All You Need to Know About Tyres
A Guide by First Aid Wheels
This comprehensive tyre guide delves into a number of practical topics, such as how to change a tyre, check tyre pressure and tread, what is the legal tyre tread and why is tyre rotation so important. There’s also plenty of tyre maintenance tips for motorists, so read on to see how you can get the best out of your tyres for the longest possible time.
The importance of car tyres comes down to logic as simple as this: without a good set of them, you won’t go too far. Those black circles around your wheels keep the vehicle in motion and need to be treated right, because if they’re faulty, your car could suddenly come to a halt and you’ll be left stranded.
Functions of Tyres
Your car’s tyres are essential components of the vehicle and these rubber circles act as the intermediary between your vehicle and the road. Your tyres perform several vital functions:
They support the weight of the vehicle, as well as the people and objects within it.
They transfer torque, traction and braking forces to the surface of the road.
They perform an essential cushioning function by absorbing rod shocks.
They provide a stable response to changes in the car’s direction resulting from your steering.
Types of Tyres
Summer tyres: Warm, sunny weather is the easiest in which to drive, and summer tyres usually come with a simple block-shape tread pattern to ensure rigid contact with the road, maximising the friction between tyre and road surface for optimum grip.
Winter tyres: In stark contrast to ideal summer conditions, the snow and ice of the winter months can make driving extremely hazardous. Specially-manufactured winter tyres come with added grip to improve car control and braking performance on icy roads, thanks to the deep, wide grooves which provide increased traction.
All-season tyres: For motorists fortunate enough to live in an area where extreme weather conditions are rare, a good economical option is to fit all-season tyres on your car. However, they do not perform as optimally as season-specific summer or winter tyres, and if roads are very icy, they may not provide sufficient grip, even with the good traction they offer.
Wet weather tyres: Wet roads can be dangerous, especially if heavy rain follows a long dry spell where roads could become oily and slippery. Wet weather tyres come with a larger than usual tread depth (it should always be at least 1.6mm) to expel the rain away from where the tyre is in contact with the road. A larger tyre depth increases the tyre’s ability to evacuate water.
High-performance tyres: These are manufactured chiefly for luxury and sports cars. They are softer and grip better than regular tyres and they are also better for cornering, but they have a rather short lifespan and, in wet conditions, they cannot dissipate water as quickly as normal tyres.
All-terrain tyres: Also known as off-road tyres, these can operate smoothly on regular tarmac roads as well as rougher terrains. Their strong traction enables them to handle sandy or marshy roads, the bold tread pattern prevents mud and water from clogging and they also provide a quite comfortable ride quality, even on rocky terrain.
Run-flat tyres: A newer addition to the tyre market, run flat tyres can keep going even if they are punctured and lose air pressure. That said, you will still need to get the damaged tyre changed once you reach home or get to a garage; you’ll simply be able to avoid having to pull over in the event of a puncture or loss of pressure.
Eco tyres: With more and more motorists becoming environmentally conscious, eco tyres allow for a reduction in fuel consumption without compromising on performance. Silica is added to the tyre’s tread compound, which decreases the resistance of tyres during ‘rolling’ without a corresponding loss of grip, and it also lowers fuel consumption. Eco tyres can potentially save motorists more than £50 a year.
4x4 tyres: These are designed specifically for vehicles with four-wheel drive. 4x4 performance tyres provide motorists with excellent grip on all road surfaces and have all the quality of high-performance tyres, except with a far greater lifespan due to their hard tread compound.
Asymmetric tyres: These have differing tread patterns between their inner and outer edges, with the small inner tread blocks improving grip on wet roads and the large outer tread blocks helping with cornering. The middle of the tread is stable and consistent, and these tyres provide an excellent overall performance.
Directional tyres: These are designed to rotate in one set direction as indicated by an arrow on the tyre’s sidewall. They are ideal for dispersing water, reducing road noise and improving directional stability.
Temporary tyres: Widely known as spare tyres, these are contained within the boot/trunk of your car and are smaller and lighter than normal tyres. They are intended solely as an emergency backup measure and should be returned to the boot/trunk as soon as you can get the original tyre replaced adequately.
