Most of us buy tires only as a replacement to what we are already using. When we bring the car in for oil change, usually that's when most of us get the bad news that our tires need replacement. So the next step is to either buy their tires or drive over to a big chain store and buy whatever tire is the tire guy tells us that is on sale and also they recommend all sorts of "safety" procedures which also comes with a price. So how exactly do you protect yourself and understand what is what? This guide is designed to help you understand and avoid misinformation.

How To Check Existing Tires

First let's decide if the tire is even bald enough to need replacement. What is a bald tire anyways? Well if you think of the tread on the tire as hair, just how thick is the hair? When the tire is bald, it basically has no tread left and looks like a bald head. On dry race roads, you want the tire to be bald to get maximum rubber to the road for best traction. But guess what? It can't handle rain nor dirt on the road. Even if you can't see it, there are little pebbles and sand all over the road which will make your car slide if your tires are bald.

So let's get back to checking the tire. First look at the tire overall. There are three places to check where the rubber meets the road. First is the middle of the tire. Then the two outside edges. Assuming your car is properly aligned and the tires are properly inflated, you will not see any difference in tread wear. If you find a difference, we've got a problem. If the center wears faster than either side, that means the tires have been over inflated. If both the outside edges are wearing faster than the middle, that means your tire is under inflated. Then finally if one side of the tire wears out faster than the other, we have a camber issue. That is when top of the tire is either tilting in or out compared to the bottom. All these issues can be fixed and may not require a new tire. It all depends on how much tread is left. The more tread that is left, the higher the chance you don't have to replace it.

So how much tread is enough tread? On new tires it's easier to tell. In the grooves (between the tread) you will see what looks like extra bumps. Those bumps are wear indicator. When the tread wears down to those bumps, it's time to get new tires.

On older tires, it's best to use the nickle trick. Get an older nickle (not any of the new US ones) and then aim the head into the groove. If the tread touches the head, time to start thinking about purchasing new tires.

Tire Measurements

Look on the tire you want to replace. On the side, you will see a couple things:

P195/55R16 80Z    Tread Wear 300 Temperature A

• P = Passenger (you can have LT = Light Truck, etc)
• 195 = Width in millimeters of the tire measure across the thread.
• 55 = Aspect Ratio of the sidewall compared to the width
• R = Radial (nobody uses the old tires anymore)
• 16 = Diameter in inches of the rim
• 80 = Load rating
• Z = Speed rating
• Tread Wear 300 = How long in percentage will the tires last. A good rule of thumb is 100 = 15,000 miles. 300 = 45,000 miles
• Temperature A = How hot can the tire run. Usually goes hand in hand with the speed rating.

Buying Tires

When you buy tires, there are the must have's and the nice to have's. Must have is the correct size. It must fit the rim and be properly proportioned otherwise the speedometer is thrown off. From above, you want to match: P195/55R16. At times you can buy wider tires: 205 instead of 195 but you have have to get a smaller ratio and sometimes the rim won't support a wider tire. Safest bet is to get the same type.

For should have's, you want Z rated tires. These allow the tire to travel over 100mph... along with Temperature rating of A. Where it gets tricky is Tread Wear.

The higher the Tread Wear, the stiffer the tread is. Stiffer tread performs worse because they aren't gripping the road as well. But at the same time, if the tread is too soft, they don't last long. High performance machines like Ferrari has extremely soft tires where you are lucky if they last 15,000 miles. While cars like minivans and economy cars, the tires last over 60,000 miles.

The next thing to consider is tread pattern. Tread pattern for the most part determines if the tire performs better in dry, wet, muddy or snowy conditions. Once again cars like Ferrari will focus their tire to work better in dry while SUV's will concentrate more on mud and snow. Another interesting note is that tire tread also effects gas mileage. The smoother the tread, the more miles you can travel per gallon. That's another reason why SUV's don't get good gas mileage.

Additional Things to Consider

• Tire Rotation - In the old days, you would want to rotate tires in an X pattern. Front left tire to rear right and then front right to rear left. Now adays, tires are becoming more directional again so you can only swap front to back on the same side.
• How many to Buy - Only buy in pairs. Buy the front two or the rear two. Remember not all tires are the same size and of the same quality. Unbalanced tires are very dangerous because it effects the steering of the car.
• Wheel Balance - Wheels should always be balance prior to mounting on the car. This prevents the wheel from hopping along on the road.
• Alignment - This you will need in order to make sure your tires aren't tilted in any funny direction. Not only is it unsafe, it will cause tires to wear prematurely if not properly aligned.

Final Thoughts

For the most part, getting a decent tire isn't rocket science. Stick with well known brands with all season capability and you should be fine. Those wishing performance tires will have to pay a lot more especially if the rim size is increased (which I'll probably write another guide for). Make sure to get an alignment and the wheels are balanced before mounting. Check to see what their warranty is and you should be good to go. Hopefully armed with this type of information would at least make you less prone to get ripped off.