The Customer’s Description of the Problem

When the vehicle arrived at e-CAR Menlyn, the customer described the problem like this:

“The car drives normally in town, but it starts shaking when I reach about 100 km/h. The faster I go, the worse it becomes.”

That description gave us several useful clues:

• The vibration was related to vehicle speed
• It appeared within a particular speed range
• It was present without applying the brakes
• It was felt mainly through the steering wheel
• The engine appeared to run normally
• The car did not vibrate while stationary

These details made a wheel, tyre, steering or suspension problem more likely than an engine problem.

However, a symptom alone cannot confirm which component is responsible.

Was It Just Wheel Balancing?

Wheel imbalance is one of the most common causes of a vibration that appears at higher speeds.

A wheel may become unbalanced when:

• A balancing weight falls off
• A tyre wears unevenly
• A tyre is replaced without balancing the wheel
• Mud or debris collects inside the rim
• A wheel is damaged by a pothole
• The tyre or rim no longer rotates evenly

But balancing is not the only possibility.

Similar symptoms can be caused by:

• A damaged or distorted tyre
• A bent wheel rim
• Uneven tyre wear
• Incorrect tyre pressure
• Worn suspension components
• Worn steering components
• A wheel-bearing problem
• A damaged CV joint or driveshaft
• Incorrect wheel alignment

This is why simply balancing the wheels without inspecting the tyres and suspension can miss the actual problem.

What We Checked

We started with a visual inspection of the wheels and tyres.

The tyre pressures were checked, and we examined the tread for uneven wear, flat spots, cuts, bulges and other visible damage. We also checked that the wheels were correctly fitted and that there was no obvious movement in the steering or suspension.

At first glance, the front tyre did not look severely damaged. It still had tread remaining, and there was no large puncture or obvious cut in the sidewall.

The problem became clearer when the wheel was rotated and checked on the balancing equipment.

Instead of rotating evenly, the tyre showed a slight variation in its shape. Part of the tread moved up and down as the wheel turned. The wheel was also out of balance, but adding more balancing weights would not have corrected the underlying tyre problem.

The tyre had developed an internal structural fault and was no longer running true.

What Was Causing the Vibration?

The high-speed vibration was being caused by a distorted front tyre.

At lower speeds, the distortion was not strong enough for the driver to notice. As the vehicle’s speed increased, the uneven rotation created a repeated movement that could be felt through the steering wheel and the front of the car.

This is why the vibration appeared at approximately 100 km/h and became worse as the vehicle travelled faster.

The wheel imbalance contributed to the shaking, but the tyre itself was the more important problem.

Balancing a damaged tyre may reduce a vibration temporarily, but it cannot repair the internal structure of the tyre.

Why the Tyre Problem Was Easy to Miss

Not every damaged tyre looks flat or badly worn.

A tyre can appear reasonably normal while fitted to the vehicle. Internal damage, tread distortion or belt separation may only become noticeable when the wheel is lifted and rotated.

Possible causes of this type of damage include:

• Striking a pothole
• Driving with incorrect tyre pressure
• Previous impact damage
• Age-related deterioration
• Heat and prolonged use
• A manufacturing defect
• Damage caused by driving on an underinflated tyre

The customer could not recall one specific incident that caused the problem. This is not unusual. Tyre damage can develop gradually after an impact and only become noticeable later.

The Repair

Because the tyre was structurally damaged, replacement was the appropriate solution.

After the tyre was replaced, the wheel was balanced correctly and the remaining wheels and tyres were checked. The steering and suspension inspection did not reveal another fault responsible for the vibration.

The vehicle was then road-tested again.

The vibration that had previously appeared at approximately 100 km/h was no longer present, and the vehicle remained stable as its speed increased within the legal limit.

What Could Have Happened If It Was Ignored?

A vibration is not only an irritation. It is the vehicle telling you that something is not rotating, supporting or moving as it should.

Continuing to drive with a damaged tyre can result in:

• The vibration becoming progressively worse
• Accelerated or uneven tyre wear
• Reduced stability
• Additional strain on steering and suspension components
• Poorer contact between the tyre and road
• An increased risk of tyre failure

Turning up the radio or becoming accustomed to the vibration does not make the underlying problem disappear.

If a vibration begins suddenly or becomes severe, reduce your speed safely and arrange an inspection. Do not continue testing the problem by repeatedly driving at higher speeds.

Not Every High-Speed Vibration Has the Same Cause

In this case, the main problem was a distorted tyre. Another vehicle with an almost identical symptom could have a different fault.

Where you feel the vibration can sometimes provide a clue:

• Steering-wheel vibration: Often associated with front wheels, tyres, steering or front suspension
• Vibration through the seat or floor: May originate from the rear wheels, tyres or drivetrain
• Vibration only when braking: May be associated with brake discs, hubs, suspension or braking components
• Vibration when accelerating: May involve engine mountings, CV joints, driveshafts or drivetrain components
• Vibration at most speeds: May indicate more substantial tyre, wheel, bearing, suspension or drivetrain problems

These are possibilities, not a diagnosis. The vehicle must be inspected to find the actual cause.

What Should You Tell the Workshop?

A clear description can make fault-finding easier. Try to explain:

• At what speed the vibration begins
• Where in the car you feel it
• Whether it happens while accelerating
• Whether it happens when braking
• Whether it changes when turning
• Whether it started after hitting a pothole
• Whether tyres or suspension parts were recently replaced
• Whether the problem is constant or intermittent

You do not need to know the name of the faulty part. Tell us what the vehicle is doing, and we can inspect it.