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This FAQ: Courtesy of Vulcan Tire Sales

Speed Ratings
Speed ratings signify the safe top speed of a tire under perfect conditions.

1.) Listed inside the size of the tire before the "R" Example: 195/65HR15, the preceding size is an "H" speed rated tire.

2.) Listed in the comparison header at the top of a description page of a tire. (To the right of the picture of the tire.)

NOTE: The speed rating of a tire has nothing to do with the actual size of the tire. So a 195/65HR15 tire can be substituted for a 195/65SR15 tire. However, to maintain the performance characteristics of the vehicle it is recommended that a higher speed rating be substituted.

Common speed ratings are:

Q=99 MPH, 160km/h
S=112 MPH, 180km/h
T=118 MPH, 190km/h
U=124 MPH, 200km/h
H=130 MPH, 210km/h
V=149 MPH, 240km/h
W=168 MPH, 270km/h
Y=186 MPH, 300km/h
Z=149 MPH, 240km/h and over

Tire Rotation
Tire rotation is an important part of vehicle maintenance. Rotating your high performance tires every 3,000 to 5,000 miles as recommended can provide performance advantages, even out tire wear and preserve balanced handling and traction of the tires.

Wear on the tires of performance vehicles is usually greater than on touring or luxury vehicles. Individual wheel positions can have different wear rates and may cause different types of wear on each tire. This is why rotating your tires at the recommended times, even if they don't show signs of wear, is necessary.

Tire wear reduces the tread depth of a tire. When all four tires wear evenly, the wear helps maintain handling, increasing the cornering traction and allows the tires to quickly respond to the driver.

Following the tire rotation advice we've given you will be helpful not only to you now, but also when the tire comes to purchase new tires. When you replace tires in complete sets, you can maintain the original handling balance. If you replace only some of the tires, the tread depth will vary and handling may not be optimum. In addition, when you replace tires in sets you have the option of improving your tires. Tire manufacturers are constantly adding new features and introducing new tires to the market. You can take advantage of the new products when you replace all four tires at a time, rather than trying to find a match for the tires you already have on your vehicle.

While beneficial in many ways, tire rotation cannot correct mechanical problems or problems caused by incorrect tire inflation.
* On front wheel drive cars, rotate the tires in a forward cross pattern (fig. A) or the alternative X pattern (fig. B)

* On rear wheel or four wheel drive vehicles, rotate the tires in a rearward cross pattern (fig. C) or the alternative X pattern (fig. B)

* If your car has directional wheels or tires, rotate them as shown in fig D.

* If your car has non-directional tires that are a different size from front to rear, rotate them as shown in fig. E.



Tire Pressure
Proper air pressure makes tires wear evenly, prevents tire failure and increases handling and traction. While air pressure is responsible for the great task of supporting the weight of your vehicle, it is an easy aspect of your vehicle to maintain.

Inflation pressure is affected by changes in temperature. Because of this, the most critical times to check your pressure are in the fall and early winter months. For every ten degree Fahrenheit decrease in temperature, your tire's inflation pressure will decrease by approximately one psi (pound per square inch). Similarly, a ten degree increase will cause a pressure increase of one psi.

Since tires generally lose about one psi per month, it is important to check them regularly and often. You should be able to find the recommended tire pressure for your vehicle in the owner's manual or on your tire information sticker. Keep in mind that the tire pressure listed is a "cold" pressure. This means it should be checked in the morning before the car has been driven. Also, remember if you check your pressure inside an attached or heated garage, you will lose pressure when you enter the colder air outside the garage. Add 1 psi for every ten degree difference in advance to account for the temperature change.

Alignment
Preventive maintenance is the key when considering wheel alignments. Keeping your wheels aligned will save you tread ware, which saves you money. You will get the best performance and wear from your tires when you routinely align your wheels. Poor alignment is a result of the suspension and steering systems being out of adjustment. This usually results in abnormal treadware. If you notice unusual wear on your tires, check the inflation pressure of your tires, and have your alignment checked.

