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So, what are tyres?
Tyres are essentially rubber shoes for your car filled with air or nitrogen with the primary material used to make tyres being rubber. They act as a good buffer that absorbs many of the small shocks from the road.
Construction of Car Tyres
Tyres may seem like simple rubber circles but there is so much detail that goes into the making of a tyre. It’s a complex engineering process that has a lot of physics and chemistry in it. Multiple layers made of multiple compounds working together.
Design
Different tyres can perform very differently because there is a wide variation in the design of tyres. We need different tyres for various functions eg: variations in the design of passenger tyres, heavy-duty off-road tyres and others. Depending on load and operating conditions, the components included in the tyre may vary. Compared to passenger tyres, heavier tyres like truck tyres may have additional ply layers, belt, breakers, or a heavier sidewall.
Often, tyres are designed to meet unique requirements specified by car manufacturers and for each vehicle model. As each car runs differently, it makes sense that in order to optimise performance it needs to be paired with the right tyres.
Materials and Components
It’s not just rubber, an average tyre has. It has numerous compounds in the final product. The base material used in the tyre is natural as well as synthetic rubber. Additionally, carbon black, silica, oils, sulphur, antioxidants, and so on are used as fillers. This is done right at the mixing stage to produce the sheets. As for other components, steel wire is covered in a rubber compound to form the bead. It is joined with the apex. Moreover, angled steel wires are used as breakers.
Assembly
Firstly, the carcass of the tyre is assembled. The bead and apex are joined with inner liner and body ply layers, and finally with the sidewall. The sidewall edges are then turned down mechanically to complete the basic carcass. On a different assembly, we would have a belt drum. Here the belt is brought together, layering the ply with breakers, and then laying the tread. The belt assembly is then brought to the carcass and they are joined together. Compressed air is used for joining to ensure cohesion.
The final manufacturing step is cooking, or vulcanization if you prefer to be more civilised. The “green tyre” is placed in a patterned mould. The pattern is pressed into the tyre during the process. Rubber curing bladders are placed inside the tyre with high-pressure steam inside, that expands when the mould is closed. The process is done in high temperatures. For passenger tyres, it takes about 10-15 minutes.
The tyres are removed after the required time. Like a baked bun out of the oven, they are then cooked and ready.
Before they hit the road, the tyres also need to go through rounds of quality inspection. Dimensional accuracy, surface uniformity, and so on, are checked and confirmed. It may be limited to visual and basic x-ray examination. Or it can include detailed lab tests and road tests.
Parts of the tyre
Casing
The tyre casing is comprised of everything except for the steel belts and the treads. But the plies, beads, inner liner and even the sidewall are a part of the casing.
Sidewall
The sidewall is the surface that makes up the sides. It is the portion on either plane, from the rim bead to the tread. The sidewall displays tyre markings referencing its size, load index and speed rating.
Tread
This is the part of the tyre that comes in contact with the surface of the road. The tread has grooves and sipes that renders the required traction on the ground. However, the tread wears over time.
Tread Patterns
The tread patterns are also called grooves. We see these grooves in the tread of the tyre. The tyre can grip the road well, thanks to these grooves. Moreover, on wet roads, these grooves limit aquaplaning. The tread blocks also bear smaller channels or sipes that check skidding on icy roads.
Ply
The casing of the tyre has many layers that are composed of strings made of rubber-coated fabric. The fabric most commonly used here is polyester but we can find nylon or rayon in the plies as well. Plies in the tyre keeps the tyre in the required shape. They also make them stronger and more resistant to tread wear.
Belt
The tyre has belts that are essentially wires made up of steel. The rubber-coated steel wires are made into overlays that are placed around the tread of the tyre. The belts thus bolster the strength of the tyre.
Beads
Beads are the edge of the tyre that touches the rim. The rim on the other hand is the outer perimeter of the wheel. Consequently, the beads act as fasteners that make sure that the tyres stay fixed on the wheel. The beads too are made of rubber-coated steel.
Shoulder
It is the edge of the tire where the sidewall meets the tread. Shoulder of the tyre is the part between the sidewall and the tread. The shoulder might carry treads that might look distinctive from the rest of tyre, but not always. However, if the tyre loses pressure, the weight of the vehicle gets shifted to the edge of the tyre, that is to their shoulders. Shoulder wear can also be caused by over-inflation or bad suspension.
Which type of car tyre should you choose?
All-weather Tyres
Automobile tyres come in different shapes and sizes. You would have to decide which tyre would fit your requirements. Depending on what you use your car for and how you drive it the tyre you need would differ. Besides the weather conditions would also dictate the kind of tyre you should choose. Different vehicles would also demand different tyres. Your choice of tyres will also depend on whether you prefer a greater grip or stability on the road. If you want high-performance tyres, you can swap the ones you got from the manufacturer with these. Since tyres affect the performance of your car choose your tyres wisely.
