Maintaining the tyre balance on your vehicle is critical to long term durability of the tyres and the overall performance and safety of your vehicle. When the wheel rotates, asymmetries in its mass distribution can apply periodic forces and torques to the axle, creating a rougher ride (such as experiencing vibrations and an oscillating steering wheel).
The frequency and magnitude of disturbance to your ride usually increases with speed and when the rotating frequency of the wheel is equivalent to the resonant frequency of the suspension. Vibrations can occur due to tyre imbalance or because of wheel unbalance, imperfect tyre or wheel shape, problems with suspension, brake pulsation and worn or loose driveline or steering components.
WHY TYRE BALANCE IS IMPORTANT
As the technology in vehicles have advanced, precision has become increasingly important. Heavier vehicles in the past could smooth out and dampen vibrations thanks to their weight and softer suspension so the driver couldn’t feel them. Today, cars are much lighter and faster than they once were, meaning we can feel bumps and vibrations more while driving.
More responsive tyres with lower profiles are more common in tyre technology today as they provide the driver with more feedback about the road, provides lower rolling resistance, helps with fuel economy and better suits today’s performance and style orientated market. The result is that the slightest imbalance in tyres can be felt in most modern cars.
STATIC VS DYNAMIC BALANCING
Static imbalance occurs when there is a light spot or heavy spot in the tyre that causes it to roll unevenly. This causes the wheel to undergo an up-and-down motion. This creates a hop or vertical vibration. Dynamic imbalance is when there is an uneven distribution of weight on one or both sides of the assembly’s lateral centre This causes a side-to-side vibration or wobble.
Most assemblies will experience both types of imbalance and require dynamic balancing (also called spin balancing) to correct it and even out the weight distribution. This involves placing counter weights on the outer surface of rims to offset the imbalance. When the balancing system tests for an almost perfect weight distribution, the assembly is in balance and will no longer vibrate. Your tyres will then provide a smooth ride and wear evenly.
HOW DO TYRES GET IMBALANCED?
When tyres are mounted onto wheels, the completed assembly weighs around 18 kg. It is almost impossible for this assembly to have 100 per cent precision in weight distribution about its radial and lateral centres. All it takes is 14 grams of uneven weight distribution for vibrations to be felt.
Keeping your tyres balanced is about making incremental adjustments after test driving and monitoring tyre tread. This is an ongoing task as turning, hitting bumps and holes and driving down uneven road surfaces can all create or escalate tyre imbalance.