There are three types of wheel alignments: front-end, thrust angle and four-wheel alignment. The most complete method of alignment is four-wheel alignment. Four-wheel alignment combines front-end with thrust angle and includes a check on the rear wheels as well. Front-end alignments check only the front tires. Thrust angle checks that the wheels are "squared" to each other, preventing your car from going sideways on the road.

Caster, camber and toe are the measurements that must be checked during an alignment. High-speed stability and low speed steering efforts are balanced by caster settings. If you increase your positive caster, you will increase low speed steering efforts and improve high-speed stability.

The amount the tire is tilted away from the vertical is camber. When set properly, camber will allow the tire to function optimally without putting too much of its force on the inner edge while moving in a straight line. Tire wear and handling are affected by camber. Negative camber is when the top of the tire leans toward the center of the vehicle. Decreasing negative camber gives very even wear, but will normally reduce cornering abilities. A tire has positive camber when the top of the tire is leaned outward from the center of the vehicle. The camber angle should be adjusted so that the tire is vertical under cornering load.

Toe is the difference in distance between the front and the rear of the tires. Toe-out is the term used to describe the event that the distance is greater between the front than in the rear. Toe-in, or pigeon-toed, describes the distance between the tires is less in the front.

Mounting & Balancing
tire is balanced when the mass of the mounted tire is evenly distributed around the car's axle. Out of balance tires can have negative effects on both you and your car. While you simply don't enjoy the vibration you hear and/or feel, the life of your tires can be decreased, as well as the life of the bearings, shocks and other suspension components when subjected to prolonged vibration.

There are two main causes of vibration in your vehicle. If it is speed dependent, increasing as your speed increases, and becoming especially noticeable around 40-45 mph, it is most likely a balance-related vibration. The second possible cause of vibration is that the tire and the wheel assemble isn't exactly round. When the high spots on the tire and the wheel match to each other, it doubles the amount of runout , or "hop." If there is a hop the vibration will not end when you rebalance your tires. A hop can often be fixed by simply loosening the tire on the wheel and turning it 180 degrees, reinflating the tire after relubricating the bead. If the problem persists, rotate the tire another 90 degrees, and again 180 degrees if there is still vibration. Doing this allows for the high spot to be tried at each quarter of the wheel, and at one of the points, the tire should be round. From here, rebalance the tire and test drive to check for remaining vibration. If you still feel it, the problem is either in the tire itself of elsewhere in the vehicle.

Uniform Tire Quality Grading - UTQG Ratings
The Department of Transportation requires each manufacturer to grade its tires under the Uniform Tire Quality Grade (UTQG) labeling system and establish ratings for treadwear, traction, and temerature resistance. These tests are conducted independently by each manufacturer following goverment guidelines to assign values that represent a comparison between the tested tire and a control tire. While traction and temperature resistance ratings are specific performace levels, the treadwear ratings are assigned by the manufacturers following field testing and are most accurate when comparing tires of the same brand.

Treadwear:
Treadwear receives a comparative rating based on wear rate of the the tire in field testing following a goverment specified course. For example, a tire grade of 150 wears 1.5 times longer than a tire graded 100. Actual performance of the tire can vary significantly depending on conditions, driving habits, care, road characteristics, and climate.

Traction:
Straight-a-head wet braking traction has been represented by a grade of A, B, or C with A being the highest. In 1997 a new top rating of "AA" has been introduced to indicate even greater wet braking traction. However, due to its newness, this grade will probably be applied initially to new tire lines as they are introduced and later to existing lines which excel in wet braking, but had been limited to the previous top grade of "A". Traction grades do not indicate wet cornering ability.

Temperature:
Temperature resistance is graded A, B or C. It represents the tire's resistance to the heat generated by running at high speed. Grade C is the minimum level of performance for all passenger car tires as set under Federal Motor Vehicle Safety Standards. This grade is established for a tire that is properly inflated and not overloaded.

Note:UTQG ratings are not required on winter and light truck sized tires.


This FAQ: Courtesy of Vulcan Tire Sales