Truck and Bus Tyres

Section Height
---------------------   x 100 %
Section Width 

Measurement of the distance of an unladen tyre, from a tread surface to the tread surface on the opposite side of the tyre.

Measurement of the cross section of an unladen tyre, including ribs and protrusions. Usually the same as section width on radial tyres.

Measurement of the cross section of an unladen tyre across the casing only, not including ribs or protrusions.

Distance across the tread face of an unladen tyre.

Distance from the tread surface to the major groove base at a designated measuring point.

Distance from the bead seat to the tread surface of an unladen tyre.

Distance between the rim flanges.

Diameter of the rim from bead seat to bead seat in inches.

Distance from the centre of the axle to the ground of a loaded tyre, under maximum dual load and inflation pressure.

The maximum section width of a loaded tyre, under maximum dual load and inflation pressure.

The minimum allowable distance between the wheel centre lines in a dual arrangement.

The number of tyre revolutions in one kilometre, measured at: 100km/h, maximum dual load and inflation pressure.
Note: All dimensions are measured following a 24-hour inflation period.

Dual tyre assemblies are commonly used on drive and trailer axles, however, they do require attention if tyre life is to be maximised.

Diameter Variations
Dual assemblies with significantly different diameters will produce suboptimal wear results for both tyres. The tyre with the larger diameter will carry more of the load, causing rapid wear. The tyre with the smaller diameter will be subjected to very high levels of slip, creating rapid and irregular wear.

Pressure Differentials
When tyres in a dual assembly are inflated to different pressures they will produce suboptimal wear results for both tyres. The tyre with the higher inflation pressure will have a higher contact pressure with the road and carry more of the load, causing rapid wear. The tyre with the lower inflation pressure will have a lower contact pressure with the road, resulting in rapid and irregular wear.

Recommendations
Bridgestone recommends that the same brand, pattern, size, load index and speed symbol be used when matching duals. The following upper matching limits for dual tyres should also be observed: 

A vehicle’s wheel alignment can have a dramatic effect on how evenly and quickly the tyres wear. The following diagrams illustrate the most important areas of wheel alignment.

Typical Alignment Settings*

* All vehicles and operations are different, thus no one alignment setting can cover the range entirely. Typical alignment settings for prime movers operating in line haul applications have been provided. Please consult an alignment professional for settings for specific operations

Load and Inflation Pressure
It is the air inside your tyre that carries your vehicle’s load. As a result, lowering the inflation pressure is equivalent to increasing the load on the tyre. 

The maximum cold inflation pressure for Australia is 825kPa (120psi) which we have accounted for, while the maximum cold inflation pressure allowed in New Zealand is 900kPa (130psi).

Recommended Pressure
The correct inflation pressure will depend on tyre size, service description, actual load, actual speed, fitment, and operating conditions. In addition, tyres in a dual configuration will be able to carry less load per tyre because of unqeual loading conditions, and thus must be inflated differently. Incorrect inflation pressure can result in irregular wear, reduce wear life, damage, or even tyre failure.

Inflation pressures should be checked on cold tyres at least every month, using a reliable pressure gauge. Always use a sealing type valve cap and don’t rely on the valve core seal, as it is only secondary.

Tyre rotation is a practical means of reducing operating costs by helping to overcome irregular wear patterns, and minimising the effects of different wear rates. Rotation can ensure that a tyre’s tread is fully utilised—reducing the cost per kilometre.

In some cases the driver’s side steer tyre on a prime mover can wear one half of the circumference of the tyre more than the other half. This creates a light point, which unbalances the tyre and causes vibration. By rotating steer tyres regularly, this effect is minimised and steer tyre vibration is usually prevented.

Tyres should be rotated to the positions shown in the diagrams. Note that dual pairs should be rotated in the same pairing, ie. outside tyre remains on the outside, but in the new position.

Steer Tyres: 25,000km
Drive Tyres: 50,000km
Otherwise, rotate as often as required to minimise irregular wear or vibration.

If the application allows, steer tyres can be rotated onto the drive and trailer axles and drive tyres can be rotated onto the trailer axle.

The table below outlines some common types of irregular wear and some typical causes.

Image tile	Appearance	Causes
	Shoulder Edge Wear Even wear in centre but shoulder wearing rapidly. Note: Often results in little or no loss of removal mileage	Incorrect toe; Drive axle misalignment; Worn suspension; Incorrect camber
	River Wear Circumferential wear along rib edges. Common on free rolling axles. Note: Often a sign of a tyre achieving good mileage	Light loading; Excessive turning; Worn suspension; Assembly lateral runout
	Heel/Toe Wear Each block worn high to low from front to back.	Mismatched duals; Incorrect inflation pressure; High traction operating conditions; Lack of rotation
	Feather Wear One side of each rib is worn. Note: Often seen on both steer tyres	Excessive toe; Drive axle misalignment; Bent tie rod or chassis; Worn suspension
	Diagonal Wear Localised flat spots worn diagonally across the tread.	Mismatched duals; Underinflation; Radial runout; Excessive imbalance; Misalignment; Other wear condition; Loose wheel bearings
	Rib punch wear One or more of the inner ribs is worn.	Incorrect inflation pressure; Poor shock absorbers; Worn wheel bearings; High speed empty hauls; Excessive imbalance
	Block punch Alternate blocks worn different amounts.	Mismatched duals; Incorrect inflation pressure; Axle misalignment; Large variation in loads; Worn suspension; Lack of rotation
	Island wear Small ‘islands’ of tread are less worn.	Assembly imbalance; Incorrect inflation pressure; Worn suspension; Mismatched duals; Misalignment

Tyres being stored should be kept away from direct sunlight, heat sources, ozone creating generators, motors and welders, moisture, dirt, oils and chemicals in order to prevent the tyre from degrading.

Wheel nuts should be assembled in the sequence recommended by the vehicle manufacturer. Furthermore, wheel nuts must be checked within 50km of fitment. Torque levels and sequences are recommended by the vehicle manufacturer. Always use a torque bar to tighten wheel nuts.

Ignoring tyre damage is dangerous. Damaged tyres must be assessed and repaired by a qualified Bridgestone mechanic as soon as possible, in order to avoid further deterioration of the tyre structure.

Any new tyre or tube manufactured by Bridgestone is guaranteed to be free of material and manufacturing defects. Should any such tyre or tube develop a material or manufacturing defect, Bridgestone will make a pro-rata allowance towards the purchase of a new tube or tyre.