Current tread depth legislation requires that car tires must have a minimum of 1.6mm of tread in a continuous band throughout the central ¾ of the tread width and over the whole circumference of the tire.

To help drivers recognize when their tires are nearing the legal limit tires are manufactured with tread wear indicators in the grooves (pictured left).

However, despite the law, it is universally recognized in the tire industry that the legal limit is wholly insufficient to protect drivers in adverse driving conditions.

Drivers are therefore recommended to consider replacing their tires when the tread depth reaches 3mm.

Rib shape: Tread patterns dominated by multiple circumferential grooves -

Advantages include lower rolling resistance plus good directional stability and steering control thanks to lateral resistance. Rib type patterns are suitable for sustained high speeds thanks to their low levels of heat generation. Key disadvantages are poor braking & acceleration grip on wet roads. Application: For paved road surfaces and truck or bus steer axles.

Lug shape: Tread patterns with the groove arrangement perpendicular to the circumference of the tire -

The main advantage of lug patterns is excellent braking power and traction. The biggest disadvantage is a tendency towards high noise when driven at high speed. Indeed, lug patterns are not suitable for high speed driving due to their high rolling resistance. Application: For dirt roads, rear wheels of buses, industrial vehicles and dump trucks.

Rib-Lug shape: A combination of Rib and Lug designs -

Key features are a rib in the center providing directional control whilst a shoulder lug gives good braking & driving power. Application: Good for both paved and dirt roads. Usually used in both front & rear wheels of trucks and buses.

Block-shape: Patterns consisting of independent blocks divided by circumferential and lateral grooves -

Block patterns provide good steering control and stability on snow covered and wet roads as well as good water dispersal properties in the wet. However, because the tread blocks are smaller, tire wear tends to be heavy. Application: Suitable for winter or all-season passenger car tires as well as for the rear wheel use in ordinary applications.

Asymmetric pattern: Tread patterns which differ on either side of the tire -

Asymmetric tires have been designed to optimize the opposing requirements of dry grip and water dispersal. They are good for high speed cornering due to the greater contact area which helps reduce tread wear on the outside shoulder. Application: High performance and Motorsport tires.

Advantages of directional tread patterns are good driving force and braking performance. In particular directional patterns provide good water dispersal for greater stability on wet roads. Directional tires must be mounted in the direction of the tread pattern. Applications: Passenger car tire for high-speed use.

Uniform Tire Quality Grade(UTQG) -
A compulsory grading system for summer and all season tires sold in the United States. The UTQG provides comparative manufacturer information. Tires are subjected to a series of government tests that measure performance in treadwear, traction, and temperature resistance. All testing is done by the manufacturer. Due to this fact it is not accurate to compare the grading between brands. Each manufacturer uses different methods to obtain the grading hence differences in results will vary.

Temperature Resistance
This unit provides a measure of resistance to heat generation under normal operating conditions. The test is conducted under predetermined standards for inflation and loading. Excessive speed, under inflation, and overloading can all cause adverse heat build up. Sustained high temperatures can reduce tire durability. Resistance grades are branded on the sidewall.

• Resistance Grade A: The maximum performance level indicating the tire withstood a half hour run at 185 km/h (115 mph) without failing.

• Resistance Grade B: The tire passed 160 km/h (100 mph), but not 185 km/h (115mph).

• Resistance Grade C: The minimum performance level indicating that the tire failed to complete a half hour at 160 km/h (100mph).

Traction
Traction is a measurement of a tire's ability to stop in a straight line on wet test surfaces of asphalt and concrete. Traction grades are assigned by the UTQG system and branded on the sidewall.

• Traction Grade A: The tire performed well on both surfaces.

• Traction Grade B: The tire performed well on al least one of the two surfaces.

• Traction Grade C: The tire performed poorly on one or both of the two surfaces.

Up-Stepping by Fitting Low Profile Tires -

In order to attain the maximum performance out of your vehicle, larger and wider wheels are recommended. Although high performance is our goal, there are certain safety guidelines that must be observed. This means that wheel size and type, and tire height and width must fall within certain limits. When selecting a high performance tire the following must be observed.

Clearance Wheel well clearance must be maintained. Failure to do so would most likely severely cut the tire when turning, if not lead to a puncture. The vehicle manufacturer can provide the maximum tire width permissible. Otherwise consult a high performance tire dealer.

Wheel Selection
It is often the case that new wheels are required. This can be because either a larger rim width and/or larger rim diameter is called for. When choosing high performance wheels ensure that they have the correct offset and pitch circle diameter (P.C.D.) for your vehicle.

Up Stepping to High Performance
Maximizing your car's performance by selecting a lower profile tire/larger size rim combination is referred to as "up-stepping." Plus-one or plus-two tells you how much larger the rim size is. This "up-step" approach to improving performance came into being because, although it is possible to get higher performance without changing rims, it is often necessary to increase tire width to the point that steering geometry is affected, with the result that a change in driving style or habits becomes necessary.

So to fully maximize your vehicle's performance (which includes preserving the steering geometry) the "up-step" approach is highly recommended. By fitting a larger rim, increases in tire section width are properly managed while correct overall diameter is maintained. This maximizes cornering force and grip without sacrificing any other handling parameters.

Wheel Offset (Inset/outset) -
This is the distance in mm between the centerline of the wheel rim, and the line through the fixing face. You can have inset, outset or neither. This determines how the suspension and self-centering steering behave. The most obvious problem that will occur if you get it wrong is that the steering will either become so heavy that you can't turn the car, or so light that you need to spend all your time keeping your vehicle in a straight line. Other problems that can occur, include tires hitting the body or suspension and high speed vibrations in the steering wheel.

No offset	Inset wheel	Outset wheel