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Tire sizing
From Wikipedia, the free encyclopedia
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Tire Sizing is also known as "Plus Sizing" on a tire. Most dealers often give the option of plus sizing their set of tires (increasing the overall diameter) at time of purchase, most notably the Toyota Scion brand. However, many tire dealers will offer plus sizing options on tires. This is denoted by "Plus Zero", "Plus 1", "Plus 2", etc. The number indicates the number of inches that the tire will increase in diameter. So for instance, a car with normally fitted 15" tires can have a plus 1 option to have new 16" tires. Plus sizing will enhance the look of the car as well as the performance.
Most modern cars will give owners the option of plus sizing their tires, and some (if not most) owners can have the luxury of a plus zero option without any or significant changes to their wheels.
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The plus zero option does not change the diameter of the tires, but this does not simply this means the new set of tires will be the same as the factory recommendation. A Plus Zero option is almost always the cheapest option available and may enhance the width of the wheel while decreasing the side wall of the tire. So for instance, suppose a car manufacturer's tire recommendation is P195/70R14. A general plus zero option would be P205/60R14, while the side wall of the tire is decreased the width of the overall tire may be increased, giving the driver more "feel" of the road.
The Plus 1, Plus 2, etc. sizing options are usually more expensive. This not only appliest to the tires themselves (as larger tires of the same brand and make are usually more expensive), but wheels must also be customized to fit these new tires. The resulting cost can vary from just a few hundred to a few thousand dollars depending on the enhancements done.
For instance, a Plus 2 option for a car whose factory tires are P185/75R14 may result in P225/60R16 tires. The increase is 2" in rim size but theoreically the overall tread diameter should stay the same. Most tire dealers will also have tires that increase width.
Generally, it is very rare for cars to undergo more than a Plus 3 option.
Advantages may include greater handling and cornering abilities of the car, but this is more a result of the wider tread face and stiffer sidewall of the plus size tires, and can be achieved with tires that are simply stiffer and wider instead of plus sized. Wider tires may decrease braking distances on dry pavement, but see the section on the disadvantages of plus sizing to learn about the physics of plus sizing and the factors that may realistically cancel the benefits of wider tires out.
There is a subjective "appeal" of larger wheels, as in the eyes of some individuals larger wheels are more appealing.
Besides from the obvious cost difference, plus sizing past Plus 1 will seldom give you much added performance. Additionally, the tread life of the tire is much more likely to wear out quicker and many vehicles will need a new set of wheels to match the new set of tires. Larger tires are also much easier to damage, more susceptible to hydroplaning (riding the surface of the water), and less effective in wet weather.
Plus sizing also does not enhance the value of the vehicle (and in some cases diminishes it, since a new set of wheels means the vehicle is not on par with original factory recommended specifications along with not having original factory parts) and SUV/Truck owners will be more vulnerable to rollovers. Ride comfort will also have to be sacrificed in order to deal with performance enhancement.
Furthermore, despite what has been said in other portions of this entry, plus sizing may significantly decrease the acceleration, braking, and fuel economy of a vehicle. Even though the overall wheel diameter measured at the tread may stay the same, the combination of a moving the heavy rim component of a wheel outwards from the center of rotation of the wheel results in a significant increase in rotational mass for each wheel. This increase can result in a measurable increase in the amount of energy needed to accelerate or decelerate each wheel. The corresponding result is an increase in acceleration times and stopping distances. In other words the car gains and loses speed slower. Like all components in any machine, moving weight from one location of a part to another location of a part where that weight has to be moved through a larger distance will result in reduced response times in regards to altering its rate which is otherwise knows as it’s speed. Any change of this manner will have a detrimental overall effect on a vehicles performance.