Standard Tyres
They are made for normal weather conditions and provide greater traction on dry and wet roadways. These tyres have bigger tread blocks compared to other season tyres. Additionally, in rain, standard tyres have greater resistance toward hydroplaning. Hydroplaning happens when a layer of water gets trapped underneath the tyre. Standard tyres are also called summer tyres. They are named so because they are no good if the temperature drops below seven-degree Celsius. But, compared to winter tyres, the performance of the summer tyres is inferior.
Winter Tyres
When you are driving in snow or ice, winter tyres are safer to use than standard tyres. In most of South Africa, the weather is generally warm – at least in most parts of the country. Therefore, you can get away using standard tyres all throughout the year. But you would have to invest in winter tyres, if you are living in the few colder parts, where snow and ice are common in winter. Winter tyres use more silica compared to summer tyres. These tyres would give the vehicle a better footing on snow. Also, they have more tread pattern and sipes meaning a higher adhesion on wet pavements.
All-Terrain Tyres – Off-Roading –
A/T tyres installed on SUVs do well in all terrains.
SUVs and other utility vehicles with four-wheel drive are often fitted with all-terrain tyres. All-terrain (A/T) tyres are good in the tarmac laden roads of the city. They also do well off-road, no matter what terrain they are driven on. The elevated areas on the treads of the tyre are called lugs. A/T tyres have stouter lugs and hence they provide great friction.
Touring Tyres – Great for urban roads
These are premium tyres. Touring tyres are usually fitted on luxury cars. These tyres are great for the city road and often carry a speed rating of S or T. Besides they are not very noisy either. Many of these touring tyres also act as all-season tyres. It means you won’t have to switch out to winter tyres.
Performance tyres
They provide the greatest traction and road grip even when the vehicle is moving at top speeds. Performance tyres leave you feeling more settled even while making turns. They have plenty of tread patterns and are customarily outfitted on sports cars.
Radial Tyres
Tyres can also be classified as radial and diagonal based on how plies are laid one on top of the other. In radial tyres, plies are arranged to overlap each other, perpendicular to the direction of rotation of the tyre. Radial construction is most commonly found in tyres.
Diagonal Tyres
In diagonal tyres, plies are placed diagonally at a 55-degree angle to the central line of the tyre. The nylon cords are arranged diagonally in the tyre. They are also called bias tyres. Tyres with bias-ply are the best when the vehicle they are mounted on needs to carry a lot of heavy cargo.
Tyre Markings Explained
The sidewall is a repository of information about the tyre. When you need to buy new tyres for your car, do ensure that the car manufacturer’s requirements match with what the new tyre offers.
The tyre size sequence
The most important marking on the sidewall of the tyre is the tyre size code. Here in the picture, the sequence that tells you about the dimensions of the tyre is 185/55R16. In many tyres, there would be alphabets LT or P engraved on the tyre before the code. LT and P stand for Light Truck and Passenger respectively. Application of the tyre tells you which vehicle it can be mounted on.
185: The width of the sidewall
The width of the sidewall of the tyre is given in millimetres. The tyre in the picture has a sidewall that is 185mm wide.
55: The aspect ratio
In order to find the sidewall height from the tyre markings, we would have to look at the aspect ratio. We can understand that 111.75mm is the height of the sidewall which is 55% of the tyre width (185mm).
R: Construction of the tyre
Most tyres have radial construction. Tyres also come with the alphabets B or D to denote its construction. B and D stand for Bias or Diagonal respectively. Tyres that have bias plies have layers of rubber-coated sheets placed at an angle to the axis of rotation. Therefore, by studying the tyre markings we can also understand how the tyre is constructed.
16: The rim diameter
It is exactly what it sounds like. The rim diameter is the diameter of the wheel the tyre is placed on. The rim diameter is given in inches. This Bridgestone’s Ecopia tyre in the picture should be on the wheel that has a diameter of no less than 16 inches.
Load Index and Speed Rating
These are usually given after that tyre size sequence. Here in the picture 83H denotes the tyre’s load index and speed rating. 83 is the load index or the maximum weight-carrying ability of the tyre.
The maximum weight a vehicle can haul would be 4 times the weight an individual tyre can lug. When buying new tyres keep the load index in mind.
The speed rating is the maximum speed a tyre can handle. You should choose tyres that have a speed rating that is equal to or above the speed rating of your vehicle. Alphabets are used to denote the speed rating. Each alphabet corresponds to the maximum speed the tyre can handle. You can always check the car manual to know the kind of the tyre you would need to put in.
Similarly, here are some of the commonly seen alphabets that are used to speed rating. Each of the alphabets corresponds to a certain speed.
Speed Rating Maximum Speed (km/hr)
L 120
M 130
N 140
O 150
P 160
Q 170
R 180
S 190
T 200
U 210
V 240
W 270
Y 300
Additional Tyre Markings
Aside from the markings given above, your tyre can have other markings as well. Let us look at the others like the maximum load rating, maximum permissible inflation pressure, treadwear number and others.
