| All about new cars |
 |
| Looking for a used car ? |
|
| Want to sell your car ? |
|
| Car Pooling |
|
| |
|
Enlist for carpooling in
|
|
|
| |
|
Search for carpools in
|
|
|
| Car Rentals |
|
| Refer Site To A Friend |
|
|
|
Each section of small print on a tire's sidewall means something. For instance, at typical tire descriptor would be "P 235 / 75 R15". Lets understand what each of these means :
Tire Type
The P designates that the tire is a passenger vehicle tire. Some other designations are LT for light truck, and T for temporary, or spare tires.
Tire Width
The 235 is the width of the tire in millimeters (mm), measured from sidewall to sidewall. Since this measure is affected by the width of the rim, the measurement is for the tire when it is on its intended rim size.
Aspect Ratio
The 75 is the aspect ratio. This number tells you the height of the tire, from the bead to the top of the tread. This is described as a percentage of the tire width. Here, the aspect ratio is mentioned as 75(%), and we know the width is 235 mm, so we can infer that the tire's height is 176.25 mm (75% of 235). Obviously, the smaller the aspect ratio, the wider the tire in relation to its height.
High performance tires usually have a lower aspect ratio than other tires. This is because tires with a lower aspect ratio provide better lateral stability. When a car goes around a turn lateral forces are generated and the tire must resist these forces. Tires with a lower profile have shorter, stiffer sidewalls so they resist cornering forces better (see picture below).
Tire Construction
The R designates that the tire was made using radial construction. This is the most common type of tire construction. Older tires were made using diagonal bias (D) or bias belted (B) construction. A separate note indicates how many plies make up the sidewall of the tire and the tread.
Rim Diameter
The 15 following the R is the rim diameter. This number specifies, in inches, the wheel rim diameter the tire is designed for.
Calculating the Tire Diameter
Now that we know what these numbers mean, we can calculate the overall diameter of a tire. We multiply the tire width by the aspect ratio to get the height of the tire.
Then we add twice the tire height to the rim diameter. This figure we will arrive at is the unloaded diameter; as soon as any weight is put on the tire, the diameter will decrease.
Uniform Tire Quality Grading
In the US, passenger car tires also have a grade on them as part of the uniform tire quality grading (UTQG) system. Your tire's UTQG rating tells you three things :
- Tread Wear : This number comes from testing the tire in controlled conditions on a government test track. The higher the number, the longer you can expect the tread to last. Since no one will drive his or her car on exactly the same surfaces and at the same speeds as the government test track, the number is not an accurate indicator of how long your tread will actually last. It's a good relative measure, however, in the sense that you can expect a tire with a larger number to last longer than one with a smaller number.
- Traction : Tire traction is rated AA, A, B or C, with AA at the top of the scale. This rating is based on the tire's ability to stop a car on wet concrete and asphalt. It does not indicate the tire's cornering ability.
- Temperature : The tire temperature ratings are A, B or C. The rating is a measure of how well the tire dissipates heat and how well it handles the buildup of heat. The temperature grade applies to a properly inflated tire that is not overloaded. Underinflation, overloading or excessive speed can lead to more heat buildup. Excessive heat buildup can cause tires to wear out faster, or could even lead to tire failure.
Service Description
The service description consists of two things :
- Load Ratings : The load rating is a number that correlates to the maximum rated load for that tire. A higher number indicates that the tire has a higher load capacity. The rating "105," for example, corresponds to a load capacity of 924.87 kg. A separate note on the tire indicates the load rating at a given inflation pressure.
- Speed Rating : The letter that follows the load rating indicates the maximum speed allowable for this tire (as long as the weight is at or below the rated load). For instance, S indicates that the tire can handle speeds up to 180.246 kms/hr.
|
| <<< Previous | Next >>> |
|
|
|
 |
All about new bikes |
|
Buy / sell used bikes |
|
Message Boards |
|
Useful Stuff |
|
Know Your Car |
|
Your Opinion |
What is most urgently needed for Mumbai's Central Railway (local) train system ?
|
|
