The tires of your vehicle are most important in terms of your safety and comfort. You must make a point of choosing tires that fit your vehicle, your budget and the way you use your vehicle.

Tires technology has improved considerably over the years. Refinements in construction, geometry and materials have increased the durability and effectiveness of tires for all types of vehicles. At Autotech Performance, we can help you choose the best tires for your vehicle and make sure that you get your money worth!

What you should know about tires

Tires come in a variety of sizes and features. Tires of different sizes or types should not be mixed on one vehicle since different tires have different handling characteristics.

Besides displaying its model’s and manufacturer’s names, each tire is characterized by a coded sequence molded on its sidewall. For instance, a tire with the designation P215/65R15 89H can be described as follows:

• P means that it is made for a Passenger car
• 215 means that it is 215 mm wide (about 8 1/2 inches)
• 65 means that it has a 65 percent profile - the height of the tire is 65 percent of its width
• R is for Radial tire; B would means Bias Belted tire; D would mean Bias-Ply tire
• 15 means that this tire fits a 15 inches wheel.
• 89 is the index of maximum load of the tire; 89 corresponds to 580.66 kg or 1279 lbs; this number multiplied by four (=2322.64 kg or 5116 lbs) represents the total weight that should never be exceeded by your vehicle and any extra load it may carry.
• H is the speed index that indicates the maximum speed allowed for the tire; for instance, the H code corresponds to 210 km /hr which is standard for most passenger vehicles.

The tread wear index is also inscribed on the tire. It indicates how “well” the tire wears. For instance, a tire graded “420″ should last about 4.2 times longer than a tire rated at “100″. However, driving conditions and driving style affect tread wear differently. This index should not be used to compare tires from different manufacturers.

The traction index qualifies the capacity of the tire to brake on a wet road. This index is measured while braking in a straight line and does not qualify tire traction during turns.

The temperature code indicates the tire resistance to heat: the code “A” indicates the highest resistance while a “C” translates the minimum resistance level currently required for standard vehicles.

The date of manufacturing of the tire is also indicated on the inside edge of the tire near the rim. The last 4 digits of the serial number (called DOT) indicate the week and year of manufacturing: for example, 1107 would mean that the tire was manufactured in the eleventh week of 2007. Notice that the life of a tire is 6 to 7 years. It is good practice to check these numbers on all tires that you buy to make sure that they are not too old. Old tires begin to deteriorate after 6 years even though they were never mounted on a vehicle.

The maximum tire pressure is printed on the sidewall of the tire. It should never be exceeded!

Check your vehicle’s owner manual or look on the driver’s door to find out the recommended tire pressure for your vehicle. You should verify the tire pressure regularly in order to maintain the recommended pressure and to detect possible slow air leaks. Note that a tire can lose up to half its pressure and yet not appear flat.

Maintening an adequate tire pressure is probably the most important factor in ensuring tire longevity. Low tire pressure is indeed the leading cause of tire failure. With properly inflated tires, your vehicle’s suspension does work better and you get both a better handling of your vehicle and a better mileage.

Excessive or insufficient pressure in a tire can be assessed by looking at its wearing pattern:

• If the tread is wearing on the outside and inside, the tire is under inflated.
• If the tread is wearing in the middle only, the tire pressure is too high.

All tires come with wear indicators that tell when the tire should be replaced: if you see a solid bar running across the width of the tire, it is time to replace it!

Nowadays, most vehicles are equipped with a Pressure Monitoring System that indicates any discrepancy between the prescribed tire pressure and the actual one. The system monitors each wheel independently. Only wheels marked with “PAX System” can be monitored by such a system.

Wheel alignment is also an important factor tin minimizing tire wear. Properly aligned wheels considerably extend the life of tires. The wearing pattern of the tires can indicate if the wheels are out of alignment. Notice that alignment should be done on all four wheels at the same time: an alignment done on only the front wheels will cause the rear tires to wear adversely.

Radial tires should be rotated regularly from front to back to even out their wear - they must be kept on the same side.

Most vehicles now come with a “space saver” spare tire. It is much lighter and less durable than a regular tire. The inflation pressure is usually higher than for a standard tire because of its smaller size. Pressure in the spare tire should be checked at least once a year to make sure that the spare tire is functional when needed in an emergency.

How to change a tire in an emergency:

• Park in a safe and level place - keep driving slowly on flat tire until reaching a safe place
• Turn on emergency flashers - set hand brake with car on “Park” or in “1st gear”
• Remove spare tire and jack from storage compartment
• Follow instructions written on jack or in owner’s manual
• Position jack as indicated and start lifting car
• With wrench positioned horizontally on lug, use foot to loosen each lug counter-clockwise
• Raise car until wheel is clear of ground - remove lugs
• Replace defective tire with spare tire and install lugs
• Lower car until tire touches ground
• Tighten all lugs with foot, clockwise
• At earliest convenience, repair or replace defective tire and return fully inflated spare tire to storage compartment for later use.

How are tires made?

Tires are made of fabric, steel and rubber. Attached to the wheels of a vehicle, they provide contact between the vehicle and the surface over which it travels. Each modern automotive tire supports approximately 50 times its own weight. Compressed air within the tire carries 90 percent of the load while the tire’s complex structure - of fabric, steel and rubber – carries the remaining 10 percent.

Wheels are metallic cylinders that link the tires to the suspension system. Even though wheels are often chosen for cosmetic purposes, their function is critical. The wheel is a major component of the suspension: if it is too small, it interferes with braking operations; if it is too big, it interferes with steering operations. Similarly, a wheel that is too wide causes the tire to wear out prematurely and put stress on other suspension parts by moving the center of balance of the suspension further out than it should be. An out of balance suspension then makes the vehicle very unstable in turns. This shows how important it is to select the right size of wheels (and tires) for your vehicle.

The tread is also a critical feature of the tire. It must provide a constant and solid grip on the road in order to ensure control and safety. Each tread pattern is characterized by the geometrical shape of the grooves, lugs and voids. Tread patterns are most important in determining the right tire for any given driving circumstances. For instance, when you are driving on a wet surface, you benefit from a tire with a tread pattern that wipes away water from the small contact patch at the bottom of the tire. Hence, continuous channels that direct water from the center to the outside of the tire provide the best wet weather grip. For dry surfaces, a tire with “no tread at all” would provide the best handling of the vehicle! However, since tires are used on various surfaces and in different weather conditions, you need a tread pattern that provides both durability and adequate handling under normal driving conditions.

On each side of the tire, the sidewall is the part that bridges between the tread and the bead. Tire sidewalls have two purposes: first, they flex up and down, cushioning the vehicle from road irregularities; second, they transfer loads of energy from steering, braking and accelerating to the tire tread. The beads are hoops of steel covered by rubber that reinforce the area where the tire sidewalls and the wheel’s rim meet. The diameter of the beads determines the tire’s size.

Reinforcing cords are arranged beneath the surface of the tire in a crisscross pattern. They give the tire its strength. Classes of tires are established with regard to the direction of the cords:

• A bias tire (or cross ply) has cords positioned in a crisscross pattern between plies - or layers - of the tire;
• A belted bias tire has two or more bias-plies of reinforcing cords to which stabilizer belts are bonded directly beneath the tread;
• A radial tire has cords that are running in a hoop fashion from bead to bead.

The radial tire has reinforcing plies running only on the tread area of the tire. The lack of bias sidewall reinforcement makes the radial tire more flexible which gives it a better grip and a longer life. It also gives the radial tire its under-inflated look.