What is tyre bulge?

A tyre bulge, commonly referred to as a bulge in tyre, is an issue that shouldn't be ignored.

This noticeable protrusion on the sidewall or tread of your tyre usually means there is some form of internal damage, such as a break in the inner layers or cords. Various factors can cause tyre bulges: riding over one too many potholes or curbs, manufacturing or age-related defects, or excessive wear.

It’s important that you address a bulge in a tyre promptly, because it can compromise your vehicle's safety and can lead to bigger problems such as sudden tyre deflation.

What does a bulge in your tyre mean and how do you fix it?

A bulge in your tyre means that the inside of the tyre is damaged. This damage creates a weak spot that causes an air bubble or bump to form on the tyre's surface.

What causes tyre bulge?

Think of your tyre like a strong balloon. When it's in good shape, it stays firm and works well. But if you press one side too hard, put too much air in it, or if there's a weak spot, it will bulge out and lose its strength. The same thing happens with your tyre.

Tyres get their shape and strength from plies and cords made of metal or fabric, which are integrated into the rubber during construction. These plies and cords keep the wall of a tyre firm and helps to prevent damage from the impact of brushing a curb or hitting a pothole.

When the cords break, the rubber sidewall can't contain the internal. As the air forces its way out, it gets trapped by the outer rubber layer, leading to a bulge. Learn more about how air pressure can affect your tyres.

Let's take a closer look at the different causes of tyre bulge and how you can identify them:

• Damaged cords – The inner cords of the tyre are important for maintaining its shape and strength. When these cords are damaged, it weakens the tyre's structure, causing a bulge.
• Driving at excessive speeds – High speeds can generate excessive heat and stress on the tyre, leading to internal damage and lead to bulges forming.
• Hitting obstacles or potholes – Impact from hitting potholes, curbs, or other things on the road can cause immediate damage to the tyre's structure, resulting in a bulge.
• Overstressing the tyre structure – Overloading your vehicle or driving on under-inflated tyres puts extra stress on the tyre's structure, which can lead to the formation of bulges.
• Tyre age – Over time, tyres wear down, so it's important to check them for signs of wear and tear. Tyres have a special code on their side that tells you how old they are. Look for a four-digit number inside a small box near the letters "DOT." The first two numbers show the week, and the last two numbers show the year the tyre was made (for example, "2319" means the tyre was made in the 23rd week of 2019).

How can I fix a bulging tyre?

Tyre bulges are dangerous and cause serious structural damage to a tyre, which means it can’t be repaired and must be replaced immediately. Driving with a bulging tyre increases the risk of sudden failure, which again is dangerous. For this reason, it's important to prioritise routine check-ups at a professional tyre shop or automotive service centre to have the damaged tyre inspected and replaced.

Will a bulge in my tyre affect my MOT?

Tyre bulges are a significant safety risk. Since the MOT is primarily a road safety check, a tyre bulge will lead to your car failing its MOT. When you’re getting your car ready for its MOT, remember that tyres can develop bulges on their inner sidewalls, not just the more visible exterior surfaces. It's crucial to inspect all parts of your tyres to make sure they’re road safe and won’t impact your MOT.

How dangerous are tyre bulges?

Though tyre bulges are common, their occurrence is no less dangerous. The most significant danger associated with tyre bulges is a blowout. When the sidewall's internal structure is compromised, the tyre becomes prone to sudden deflation. This can happen while driving, leading to a loss of vehicle control and potentially causing a serious accident.

In addition to the blowout risk, a bulging tyre can lead to other problems, such as reduced traction and uneven wear. Loss of traction over time due to wear means your tyre struggles to grip the road, especially in wet or icy conditions.

Is a bulging tyre illegal?

Driving with a bulging tyre is not only unsafe but also illegal. According to the Highway Code, tyres must be in good condition to ensure road safety. Specifically, Rule 97* states that your tyres should be "correctly inflated to the vehicle manufacturer's specification" and "free from any defects which might cause a safety risk." A bulge in a tyre is considered a serious defect as it indicates internal damage and a compromised tyre structure.

How can I avoid tyre bulges?

While some wear and tear or manufacturer defects are unavoidable, you can easily improve your driving habits and stay on top of regular car maintenance to mitigate these issues.

Keep your tyres in top condition for a smooth and safe driving experience with these practical steps to help you avoid tyre bulges:

• Avoid potholes and road hazards as much as possible.
• Drive cautiously. Sudden stops, sharp turns, and high speeds put extra stress on your tyres, increasing the risk of bulges. 
• Regularly check and rotate your tyres where possible.
• Invest in quality tyres because they’re built to withstand more stress and generally last longer.
• Avoid overloading your vehicle. Carrying too much weight puts extra pressure on your tyres, increasing the risk of damage. Always adhere to your vehicle's recommended load limits to prevent overstressing your tyres.
• Regularly check your tyres.

Want more advice about your bulge?

If you need more guidance on dealing with tyre bulges or any other related issues, our experts are here to help with breakdown cover. Stay safe on the road and ensure your vehicle is in top condition.