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Wheels and Tires:
Manipulating the system
Of course, there is some leeway in what size you choose. Many car owners are installing larger, more attractive rims. This is called plus sizing. A larger rim diameter and smaller profile tire will produce a larger contact patch, increasing handling, cornering and traction.
 If you want to increase your rim size, the general rule is for every inch you increase the wheel diameter, increase the tire width by 10 and decrease the tire ratio by 10.
There is also some leeway for those who want a beefier-looking tire but want to keep their original rim size. Of course, the amount of leeway depends with each tire. Your tire shop should have a manufacturer's size book to guide you, but keep in mind that it's usually better to go up in size, not down. A little extra rubber will form a seal on the bead seat, but too little could spell disaster.
Tire ratings & the need for speed
With the push for higher performance tires, manufacturers adopted a uniform speed rating for their tires. The speed rating is the maximum speed that a tire can carry a vehicle's load. It's important to understand speed rating, even if you don't plan on racing, because it is also a good indication of how your tires will stand up to high temperatures and high amounts of friction that can occur during emergency stops. Most tires use a speed rating of 'S' or above.
The most common speed ratings:
S: for cars speed rated up to 112 mph
T: for car speed rated up to 118 mph
U: for cars speed rated up to 124 mph
H: for cars speed rated up to 130 mph
Z: for car speed rated 149 mph and over:
For example, a tire speed rated at 149 mph and over would carry a 'ZR' in the size designation (275/50 ZR17).
Understanding the speed rating will also help you make decisions about what type of tire best matches your driving habits.
High Performance Tires: These lightweight tires are usually H or Z rated and designed for superior handling and cornering. These tires wear quickly and are typically used on sports cars.
All-season tires have a modified tread pattern for traction in light snow.
Touring tires are usually S, T or H rated. They combine some handling characteristics of a high performance tire with a smoother, quieter ride. Touring tires wear longer than high performance tires.
All-seasons tires manufacturers also refer to these S and T-rated tires as 'mud + snow' tires. The tread is designed for long wear, comfortable ride and predictable handling and are most commonly used on sedans.
Snow tires are low speed-rated tires formulated to stay pliable in cold temperatures and grip snowy surfaces. Snow tires have excellent traction but have trouble cornering and stopping quickly. |
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Article Pages
1. An Introduction to Wheels and Tires
2. Tires
3. Learning To Read Your Tires
5. Valves
6. Tire Pressure Monitoring Systems (TPMS)
7. Tire Inspection
8. Tire Wear Guide
9. Tire Rotation
10. Wheel Assembly
11. Wheel And Rim Construction
Hot Topics
-> 4 Things You Can Start Doing Today To Extend The Life Of Your Tires
-> New Tires Guide
-> Tire Safety Tips
-> What Does It Mean When My Wheels Are Imbalanced?
-> Wheel Balancing
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