Tyre Safety Guide & FAQs

If you’re driving on illegal tyres you could invalidate your insurance policy and if you’re below the legal tread, you could face a hefty fine. Worn tyres are going to significantly affect your vehicle's performance as they reduce the effectiveness of steering, braking, and accelerating which are all important features to keep you safe on the road. Here at Donnelly Group Tyre Services, we are committed to tyre safety which is why we have put together a handy guide to make sure your tyre safety questions are answered.


How to read tyre labels to find the correct tyre size

The size of your tyre is printed on the sidewall, when looking for the size you will see that it’s made up of a series of letters and numbers. Here is an example of what you might see:

205/55 R 16 91 V

  • 205 = Tyre Width represents the tyre’s width in millimetres, sidewall to sidewall.
  • 55 = Aspect Ratio represents the measurement of the height of the sidewall in millimetres.
  • R = Tyre Construction tells you how a tyre is constructed, in this example, the tyre has radial construction.
  • 16 = Rim Diameter is shown in inches and represents the diameter of the wheel rim, in this case, the 16 means the tyre should be matched to a wheel rim of 16 inches.
  • 91 = Load Index is the maximum capacity of a passenger car tyre when it's inflated to the maximum safe pressure.
  • V = Speed Rating Index is the final marking and denotes the maximum speed the tyre can sustain when it’s correctly inflated and under load.

Why is tyre pressure important?

Tyres don’t have to look flat to be underinflated, so to be sure your tyres are at the correct pressure you need to check them regularly. We would recommend checking pressures once every two weeks and you can find the correct tyre pressure for your car in your vehicle’s manual. Here are a few reasons why tyre pressure is important:


As vehicles frequently carry heavy loads, tyres must be inflated to the correct pressure. If a tyre is under-inflated excess heat builds up within a tyre, which greatly increases the likelihood of rapid deflation.

This is a major safety risk as it can cause loss of control and can also put other road users at risk. Overinflated tyres can also have major safety implications as it makes them more vulnerable to damage.

Vehicle Handling

Tyres are engineered to work in harmony with the vehicle's braking, steering, and suspension systems. If a tyre is under-inflated it contains insufficient air to support the weight of the vehicle. This can greatly affect acceleration, braking, and cornering, potentially making unsafe driving.

Fuel Economy

By keeping tyres properly inflated, drivers can travel further on each tank of fuel and reduce their CO2 emissions.

Premature Tyre Wear

A vehicle's load is supported in the shoulder area of the tread, therefore under-inflated vehicles experience rapid wear in this area. Driving on overinflated tyres results in higher wear in the centre of the tread. Keeping tyres inflated to the recommended pressure for the vehicle and load ensures a even wear rate, helping the tyres last longer.

How do I check my tyre pressure?

As the only contact your vehicle makes with the road at all times, your tyres put up with A LOT. Yet, when it comes to checking tyre pressures - it's something many motorists put off. Now that you know poorly maintained tyres can lead to serious safety implications, it's vital you take care of them. To make it easier for you, here's how you can check your pressure in a few simple steps:

- You can find the required pressures for your van or car in the vehicle manufacturer's handbook. Be sure to check the pressure when tyres are cold or when the vehicle has travelled less than two miles to get the most accurate reading.

- Remove the dust cap and press the gauge firmly on the tyre valve system

- Check the reading on the pressure gauge to decide whether or not to deflate or inflate your tyres.

- If your tyres need to be inflated, be sure to only add small amounts of air at a time to avoid overinflation. If your tyres need deflating, you can use the tip of a flat head screwdriver to push on the metal pin on the valve to release air.

Make sure to check all four tyres as the pressure can vary significantly! Also check your spare tyre as well, as you never know when you're going to need it!

When checking tyre pressures, it’s advised to give the rest of the tyre a thorough visual inspection. Remove any stones and other objects embedded in the tread. Look out for any cuts, lumps or bulges.

If you are unsure on any aspect of tyre pressure or tyre condition take your vehicle to an approved fitting centre like Donnelly Group Tyre services and speak to our experts, we offer a complimentary tyre check!

What is the minimum legal tyre tread depth?

Current UK law requires that the tyres must have a minimum depth of 1.6 millimetres, across the central ¾ of the tread around the complete circumference of the tyre. Drivers found in breach of this could face 3 penalty points and a £2,500 fine. Adequate tyre tread depth is vital for vehicle safety. Insufficient tread depth can extend stopping distances even further in wet conditions.

At Donnelly Group Tyre Services, we would recommend considering changing your tyres when they reach a minimum of 3mm. Tyre tread makes up the grooves and ridges that run along the circumference of a tyre’s rubber surface, they offer grip to the road surface allowing you to brake and manoeuvre safely. As tread depth decreases, the tyre’s performance deteriorates making it more difficult to transmit traction to the road effectively.

How do I check tyre tread depth?

One of the easiest methods for checking tyre tread depth is by using a 20p coin:

- Take your 20p coin and insert it into the tread grooves on your tyres.

