Car Tyres: Everything You Need to Know
Tyres are the only component on your car that actually make contact with the road surface. This makes them very important for safety while driving. The following comprehensive guide covers all you need to know about car tyres. It includes everything from reading and setting the tyre pressure to what size tyres you need is outlined. Following the advice given here will save you money, reduce hassles and most importantly keep you and others safe on the road.
What is my tyre's speed rating?
A tyre speed rating is the maximum speed a particular tyre should be legally driven at. You will find the rating on the tyre sidewall and is the last letter in the sequence. If the pavement reads 205/55 R16 W 91, for example, the speed rating is W. Each letter has a higher maximum speed. Therefore, in the case of tyres with a W speed rating, the tyre is approved for speeds up to 168mph.
For safety reasons, it does not exceed the speed rating of your car's top speed. Below is a complete list:
N - 87mph
P - 93mph
Q - 4 m
R - 106mph
S - 112mph
T - 118 m
U - 124mph
H - 130mph
V - 149mph
Z - 150mph +
W - 168mph
Y - 186mph
What is the legal tyre depth limit in the UK?
The minimum running depth required by law in the UK is 1.6 mm. This applies to the width of the tyre and the central three-quarters of its entire circumference. However, many car manufacturers recommend changing their tyres at 3mm down to tread to be on the safe side.
The penalty for driving a car on the road with a tyre having less than 1.6 mm is £ 2500 and three points on your license. So, if all four tyres are below that legal limit, you will face a £ 10,000 fine and 12 penalty points. This would result in a six-month driving ban.
What should my tyre pressure be?
You'll find the correct tyre pressure for your car on a sticker attached to the door frame, inside the fuel filler flap or in the handbook. Be aware that the car manufacturer may recommend different tyre pressures for the front than the rear. You'll also see different recommended pressures for different load levels. For example, having only two occupants or a full-fledged family of items in the other. Therefore, you must make sure you select the correct pressures for the load you are carrying.
It is very important that you set your tyre pressure correctly. If the pressure is too low, the car will feel unstable and may be unsafe to drive. It also results in tyres wearing out quickly and will affect your fuel economy. If you set them set too high, the tyres will not hold as much as they should and they will be heavier on the middle band of the tread.
How do you read the signs on a tyre?
The marks on a tyre indicate its size, load index and speed rating. A typical tyre marking looks like this - 205/55 R 16 W 91.
The first three digits - 205 - refer to the width of the tyre in millimetres.
The second two digits - 55 - refer to the aspect ratio of the tyre. This is the height of the sidewall and is expressed as a percentage of the width of the tyre. Therefore, an aspect ratio of 55 means that the pavement is 55% longer because the tyre is wider.
R stands for Radial. It means the tyre is built in the direction of travel with its cord plies positioned at 90dg. This adds strength. Almost all new tyres are radial.
The two-digit number, which in this case is 16, specifically indicates the diameter of the tyre wheel.
The final letter is the speed rating, as mentioned earlier. It is the maximum speed a particular tyre should be legally driven at. A rating of W indicates a maximum speed of 168mph.
Finally, the last two-digit number is the load rating. In this case, a load rating of 91 means that a tyre is legally approved to carry a weight of 615kg.
How do you check tyre running depth?
An easy way to check that your tyres have sufficient tread depth (the legal minimum in the UK is 1.6mm) is to take a 20 pence piece and move it to the running point at the point where the tray is in its shallowest position.
If you can't see the outer rim of the coin, your tyres have a lot of tide left and are safe. If you can see the rim, your tyres have probably reached the 1.6mm limit. It means it is time for new tyres.
How often should I replace my tyre valve?
The valve is a part of the wheel instead of the tyre. Made from rubber, it can corrode over time and leak air at a significant rate or at least make it difficult to check your tyre pressure. Ideally, you should change the valve every time you change your tyre.
The cost of replacing the tyre valve is minimal. In fact, you will often find that this cost is included in the price of a new tyre.
How do I check my tyre pressure?
First, you should check your car's handbook, the sticker you'll find on the door frame or inside the fuel filler flap or simply search online. This will allow you to find the correct tyre pressure for your car and its load level. Then you should remove the dust cap from the tyre valve and, using a tyre pressure gauge, read the current pressure. You should add air using an electric compressor if the pressure is too low and remove the air when it is too high. If you do not have a tyre pressure gauge or compressor, most petrol stations will have an airline.
Remember, tyre pressure will increase with heat and lower in cold. This means that you should check and adjust your tyre pressure to a representative ambient temperature (for example, if it is cold outside, do not set them in a hot garage) and when the tyres themselves are cool.
How long does a car tyre usually last?
There are too many variables to definitively answer this question. High-performance tyres will have a much shorter life than fuel-saving, low rolling resistance tyres. Also, determining your driving style, the type of car you drive and the way you drive are important factors.
As a general rule of thumb, a tyre of the appropriate quality suitable for the front axle of a front-wheel-drive car can run up to 20,000 miles.
How can I make my tyres last longer?
The key to prolonging the life of a tyre is to maintain pressure at the level recommended by the car manufacturer. Tyres tend to corrode very quickly due to very low pressure, while too much pressure will cause excessive wear of the central band due to tread. You should check your wheel alignment regularly by a garage because if the alignment is by the slightest amount, the tyres will wear out very quickly.
Driving carefully in corners and avoiding whip spins will also help reduce tyre wear. If you drive a front-wheel-drive car, you can switch the tyres from the front axle to the rear, and vice versa. This is best done when the front tyres are in the last third of their lives.
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