Reasons to change your tyres

Modern tyres are very sturdy and can cope with most things. Punctures, though, can and do still happen. A tyre specialist should check your tyre after a puncture to decide whether it can be repaired.

What is a puncture?

Punctures are a result of sharp objects on the road e.g. screws, nails or glass which damage the tyre. As a consequence, the tyre could lose pressure. Should you notice that one or more of your tyres continuously loses pressure or you discover a screw or nail in the tread, you should visit your local tyre dealer as soon as possible to get your tyres checked.

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It's a good idea to check your tyres regularly for tyre wear. But how? Here’s a simple way to tell if your tyres are worn out.

Remaining tread depth

Tread wear indicators situated in each of the main grooves of the tread. These indicators are small raised areas at the bottom of the grooves of the tread pattern.

Tread wear indicators - Cross ribs evenly spaced around the circumference of the tyre in the main longitudinal tread grooves which become level with the tread surface when the remaining tread depth is down to approx. 1.6mm. Minimum tread depth standard at which tyres should be removed from service.

Manufacturers recommends the following tread depths for tyre replacement:

summer tyres 3 mm

winter tyres 4 mm

If the surface of the tread rubber is level with these raised areas, the tyre tread depth is most likely very close to the legal limit of 1.6 mm. Or below it! Manufacturers strongly recommends that you consider changing your tyres before this limit is reached. They may no longer provide sufficient safety and you could be breaking the law.

Even if the remaining tread depth is greater than 1.6 mm, you should adapt your speed and driving style to the external conditions, particularly on wet roads.

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Tyres have no predictable life. It doesn’t matter when the tyres were made. Tyres age even when not used, or if only used occasionally. There are many factors that will affect the life of the tyre such as temperature, maintenance, conditions of storage and use, load, speed, pressure as well as driving style. These will have a great impact on the length of service life you can expect from your tyres.

Pay regular attention to your tyres

Manufacturers recommends that all drivers pay regular attention to the external appearance of their tyres for clear signs of aging or fatigue. This can include cracking of the rubber or deformation, etc. Excessive aging of tyres may lead to loss of grip. Manufactures also recommends all tyres, including the spare, are inspected regularly by a tyre specialist. They can tell you whether your tyres should continue in service.

How old is too old? The five-year test

After five years or more in service, your tyres should be thoroughly inspected at least once per year. If the need arises, follow the recommendations of the vehicle manufacturer regarding replacing the original equipment tyres. As a precaution, if the tyres have not been replaced 10 years from their date of manufacture (see below how to read a tyre sidewall), Manufacturers recommends replacing them with new tyres. Even if they appear to be in usable condition and have not worn down to the tread wear indicator.

Tyre Age

The chronological age of any tyre can be found on the tyre sidewall by examining the characters following the symbol "DOT". The last four numbers identify the date of manufacture of the tyre to the nearest week. The first two of these four numbers identify the week of manufacture (which range from "01" to "53"). The last two numbers identify the year of manufacture (e.g., a tyre with the information "DOT XXXXXXX2714” was manufactured in the 27th week of 2014).

For tyres manufactured prior to the year 2000, three numbers instead of four indicate the date of manufacture. Also, during the early 1990’s, Continental added a triangle (?) to the end of the character string to distinguish a tyre built in the 1990’s from previous decades (e.g., a tyre with the information "DOT XXXXXXX274?” was manufactured in the 27th week of 1994).

We recommend: All tyres (including spare tyres) that were manufactured more than ten years ago should be replaced with new tyres, even if they appear to be usable from their external appearance and if the tread depth may have not reached the minimum wear out depth.

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Your tyre can be seriously damaged if it impacts any solid object on the road, like a kerb, pothole, or sharp object. Any visible perforation, cut or deformation must be checked thoroughly by a tyre professional. Only they can tell you whether the tyre can be repaired or has to be changed. Never use damaged tyres or tyres that have run flat or at very low pressures unless they have been thoroughly examined internally and externally by a tyre professional. Inspection by a professional is absolutely necessary because internal damage is not visible while the tyre is mounted; only then can a decision be made as to whether the tyre can be out back into service.

