performance, but also means your options are limited when rotating them unless you want to take them all the way off and have them remounted on their rims. Directional rotation tires aren’t limited to summer tires, though generally, they‘ll be some type of performance tire. My snow tires are directional rotation tires, as are my summer tires. The photo I have is a computer generated image that the store uses for promotion, but it’s a good illustration of a directional rotation performance tire.
There is also a more extreme tire called the Racing slick. It has no tread blocks because it has no grooves or sipes. This tire is for racing applications and provides 100% contact between the rubber and the road. You don't want to use these for driving in rainy or icy weather unless you really like hydroplaning.
An All Season tire is expected to do it all, so you can also expect some compromise. The grooves and tread blocks are sized in between summer and winter designs, and their formulation is at a middle ground, too. All season tires don’t really give you the best of both worlds so much as they give you the mediocre of all worlds. Depending on how extreme your driving conditions are, this could be a happy medium or a miserable middle ground. Most cars you’d buy new from a manufacturer will come with all season tires.
When we move into larger vehicle territory, we start to see work truck tires and tires that tout some off road capability. The more aggressive work truck tires would likely be seen mounted on a vehicle that’s hauling stuff around a construction site. Take a look at those chunky, nubby tread blocks and the massive relief between the grooves and the peak of the blocks. They give excellent grip and bite on the dirt and gravel surfaces they are expected to traverse, but the ride quality is miserable.
For SUVs and non heavy duty work type applications, you’d get a tire that imparts a smoother ride quality but can also get some grip if you happen to stray from the beaten path.
Tires can make a huge difference in the ride and handling of a vehicle. Next time you have to buy new tires, take the time to really consider what you’re after. Buying the least expensive ones, or tires with the highest mile warranty on them may seem like a money saving way to go, but it may also compromise your vehicle’s performance, so keep that in mind.
No comments:
Post a Comment