Repairing A Car Tyre Puncture – When And When Not To

Repairing a car tyre puncture is less expensive than replacing the tyre as a whole. While a new tyre can range between £50-£150, patching the hole can run you as little as £20-30. This could put you back on the road after a short visit to a repair shop like Autofusion, allowing your tyre to continue for thousands of miles in good condition.

However, not all puncture marks are possible (or safe) to patch. It will depend on the:

• Overall condition of the tyre
• Location of the puncture mark
• Size of the damaged area
• How long the tyre has been punctured

Some tyres will be too heavily damaged to repair, or they are punctured in a location that can't be safely patched. Trying to do so could lead to a tyre that won't inflate, at best. At worst, it could risk your safety on the road and the overall lifespan of your car.

A mechanic will be able to assess what's best for your particular tyre, but it helps to know what to expect. Can your punctured tyre be repaired, or will a new tyre be needed?

Where Is The Location Of The Puncture?

In the U.K., the process of repairing a punctured tyre must adhere to British standard (BSAU159). This standard defines the requirements for safe, minor repairs on tyres – and, most importantly, their proximity to the tyre's sidewall.

To remain compliant, shops like Autofusion can only carry out repairs on the middle portion of a tyre's tread, within an area of 60-70% of the tyre's width. This is known as the "minor repair area", whereas that 30-40% of tread near the sidewalls is considered a "major repair area". If the puncture is situated closer to the sidewall, even in the case of a slow puncture, it's deemed as too close to the sidewall to guarantee a safe and lasting minor repair.

Why Can't A Tyre Sidewall Puncture Be Patched?

The sidewall is the load-bearing area of a tyre. It not only supports the vehicle itself, but anything placed within it. Trying to patch this area would compromise its overall strength and durability. This could lead to a patch that doesn't stick (at the least) or a collapsed sidewall (at the worst).

Furthermore, when a punctured tyre is repaired, the damaged area is prepared using an air drill. This is perfectly safe when used on the central tread, but the sidewall also endures the most flex in the tyre. This means any patch applied to this area is far more likely to detach as a result of the increased movement, leading to tyre failure.

How Long Has The Tyre Been Punctured?

A newly punctured tyre is far easier to patch. If you keep driving on a flat tyre, however, then you risk damaging the tyre overall. Without the air pressure to keep its shape, the tyre sidewall will be pinched between the wheel rim and the road when in motion, deforming it.

So, even if your puncture is located in the minor repair area, if you drive on the deflated tyre, it may not be repairable, thanks to additional damage sustained to the tyre sidewall.

What Is The Size Of The Damaged Area?

Depending on the extent of the damage, even a puncture mark in the minor repair area could be impossible to fix. British standard also defines the maximum size of the damaged area in order to carry out a safe repair.

If the diameter of the damaged area is larger than 6mm, a repair should not be attempted. This means it may be possible to repair a tyre that has been pierced by a nail or a screw, but if the damage is caused by a larger item, such as a bolt or other metallic debris, the tyre may need to be replaced. This also means that splits, cuts, and gouges cannot be repaired.

What Is The Condition Of The Tyre?

Before repairing a punctured tyre, a mechanic will evaluate the general condition of the tyre to make sure that it's fit for repair. The legal limit for tyre tread in the U.K. is 1.6mm across the central "minor repair area" of the tyre.

If the remaining tread is less than this, or the sidewall exhibits bulging or exposed cords, then a repair will not be attempted. The tyre itself is no longer road-safe, and trying to fix a worn-out tyre is likely to weaken it further or cause a blowout.

Not only is it against the law to drive a vehicle with tyres below the legal limit; it's also a major safety risk.

Repairing A Car Tyre Puncture – Should I?

It's possible and safe to repair a punctured car tyre if the:

• Tyre is in good condition
• Damaged area is merely a small puncture (like with a nail)
• Puncture site is within the U.K. legal limits of a "minor repair area"
• Repairs are carried out soon, before the damage escalates or the sidewall becomes deformed

If you are looking for a tyre puncture repair, or have concerns about the general condition of your tyres, book a free tyre safety check with Autofusion. Our experts can help patch your tyre or provide any servicing needed if your tyre can't be safely repaired.