Tyre damages

Impact damage

What is a impact break / bulge?

An impact break involves damage to the carcass (the casing of the tyre) inflicted when the tyre is in contact with certain obstacles. Usually an externally visible bulge on the sidewall of the tyre indicates that cords have been destroyed inside the carcass. If such damage is ignored there is the risk of tyre failure at some time in the future, usually delamination of the tread and/or plies or disintegration of the tyre sidewall. Damage of this kind is typically caused by driving over objects – like kerbs or speed bumps – at excessive speed and/or at the wrong angle. This over-stress the carcass and can cause individual cords to break. The extent of the damage depends on the speed and angle of impact and on the size of the obstacle. Motorists are usually able to prevent this type of damage themselves. It is inevitable only in very exceptional cases - when an obstacle suddenly appears in front of a vehicle, for example.

Tip: Kerbs and similar obstacles should only be driven over at an obtuse angle and at appropriately slow speed.

Tyres can become damaged without the driver’s knowledge. Most common damages are punctures, cuts, impacts, cracks, bulges and irregular wear.

If you do discover or suspect damage, have the tyre inspected without delay by a tyre service professional.

Leave it to the experts

A tyre specialist will tell you if your tyre can be repaired after damage has occurred.

Cuts

Cuts are the result of external influences e.g. bad road conditions, protruding bodywork parts or sharp, foreign objects such as stones or glass. You should avoid driving aggressively on unpaved roads. If you discover cut damage on the tyre surface, you should visit your local tyre dealer and get your tyres checked by an expert immediately.

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Abnormal uneven tyre wear - in patches, in the centre, at the edges - may indicate a mechanical problem like improper wheel alignment, or a problem with wheel balance, suspension or transmission. It could also be that you're driving with the wrong tyre pressure. If you notice abnormal wear, contact your tyre specialist.

Irregular wear

There are several types of irregular wear. Most typical, one side wear, centre wear, braking flat spots. For all of them, there are different reasons how these kinds of wear occur.

To prevent uneven wear, have your wheels aligned and balanced by a tyre specialist. This will also extend tread life and give you a smoother ride. Another way to keep your tyre wear even is to regularly rotate your wheel positions.

Common causes of abnormal tyre wear:

• Wear on one shoulder: suspension misalignment.
• Wear on both shoulders: under-inflated tyre.
• Wear along the tyre's centre: over inflation.

The most frequent cause of one-sided wear is an axle geometry out of specification. These deviations develop over time and can be the consequence of, for example, kerb mounting.

Lowering a vehicle in conjunction with low-profile tyres can also negatively affect wheel alignment. The modified suspension arms (e.g. less rim offset after retrofitting) encourage a tendency for the alignment of the wheels to deviate during driving from the specified data. This might go unnoticed as all wheel alignment values are still found to be within tolerance limits when measured statically on the axle measurement bench. The result may be an increase in nonuniform wear.

The manufacturer’s alignment data applies to vehicles as delivered and may not necessarily apply to customised vehicles.

For best all-around performance, the same type of tyre should be used in all four-wheel positions. Tyres of different sizes, constructions, and stages of wear may affect vehicle handling and stability.

In addition, there may be specific recommendations by vehicle or tyre manufacturers which may apply to your vehicle. These should be followed, please check your vehicle handbook for details.

Never mix radial and non-radial tyres

The consumer plays an important role in tyre maintenance.

Consumers are strongly encouraged to be aware of their tyres visual condition. Also, they should be alert for any change in dynamic performance such as increased air loss, noise or vibration. Such changes could be an indicator that one or more of the tyres should be immediately removed from service to prevent a tyre disablement.

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