- If you can't see the outer band of the coin, your tyres are above the legal limit.

- If it's still visible, your tyres could be below the legal tread limit and should be checked immediately by a qualified tyre professional.

- Check the tread at a few different points on the tyre to identify whether or not there is uneven wear.

We recommend you conduct the 20p test at least once every month, particularly before setting off on long journeys.

Does wheel alignment affect tyre wear?

Wheel alignment has been designed to minimise tyre wear and maximise driving comfort, when your wheels are correctly aligned, this will reduce wear and increase the lifespan of your tyres, as well as performance and fuel economy. So when your wheels are misaligned, your tyres are going to wear unevenly and it will significantly reduce the lifespan. Wheel alignment also plays a part in improving how your car handles as it reduces any steering and stability problems that may come from tyre alignment being off.

If you’re unsure as to whether or not your alignment is off, there are a few tell-tale signs you can look out for such as your vehicle pulling sharply to one side when travelling on a straight, flat road with no wind or if there is irregular wear on your tyres. You may even have squealing or noisy tyres if your wheels are misaligned. Wheels can become misaligned when hitting something such as a curb or pothole, or when if you have had steering or suspension components replaced recently.

How long should my tyres last?

There is really no way to tell how long a tyre is going to last because the lifespan and mileage of a tyre is going to depend on many different factors such as design, quality, driving habits, road conditions, and how well you look after them. However, if you have had the same tyres on your car for longer than five years, it’s best to have them inspected by a professional.

What is a run-flat tyre?

Run-flat tyres are designed to continue to be driven at reduced speeds for a short time after a puncture or other form of deflation. Run-flat tyres are built with reinforced sidewalls, with tough rubber inserts to help temporarily hold up the weight of your vehicle even after a puncture.

When your run-flat tyre suffers a puncture, it doesn’t mean you can keep driving on it forever, usually, you will get another 50 miles out of the car at 30 miles per hour, but the exact range is going to depend on things like your driving speed, the load of the vehicle you’re driving and the driving conditions.

There are a few advantages to having run-flat tyres such as not having to change your tyre in dangerous or awkward conditions, they are more stable when punctured unlike conventional tyres, and can help you maintain better control in a complete air loss situation.

Can my punctured tyre be repaired?

If you have punctured your tyre, you might be wondering whether you need to completely replace the tyre or if you can repair it. While you might be able to repair it in a few cases, it’s not always going to be possible. With that in mind, here are a few cases of when tyres can and cannot be repaired:

  • Puncture Location: Punctures can only be repaired if they occur in the central portion of the tyre. It if occurs too near to the sidewall, generally it cannot be repaired because this part of the tyre carries the largest load when driving.
  • Run-Flat Tyres: Unfortunately, run-flat tyres cannot be repaired, only driven on for a short time after a puncture. So while this is a huge benefit, it’s not possible to tell whether the structure has been damaged during or after the puncture and this will result in the tyre needing to be replaced.
  • Puncture Size: If the size of the damaged area is bigger than the maximum area stipulated by British Standard BSAU159, you should not have the tyre but replaced instead. Small punctures caused by driving over nails or something of a similar size that’s sharp can often be repaired because the damaged area is so small.
  • Tyre Condition: Before a repair is carried out, any reputable tyre technician will check the condition of the tyre before attempting to repair it, such as whether or not the tyre is less than the legal limit.

I’m on the Motability scheme, can you replace my tyres?

Yes, if you’re on the Motability scheme and need to have your tyres replaced or repaired, you can visit your nearest Donnelly Group Tyre Services location and we can help get you back on the road as quickly as possible!

I operate vans as part of my business. What do I need to take into consideration?

Equally, Van drivers and business owners have a duty of care to ensure vans and light commercial vehicles remain safe and legal. Carrying heavy loads or doing multiple drops in tough working environments can cause levels of damage beyond that of a car tyre.

Since The Health and Safety Offences Act of 2009 business owners must ensure that they must carry out regular checks on vans to remain safe and legal. UK courts have greater authority to prosecute businesses and fine a maximum of £20,000 and individual drivers up to £2,500 and three penalty points for each illegal tyre.

If you believe you have been sold a part-worn tyre that does not comply with existing legislation please contact your local Trading Standards Office. Donnelly Group Tyre Services is a member of The National Tyre Distributors Association, which is a strongly proactive trade association representing and promoting the interests of the tyre wholesale, distribution, and retail sectors of the automotive aftermarket industry.

How do I know which tyres are best?

If you’re unsure as to which tyres are going to be best for your car and van, you can talk to our experts! As a family-run business, tyre safety is extremely important to us, and we only stock tyres from leading manufacturers including Continental, Uniroyal, Yokohama, Alliance, Toyo, Goodyear, Dunlop, BFG, Pirelli, Hankook, Nexen, Bridgestone, and Kuhmo. To find out more about how Donnelly Group Tyre Services and to request a quote for your vehicle click Enquire Now below or search for your nearest dealership.

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