What Is an Out-of-Shape Tyre?

An out-of-shape tyre is one that no longer rotates evenly because part of its structure has distorted. The tread or casing may develop a high spot, bulge or uneven profile rather than remaining uniformly round.

What Symptoms Can It Cause?

A distorted tyre can cause a repeated vibration or shake that changes with road speed. If the problem is on a front wheel it may be felt more strongly through the steering wheel; a rear-wheel problem may be felt more through the seat or body of the vehicle.

Some tyre faults can also contribute to pulling or an unsettled feeling, but vibration and pulling can have many other causes, including wheel balance, wheel damage, suspension faults and alignment problems.

What Can Cause Tyre Distortion?

• Impact damage from potholes, kerbs or road debris.
• Internal belt or cord damage.
• Damage that allows moisture into the tyre structure.
• Operating the tyre severely underinflated or overloaded.
• Age, deterioration or manufacturing-related structural failure.

Is It Safe to Keep Driving?

A visible bulge, serious distortion, exposed cords or sudden unexplained vibration should be treated as a safety issue. Continuing to drive on a structurally damaged tyre can increase the risk of tyre failure.

Out of Shape vs Wheel Balance

An imbalance usually relates to uneven weight distribution in the rotating wheel and tyre assembly. An out-of-shape tyre is physically distorted. Both can cause vibration, so diagnosis should include inspection of the tyre and wheel rather than assuming balancing alone will fix the problem.