Tread wear indicator

Tire tread wear indicators are patterned ridges 1.6mm (0.0630in.) to 1.8mm (0.0709in.) higher than the rest of the tread surface, and are molded into the tread at four to six points along the circumference of the tire. As the tire tread wears in time, the depth of the ridges becomes less until they become flush with the surface of the tread. Tire tread wear indicators indicate the allowable limit of tire wear, showing when it is time to replace the tire. (3/5)

Unusual wear of a Tire

(1) Wear on tire shoulders or center If the tire inflation pressure is too low, the shoulders wear more faster than the center. Overloading produces the same effect. If the inflation pressure is too high, the center wear more faster than the shoulders.

(2) Inside or outside wear Cornering wear, shown in the left, is caused by cornering at excessive speeds. Deformation or excessive play in the suspension parts affects front wheel alignment, causing abnormal tire wear. If one side of the tire tread wears faster than the other, the main cause is probably incorrect camber.

(3) Toe-in or toe-out wear (Feathered wear) The main cause of feathered wear on the tire tread is defective toe-in adjustment. Excessive toe-in forces the tires to slip outwards and drags the tread’s contact surface inwards on the road surface, producing toe-in wear. The surface takes on a distinctive feather-like shape – shown in the illustration – that can be identified by running a finger across the tread from the inside to the outside of the tire. Excessive toe-out, on the other hand, producing the toe-out wear shown in the illustration.

(4) Toe-and-heel wear Toe-and-heel wear is partial wear that often appears on tires with lug and block tread patterns. Tires with a rib tread pattern wear to form wavelike patterns. Toe-and-heel wear tends to occur more easily when the tire is rotating and not being subjected to driving force or braking force. Therefore, toe-and-heel wear occurs most often in non-drive wheels that are not subjected to driving force. In the case of drive wheels, driving force causes tire wear in the direction opposite that of toe-and-heel wear. Braking force also produces similar results. As a result, there is normally little toe-and-heel wear in tires on drive wheels.

(5) Spot wear (Cupping) If the wheel bearings, ball joints, tie rod ends, etc. have excessive play, or if the spindle is bent, the tire will wobble at specific, points in its rotation at high speeds, applying strong friction of causing slippage, both of which lead to spot wear. A deformed or irregularly worn brake drum causes the brakes to be applied at regular intervals, leading to spot wear over a relatively wide area in the circumferential direction. HINT: A canvas patch applied to the tire tread to repair a puncture or a protrusion produced by separation will also lead to spot wear. Sudden starting, braking, and cornering may also lead to spot wear. An excessively unbalanced wheel assembly causes spot wear as well. (4/5)

5. Tire rotation

Because the load which is applied to the front and rear tires are different, and the level of wear also varies. Therefore tires should be rotated regularly so that they will wear uniformly. Tires which the rotational direction is determined must not be replaced at right and left. Tire which the tire size of front and rear are different must not be replaced at front and rear. As the recommended tire rotation method varies depending on model and region, refer to the Owner’s Manual.

1. Standing wave

When the vehicle is running, the tire continuously flexes as a new section of the tread comes into contact with the road surface. Later, when this section leaves the road surface, the pressure of the air inside the tire and the elasticity of the tire attempts to restore the tread and carcass to their original state. At higher vehicle speeds, however, the tire rotates too quickly to allow enough time for this. This process, continually repeated at such short intervals, gives rise to oscillations in the tread. These oscillations, which are referred to as standing waves, continuously propagate around the tire. The majority of the energy locked up in the standing waves is converted into heat, which sharply raises the tire temperature. Under certain circumstance, this heat build-up can even destroy the tire in the space of a few minutes by leading to separation of the tread from the carcass (blowout).

2. Hydroplaning

A vehicle skids on a water-covered road if the vehicle speed is too high to allow the tread enough time to remove the water from the road surface so that it can get a firm grip. The reason for this is that, as the vehicle speed increases, the resistance of the water increases accordingly, forcing the tires to “float” on the water’s surface. This phenomenon is known as hydroplaning or aquaplaning.

CAUTION:

Do not use a tire with a worn tread. As the tire wears, the tread reaches a point where the tread grooves cannot drain off the water between the tire and the road fast enough to prevent hydroplaning.

Raise the inflation pressure. A higher tire inflation pressure opposes the pressure of the water trying to force itself under the tread and thus delays the onset of hydroplaning.

3. Load

A higher load accelerates tire wear in much the same way as a reduction in inflation pressure does. The tire also wears more quickly during cornering when the vehicle is heavily loaded because the greater centrifugal force during cornering causes the vehicle to generate greater cornering force, thus generating greater friction between the tire and the road surface.

4. Vehicle speed

The driving and braking forces, the centrifugal force at cornering, and the other forces acting on the tire, increase in proportion to the square of the vehicle speed. Raising the vehicle speed therefore greatly multiplies these forces, increases the friction generated between the tread and the road surface, and thus accelerates tire wear. In addition to these factors, the condition of the road also has a great influence on tire wear: a rough road will obviously cause a tire to wear faster than a smooth road. (2/5)

Tire wear and braking distance

Tire wear does not greatly affect the braking distance on a dry road surface. On a wet road surface, however, the braking distance is considerably longer. Braking performance is poor because the tread pattern has worn down to the point where it cannot drain off the water between the tread and the road surface, leading to hydroplaning.