# Tire Basics for Dummies



## CARiD (Jul 15, 2009)

Finding the right tire to fit on a vehicle is not easy. If you want proof of the difficulty, just look at the caravan of tire trucks that follow rally teams around the world. There are different profile tires, there are different rubber compounds and there are tire tread patterns for all kinds of weather conditions. Unfortunately, you cannot change your tires according to the road and weather conditions of the next 15 miles of road in front of you, as the rally teams do (and even they don't always get it right). You will have to choose tires that perform well most of the time and adequately when the conditions are less than ideal. The tires you buy must have a load rating and a speed classification that fit your vehicle. The load rating is particularly important to note when you buy tires for big SUVs and trucks, as the same size tires and wheels might come in different load ratings, one for passenger cars and one for SUVs and trucks.

*Racing tires show the basics of tire choices*

Let's talk about performance car tires first. The extremes of racing make it clear which factors you have to take into account when you decide which tires to buy. For racing there are two basic types of tires: Slicks for dry and smooth asphalt and Rain Tires for wet conditions. The slicks have no pattern at all and are made in a sticky rubber compound. This is to maximize traction, and it works well as long as the surface is absolutely dry. Add a little water and the game changes completely. The wide and smooth slicks surf like surfboards on top of even slight moisture. The water acts as a lubricant between the road and the tire surface, and the driver must slow down enough to make the tires sink down through the water, or the car will spin out of control. This is applicable to your everyday road tires too. Wide tires, with little or no pattern that can drain water away, are very prone to aquaplaning. This is why there are laws on tire tread depths for road tires. Driving with tires that cannot drain water away is extremely dangerous as soon as there is water or moisture on the road.

*Different tires for different climates*

Even slicks come in a number of variations, with rubber compounds for different temperatures and pavement surfaces. One important aspect is how fast the tires wear. Soft tires (like Pirelli tires) provide better grip than tires made in harder compounds, but wear more quickly. If the soft tires wear too quickly, the extra pitstop to change tires can mean that the race is lost. If a team chooses tires that are too hard they might lose the race by being a fraction of a second slower on each bend. Choice of tire compound is important for road wheels too. You probably want to get as many miles as possible out of your tires, but you also want tires that provide a good grip on the road for safe braking and cornering. If you live in a hot climate, you will probably want a little harder rubber compound than people living in the cold of the north, to get comparable grip and wear.

*Don't kill your wheels on potholes*

If you live in a part of the country where rains are rare and the road surfaces smooth, you will have little problems with wide, low profile tires that come close to being slicks. (For road use you will still want some tread pattern.) If you live in a state where the frost breaks up potholes in the road surfaces and the road maintenance budget is insufficient, you will probably want a higher profile tire to have a bigger air cushion between your expensive custom rims and the edges of the potholes, and to avoid that every road trip becomes a shaking experience.

*Severe grooves for severe rains*

The more difficult the weather is, the more ridges, grooves and siping you want in the tire tread. The ridges running along the perimeter of a tire act like very narrow wheels that cut through the water surface, providing direct contact between the tire and the road. The grooves along the ridges drain water out. These longitudinal grooves are also important to the directional stability. Some or all of the ridges are divided into blocks, providing lateral edges that break the water surface and lateral channels that drain the water out of the tire. Many tires also have fine cuts, "siping," in these blocks, creating thousands of edges that cut through the water when the brakes are applied and the rubber between the cuts bend and show off their cut edge.

On the other hand - the more cuts and grooves, the less surface is put on the road in dry conditions. The movements of the rubber blocks in a tire with a heavy pattern can also build up heat and cause excessive tire wear. Lateral grooves can also cause excessive noise in dry weather. Thus, the choice of tire tread should be made with an eye to the local climate conditions. For everyday driving, the natural choice is an all-weather tire from a major tire manufacturer. They come in many variations, each with a slightly different compromise between the factors mentioned above. Choose one that fits your driving style, driving conditions and your comfort demands. If you live in an area with heavy winter climate, we recommend that you also get a separate set of winter wheels with tires specifically designed to perform well on snow and ice.


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