How long do tyres last?
In truth, there is no hard or fast answer as to how long a tyre should last. The reality is that the lifespan of your car’s tyres can vary depending on several factors, as outlined below:
Tyre type: As outlined in the previous section, certain types of tyres are designed to provide high quality in certain conditions, although this can be offset by the tyre having a shorter lifespan than normal.
Driving style: Sharp cornering and sudden braking will cause your tyres to wear very quickly.
Position: Tyres at the front of your car will wear quicker due to the level of strain put upon them while driving. It is strongly recommended to rotate your tyres frequently so as to ensure an equal lifespan for the full set of tyres on your vehicle.
Speed: Regular driving at high speed will wear down your tyres very quickly.
Weight load: The more weight that is in the vehicle from passengers and luggage, the more of a strain is put on your car’s tyres, causing them to wear more quickly than usual.
Tyre pressure: Tyres should be inflated to a specified pressure. Going too far under or over this specification will lead to the tyres wearing very quickly.
Alignment: Your wheels should be aligned correctly so as to avoid uneven and premature tyre wear.
How to calculate your tyres’ size
If you look closely at your tyres, you may see a set of numbers like 200/50/16, to give an example. Each of these numbers corresponds to the size of the tyre. Taking the example above, let’s examine what each of these numbers means.
The first figure (200) refers to the width of the tyre in millimetres.
The second figure (50) refers to the percentage ratio of the tyre’s width to its height. In this case, the tyre has a height of 100 mm (200 x 0.5).
The third figure (16) refers to the inside diameter of the tyre in inches.
To calculate the standing height of your tyre, convert its aspect height (100 mm) into inches by dividing by 25.4. In this example, the tyre is 3.94 inches high. As you need to account for both the top and bottom sidewall, multiply the height by two (7.88 inches in this example) and add the inside diameter. We have now determined the standing height of the tyre, in this case 23.88 inches (7.88 + 16), and when purchasing new tyres, you now know the size of the tyre that will fit best for your car.
You can find an online tyre size calculator here.
Changing a tyre: instructions and advice
Changing a tyre is something that all of us will have to do at some point, so it is hugely important for drivers to know how to change a tyre.
1. Ensure that there is nobody inside the vehicle.
2. Pull up the handbrake and put the vehicle in park (if automatic) or in first gear (if manual).
3. Block the wheels on the side that you’re not lifting.
4. Remove the wheel cover and loosen (but don’t remove) the wheel nuts with a wrench while all of the vehicle’s wheels are still touching the road.
5. Place the jack in the correct jacking point on a firm, even surface and slowly raise the vehicle.
6. Remove the wheel nuts (you should be able to do this by hand provided they’re loose enough) and then use both hands to pull off the wheel.
7. Attach the spare tyre and replace all the wheel nuts, twisting them in by hand as far as possible.
8. Use the jack to lower the vehicle back onto the ground and tighten the wheel nuts with the wrench.
9. Replace the wheel cover and go straight to a tyre shop to get the damaged wheel replaced or repaired.
Practice changing a tyre while parked outside your home if you haven’t done so before. When doing so, make sure that there is somebody with you who can affix the tyre if you struggle with changing it.
Always keep a small plastic sheet or mat, a pair of gloves and a torch with spare batteries in your car, as you may have to change your tyre at any time.
Put on your vehicle’s hazard lights if changing a tyre at the side of the road.
Do not attempt to change a tyre without the correct tools. If you don’t have a jack or adequate tools to hand, call for assistance.
If there is another person with you when changing a tyre, either get them to guide you as you change the tyre, or vice versa. If changing a very heavy tyre, ask them to help you with moving it.
How to check for the correct tyre pressure: instructions and advice
1. Find out the correct pressure for your tyres by checking either the vehicle’s handbook or the inside of the driver’s door or fuel cap. You can also calculate the correct pressure for your tyres here.
2. Unscrew the plastic cap on the tyre’s air valve.
3. Press the tyre pressure gauge against the valve and keep it held firmly. If you hear a hissing noise, this means that air is escaping and you will need to press harder.
