Zeigler Lincoln Mitsubishi of Kalamazoo

Viscous planing

Viscous planing is caused by a thin film of water, no more than half a millimeter thick, between the tire and the road surface. This thin film of water separates the molecules in the tread compound from those in the road surface and the inter-molecular bonds are broken. The tire loses almost all its grip and slippage is unopposed.

Aquaplaning

With aquaplaning, the tire gradually loses contact with the road surface as a thick layer of water (> 0.5 mm) is forced under the tire by the speed at which the vehicle is moving. As the speed increases, the water cannot get away from the front of the tire fast enough and the pressure begins to mount. The water is gradually forced under the tire until the tire loses all contact with the road.

Aquaplaning progresses through three stages:

• The water pressure rises as the tire speed increases.
• Some of the water is displaced through the tread pattern and around the sides of the tire.
• The tire gradually lifts off the road as the water pressure becomes greater than the contact pressure.

The grip is reduced considerably resulting in:

• Increased braking distance.
• Loss of steering.

Speed

Images of a tire in contact with a film of water and dye at specific speeds:

Tread Pattern

Advanced techniques are used to establish how the tread evacuates water:

Contact area and water displacement rate.

6 Functions Of A Tire

Today, tires and cars have reached such a high degree of development that drivers tend to forget that the tire is the only point of contact a vehicle has with the road: it is the tire which has to bear the load, roll, steer, transmit forces, be long lasting and absorb shocks.

1. The tire steers the vehicle with precision regardless of road and weather conditions. The vehicle's ability to keep a straight path depends on the tire's ability to maintain its course. The tire has to absorb transverse forces without deviating from the vehicle's trajectory. Generally speaking, each vehicle has a particular inflation pressure for the tires of each axle. By respecting the differences in pressure between the front and rear axles, optimum driving precision can be obtained.
2. The tire supports the vehicle when it is stationary, but when it is in motion the tire must resist considerable load shifts during acceleration or braking. A car tire has to carry over 50 times its own weight.
3. The tire "drinks up obstacles" absorbing bumps in the road to make life more comfortable for driver and passengers as well as helping the vehicle itself to last longer.

The main characteristic of the tire is its flexibility, especially in a vertical direction. The great elasticity of the air contained in the tire enables it to withstand successive deformations caused by obstacles and uneven road surfaces. The correct pressure therefore ensures a reasonable degree of comfort while maintaining the correct steering capacity.

4. The tire rolls more evenly, in greater security, with lower rolling resistance, giving greater driving pleasure and controlled fuel consumption.
5. The tire transmits forces: the engine's power output and the braking forces. How well these forces are transmitted depends on the quality of those few square centimeters of tire in contact with the ground.
6. The tire lasts i.e. continues at its best performance levels for millions of revolutions of the wheel. The wear pattern depends on how the tire is used (load, speed, road surface, condition of the vehicle, driving style, etc.), but especially on the quality of that contact with the ground. That is why tire pressure plays such a major role.

It affects:
- the size and shape of the contact area
- the distribution of forces to the different parts of the tire in contact with the ground.

The tire's six functions guarantee security, comfort and economy.

These must be guaranteed for the whole lifetime of the tire, but it is up to the user to take a few elementary precautions.

The tire needs air in order to function correctly and be long lasting.

Its inflation pressure therefore must be checked regularly. This is because the tire's precious air escapes molecule by molecule through the (albeit low) natural porosity of the rubber as well as through accidental causes such as leaks in the valve or at the rim, or slight damage to the tire, etc.

The inflation pressure conditions all the tire's functions: security, economy, and comfort. Furthermore, the wrong pressure adversely affects all its performance areas. Regular quick checks can avoid a lot of problems.

How To Read the Sidewall Of A Tire

There is a lot of information on the sidewall of a tire. Typically, you'll find UTQG ratings for treadwear, traction and temperature, the size of the tire, the load rating index number with a speed rating index, the construction type (bias or radial), the D.O.T. (Dept. of Transportation) compliance code, construction details, and of course, the make and model of the tire.

On some tires used as original equipment, you may also find a marking that indicates its OE status. Porsche uses an N-0 or N-1 designation, BMW uses a star on some O.E. tires and General Motors uses a "TPC" code.

There is a lot of information on the sidewall of a tire. Typically, you'll find UTQG ratings for treadwear, traction and temperature, the size of the tire, the load rating index number with a speed rating index, the construction type (bias or radial), the D.O.T. (Dept. of Transportation) compliance code, construction details, and of course, the make and model of the tire.

On some tires used as original equipment, you may also find a marking that indicates its OE status. Porsche uses an N-0 or N-1 designation, BMW uses a star on some O.E. tires and General Motors uses a "TPC" code.