Maximum Load Rating
Load rating says the same thing the load index tells you. That is it is the utmost weight the tyre can bear.
Maximum Inflation Pressure.
It is the maximum air pressure the tyre can withstand. But, you should not inflate the tyre to this point. This is because the ideal inflation pressure for your tyre will be lower. You will probably find it in the manual.
Treadwear Number
Higher the treadwear number the longer will it take for the tyres to wear out. However, the treadwear numbers would be brand specific. That is, we cannot expect the same performance from the tyres of two different brands with the same treadwear number.
Traction Grade
Tyres are rated as AA, A, B or C according to the traction they exert on wet ground. Traction grade denotes how much would the tyre keep travelling even after you hit the brakes in rain. Greater traction implies faster halting.
Temperature Grade
Tyres with higher temperature grades can endure the most heat. Tyres that have a temperature grade of A won’t be damaged even at a higher temperature.
The year of manufacture
The tyre markings can also tell you when it was made.
Tyre Damage
Your tyres will get damaged sooner than later. The tyre damage your vehicle can sustain can range from irregular wear to flats and bulges. First lets us look types of irregular tyre wear.
Centre Tyre Wear
If you inflate your tyre more than necessary, the centres of the tyres are going to take the brunt of the damage. This means the centres would have more wear than the sides. But the centre wears can also be caused due to other reasons as well. This can be attributed to the greater levels of torque produced during sudden acceleration. So this wear is a common sight in cars that have a relatively powerful engine.
Side Tyre Wear
It is under-inflation that causes tread wear to concentrate on the sides and not the centre. Poor alignment can also lead to side wear.
Feathering
Badly aligned wheels can cause feathering, where also the tyre becomes worn in an uneven manner. If you feel like the treads on the same tyre is worn smooth on one side but not so much on the other, this might be an indication of feathering. Making turns at higher speeds can also result in feathering. Tyre damage from feathering can be prevented by rotating the tyres.
Heel and Toe Wear
Heel and toe wear can be spotted in the direction of the rotation of the tyre. This kind of wasting away takes place as a result of normal driving. Treads are thus worn out in the form of a heel and toe pattern. Heel and toe wear can be fixed by rotating the tyres on a regular basis.
Other Tyre Damages
Your tyre can also sustain punctures, cuts, bulges, cracks and other damages.
Punctures and Cuts
Your tyre can get punctured by debris on the road. Any sharp objects like pieces of glass, stones or a nail on the pavement can potentially give you a flat tyre. Cuts and tears too can be caused by sharper debris biting into your tyres. If driving over pothole results in cuts deep enough to expose the cords you should take your car to a mechanic right away.
Breaks and bulges
This can be spotted on the casing of the tyre. Breaks can be the result of hitting a harsher object on the tarmac. Additionally, if too much pressure is placed on the carcass of the tyre, the cords can break. Broken cords can result in a bulged sidewall. PLEASE do not drive with a worn-out tyre
How to take care of your tyres
Tread of a Tyre
Either pop in to a Super Tyres branch to have them checked, or manually check your tread depth. Treadwear is a serious issue that should be addressed immediately. To take care of your tyres, make sure you drive slowly on bad roads and don’t forget to drive slowly and carefully over speed bumps, potholes and debris on the road.
Monitor the air pressure of the tyre from time to time. You can check your car manual to figure out the right inflation pressure for your tyre. This is because if your tyre has low air pressure, more surface area of the tyre would come in contact with the road. As a result, the tyre could wear more quickly.
Underinflation can also increase the chance of a blowout. On the other hand, overinflation exerts a lot of stress in the centre of the tyre. The centre of the tyre would swell and can wear out untimely. This means too much air pressure can cause the tyre to blowout as well.
Tyre Rotation
Tyre rotation is very important and ensures an even wear on all the tyres. You can rotate your tyres after every 8000km or so. But how are the tyres rotated? Each tyre is taken off of its position and is put on the rim of another wheel. If your car has a rear-wheel drive, you can remove the front-right tyre and place it on the rear-left wheel. By using the cross pattern you can rotate the other two as well. If you rotate your tyres you can save a couple of trips to store to get new ones.
Wheel Balancing
Another way to make the tyres wear evenly is by balancing. Balancing makes sure that the weight allowance around the car is even. If you feel some irregular vibrations you should go to the service centre to get your tyres balanced. Tyre balancing is done using a balancing machine. Any imbalance is fixed by adding weights. The tyres would then travel smoothly and evenly once you balance them.
Wheel Alignment
You don’t have to align your wheels as frequently as you rotate or balance them. Wheel alignment is fixing the angle of the wheel so that the car can run straight. This is when we tweak the car’s suspension for correcting the angle the tyre makes with the road. Bring your car to your trusted Super Tyres branch if…