4. Read the measurement that the gauge is showing.
5. If you need to add more air, keep pumping the gauge until it shows the correct tyre pressure. If you need to deflate the tyre slightly, stop holding the valve firmly until such a point that it shows the correct tyre pressure.
6. Once the correct amount of pressure has been reached, screw the plastic cap back onto the valve.
Check the pressure of your tyres at least once a month.
Only check for tyre pressure when the tyres are cold, so as to get a true reading.
Always check the pressure of your tyres before undertaking long journeys.
Underinflated tyres can go flat and build up internal heat, as well as reducing fuel economy.
Overinflated tyres have very little grip on the road and can easily be damaged if they encounter debris or potholes.
How to check tyre tread
The legal tyre tread depth under UK law is 1.6mm. If your tread is any lower than this, your tyres are very unsafe and immediately need to be replaced.
You can easily pick up tyre tread depth gauges to measure the depth of your tyres’ tread. To check the tyre tread, slot the gauge into one of the grooves on your tyre and take a reading from the gauge.
A brand new tyre will usually had a tread depth of approximately 8mm. This will wear down throughout the lifespan of the tyre and when the tread reaches 3mm, it is recommended that you change your tyres, as the performance of tyres begins to reduce substantially once the tread is less than this. It is illegal to drive on tyres with a tread depth of less than 1.6mm.
You should check your tyre tread at least once a month, as well as before and after long journeys. There are also some warning signs to look out for which, if apparent, may have a critical effect on your tyre tread. These include:
Being able to see the tread wear bars on the tyre’s sidewall.
An item (e.g. a nail or thumbtack) being lodged in the tread.
The tyres appearing worn on their edges or in the centre.
Uneven wear across one or all of your tyres.
A saw-toothed/feathered appearance around the edge of the tyre.
Tyre rotation guide – what is the proper way to rotate tyres?
This diagram shows the proper way to rotate tyres for both front wheel drive and rear wheel drive vehicles.
Tyres wear out at different rates, depending on where they are positioned. Tyres at the front of your car will wear considerably quicker than those at the back, as there is greater pressure being applied to front tyres, so it is well worth rotating your tyres every few months in order to get the most out of them. That said, rotating your tyres won’t correct any problems associated with overinflated or underinflated tyres.
Generally speaking, you should rotate your tyres every 10,000 km (6,250 miles) so as to maximise the life of your tyres. However, depending on your driving circumstances, rotation may be needed even sooner. For example, if you drive for a living and you routinely carry heavy loads or travel long distances, your tyres are going to wear at a faster rate than normal. Also, if you notice warning signs such as uneven tyre wear or a humming noise on a smooth road, rotation is advisable.
While many motorists attempt to rotate their own tyres, it is a job that is best left in the hands of a professional mechanic, who has instant access to all of the best tools for the job and who can carry out an expert service while also dispensing some essential advice. Let them do the dirty work; your leisure time is for enjoyment!
Tyre maintenance tips
In the event of scratched or damaged tyres/wheels, it is often a good idea to get them refurbished.
Don’t spin your tyres excessively if your vehicle is stuck in tricky conditions such as snow, ice or mud. This could cause tyres to overheat and become irreparably damaged. A gentle back and forth rocking motion is a far better way to get your vehicle out of such difficult terrain.
When carrying out your monthly pressure check, inspect all of your tyres fully for signs of damage such as cracks, bulges and buckling. If you notice any such warning signs, take your car to a garage without delay.
Never attempt to mount your own tyres.
Never mix tyre sizes and types. For best results, all of your tyres should be from the same manufacturer.
Always consult the vehicle owner’s manual when changing tyres to ensure that you are abiding by the car maker’s specifications.
Do not overload your vehicle or use tyres with an insufficient load-carrying capacity.
If using specialist tyres such as winter tyres, ensure that all of the wheels are fitted with the same type of tyre, i.e. don’t just put winter tyres on the two front wheels.
Your tyre selection should be consistent for all of the wheels, i.e. same type, speed rating, etc. It is OK to use a mixture of radials and non-radials, but not on the same axle.