They’re too noisy, they wear out too fast, they’re expensive, and most people only pay attention to them when they go flat. Yes, I’m talking about your tires.
Typically neglected and ignored, these are some of the most important components of your tow vehicle or RV. If we’re going to talk tires, perhaps I should explain the mysterious code found on the sidewall of tires.
I’ll use a P225/60R16 as an example from one of our police cars.
Here’s what it all means:
– P = Passenger car tire. There are others, such as LT for light truck.
– 225= This is the width of the tread face in millimeters (there are 25.4 millimeters in an inch).
– 60= The height of the sidewall of the tire is 60% of it’s tread-face width – sometimes called the tires “profile”.
– R= Tire is a radial. Radial means the cords that hold the structure of the tire together run at 90º to the direction of travel for the tire (ie: crosswise).
– 16 = Tire is designed for a 16″ wheel.
There are many other numbers and symbols on the sidewall of a tire. I got this from a NHTSA/DOT site:
There are other numbers that you should be aware of when tires shopping. Load carrying capability is important to those of us that RV. Every tire made has it’s load carrying ability in pounds and Kg stamped in the sidewall of the tire. Also listed is the maximum inflation pressure for that tire.
Passenger car tires will also have a wear and traction rating present on the sidewall. The traction ratings are A, B, and C, with A being the best. The wear number is based on government testing, and is represented by a number in the hundreds. A tire rated for 140 wear would be likely to be found on a sports car, and would wear very quickly. A tire rated at 500 would likely be an all season type, and would have a much longer life. The numbers can be directly compared as well. A tire rated at 250 will last half as long as one rated at 500 if used in the same conditions.
Tire maintenance is important. The single best thing you can do for your tires and your safety is regularly check the inflation pressure. But, what inflation pressure to use – the one provided by the vehicle manufacturer that is listed on the driver’s door post, or the one listed by the tire manufacturer listed on the tire sidewall? For the best ride, use what’s on the vehicle. For the best load carrying capacity, use the maximum listed on the tire sidewall. A good visual inspection every once in a while is a good idea too. You’d be surprised what you see. I casually check my trailer tires when I walk by, but before a long trip, I actually get down on the ground and look at each tire. I found one a while ago that had 90% of the tread left on the outboard side, but only 10% on the inside. The inside of the tire was hard to see during the quick glance, but easy to see when I got down and looked. I got the axles aligned and all was well again.
Most tire failures are caused by under-inflation. Ever try to break a piece of plastic or metal by bending it back and forth repeatedly? What happens to the spot where it’s bending? It gets really hot doesn’t it? When your tires are under-inflated, the sidewall flexes back and forth every time that section of tire is at the bottom, and bears the weight of the vehicle/RV. In effect, the whole sidewall begins to heat up rapidly, and will eventually start to come apart — usually on the inside of the tire first, where you can’t see. If you have tires that have been run under-inflated for any period, get them demounted and examined by a professional. I have seen tires that look fine from the outside be full of shredded rubber on the inside.
The newest idea for tire is filling them with nitrogen. Why nitrogen? Well, among other things, nitrogen molecules are larger than oxygen molecules, and therefore the tire holds pressure longer. The nitrogen cannot escape past the bead seal or make it’s way through the tire wall. Nitrogen also doesn’t react with changes in temperature like normal air does. The pressure stays more consistent in all operating conditions.
Tires even have wear indicators that tell you when they’re due for replacement. Here’s what the look like:
You can see the wear bar in the middle of the yellow section below the level of the tread blocks. When this is even with the rest of the tread, it’s replacement time.
There is a common misconception that worn tires don’t grip as well as new ones. In reality, for dry asphalt, the opposite is true. Less tread on dry roads yields the best handling and grip. The voids in the tread face are there to evacuate water and slush. That’s when worn tires become a huge liability. They can hydroplane on water. Hydroplaning is when the tire no longer makes contact with the surface, but floats over it on the surface of the water. This means your grip with the road is gone, and of course that can have dire consequences.
This tire is almost worn out. The wear bars (pen) are almost even with the tread face.
Buy the right tires for the job. We have a saying here in Canada. All season tires are actually 3 season tires. They’re not good for winter. If you regularly drive in ice and snow, a set of winter tires is a good investment. They have several design features that make them grip better in ice and snow. The have many tiny little cuts, called “sipes” that evacuate water and allow the tire to grip ice better. The tread is made of a different compound that doesn’t become as hard when used in cold weather. Some even have tiny shards of ground up walnut shells as an ingredient in the tread compound to help bite into ice.
Pay attention to your tires, check the pressure monthly, and buy good ones when they need replacement.
See you next week!