Read Your Tyre Size
Understanding your tyre size will make the selection of your next tyres a lot quicker and easier. Tyre size contains information pertaining to its manufacturer, size, model etc. You can find this information on the sidewall of your tyre and it will read something like: 195/55 R16 87V. The following is an explanation of all terminology used for both regular and low profile tyres:
For a tyre size of 195/55 R 16 87V
Nominal Section Width:
The first three digit numeric portion identifies the tyre's "Section Width" (cross section) in millimeters.
Here the 195 indicates that this tyre is 195 mm across from the widest point of its outer sidewall to the widest point of its inner sidewall when mounted and measured on a specific width wheel.
The two digit number followed by the Nominal Section Width is a two digit number that identifies the tyre's profile or aspect ratio. The number 55 in the above diagram indicates that the tyre's sidewall height is 55% of its section width. The higher this number, taller the sidewall of the tyre, lower this number, lower the sidewall.
A letter (R in this case) that identifies the tyre's internal construction follows the aspect ratio. The tyre size above identifies that the tyre has a Radial construction in which the tyre body plies out from the imaginary center of the wheel.
The number 16 followed by the construction in the above diagram indicates the tyre and wheel diameter in inches. For information about the Load and Speed Index refer to the next section.
Speed symbol on your Tyre
It is very important that you check your speed symbols before buying your tyres. Even, when you are replacing your vehicle's tyres it is important to ensure the new tyres, even, if they are of a different size, have the same or a higher speed symbol. Speed symbol determines the maximum speed at which it can carry its rated load. For the illustrated tyre in the above section, the symbol V limits its maximum speed to 240 kmph. Likewise, there are other speed symbols, whose related speeds can be viewed in the table below.
Load Index on your Tyre
The number following the rim diameter indicates the maximum load that the tyre can carry. Usually a rough load estimate of a tyre is determined by dividing the total load capacity of the vehicle by four and checking the result (Total Load Carrying Capacity) for the associated load index in the table below. Some vehicles require tyres that are rated to carry a higher load and therefore have a higher inflation pressure. This information is contained in the manufacturer's handbook and the tyres will carry the marking RF (Reinforced) or XL (Extra Load).
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Tyre Types On The Basis of Construction
There are two distinct types of construction for tyres - Bias ply and Radial ply. The construction method affects the durability, ride and fuel economy of the tyres. In India Radial tyres are the most common on cars and trucks are still largely on Bias Tyres.
Bias Type Construction
Tyres have belts called plies that give a tyre its shape. Plies may be the layers of Polyester, Fiberglass or Steel Cords embedded in the rubber of a tyre. A Bias-ply tyre has the layered belts running at angles to each other and to the body of the tyre.
Radial Type Construction
Radial-ply tyres have the belts at a 90-degree angle to the tyre, and the belts overlap rather than cross each other. Radial tyres have another belt, usually of steel cord, running around the tyre under the tread.
Radial construction allows the sidewall of the tyre to flex under loads without affecting the contact of the tread with the road.
Advantages of Radial Tyres
Michelin introduced and patented the radial tyre in 1946. Since then, radial type construction has been recognized in the world for its advantages over the bias tyres. There are still applications where bias tyres are suitable, but radials offer benefits that bias tyres cannot. These benefits make radials a preferred choice for the most.
The advantages of a radial tyre are due, in part; to the way the tyre is constructed. Coated steel cables run from bead to bead perpendicular to the circumferential center line of the tyre. Steel belts are then laid over the radial plies under the tread of the tyre. This forms a two-part construction in which the sidewalls are a separate unit from the tread structure.
The strength of the multi-layers of steel belts makes the tread resistant to punctures. The two-part type construction of the tyre structure allows the sidewalls to flex independently from the tread. This allows the tread to stay in contact with the road surface even while the sidewalls flex under a load or while cornering. This greatly reduces the chance of foreign objects puncturing the sidewalls since the sidewall doesn't "roll over" to present itself to the road surface.
The same construction elements that make the radial tyre puncture resistant also give it better traction than bias ply tyres. The radial's tread stays in contact with the road surface even under a load. A bias ply tyre will distort its tread under a load and so it reduces the amount of tread area that is in contact with the road surface.
The steel cables in radial tyres act as a heat sink to neutral the affect of heat. This keeps the tyre running at a cooler temperature than an equivalent-sized bias tyre. The plies of a bias tyre hold heat and so are more prone to blowouts when the tyre heats up during sustained highway driving.
The radial tyre-due to its two-part construction-offers a quieter, smoother ride than the bias tyre. It is also more fuel efficient since it offers less resistance to the road surface. This is a term referred to as "rolling resistance." Overall, radial tyres have longer life compared with bias tyres under similar workloads and environments.
On the Basis of Purpose
There are several different types of tyre that you can buy for your car. What you choose depends on how you use your car for, where you live, how you like the ride of your car and a variety of other factors. The different classifications are as follows, and some representative examples are shown in the image on the left.
Performance Tyres or Summer Tyres
Performance tyres are designed for faster cars or for people who prefer to drive harder than the average consumer. They typically put performance and grip ahead of longevity by using a softer rubber compound. Tread block design is normally biased towards outright grip rather than the ability to pump water out of the way on a wet road. The extreme example of performance tyres are "slicks" used in motor racing, so-called because they have no tread at all.
All-round or All-season Tyres
These tyres are what you'll typically find on every production car that comes out of a factory. They're designed to be a compromise between Grip, Performance, Longevity, and Noise and Wet-weather Safety. For increased tyre life, they are made with a harder rubber compound, which sacrifices outright grip and cornering performance. For the majority of the world's drivers, this isn't an issue. The tread block design is normally a compromise between quiet running and water dispersion - the tyre should not be too noisy in normal use but should work fairly well in downpours and on wet roads.
Rather than using an even harder rubber compound than all-season tyres, wet weather tyres actually use a softer compound than performance tyres. The rubber needs to heat up quicker in cold or wet conditions and needs to have as much mechanical grip as possible. They'll normally also has a lot more sipping to try to disperse water from the contact patch.
Snow Mud or Ice: Special Winter Tyres
Winter tyres come at the other end of the spectrum to performance tyres, obviously. They're designed to work well in wintery conditions with snow and ice on the roads. Winter tyres typically have larger and thus nosier tread block patterns. In extreme climates, true snow tyres have tiny metal studs fabricated into the tread for biting into the snow and ice. The downside of this is that they are incredibly noisy on dry roads and wear out both the tyre and the road surface extremely quickly if driven in the dry. Mud snow tyres typically either have 'M S' stamped on the tyre sidewall. Snow Ice tyres have a snowflake symbol.
All-terrain tyres are typically used on SUVs and light trucks. They are larger tyres with stiffer sidewalls and bigger tread block patterns. The larger tread block means the tyres are very noisy on normal roads but grip loose sand and dirt very well when you take the car or truck off-road. As well as the noise, the larger tread block pattern means less tyre surface in contact with the road. The rubber compound used in these tyres is normally middle-of-the-road - neither soft nor hard.
At the extreme end of the all-terrain tyre classification are mud tyres. These have massive, super-chunky tread blocks and really shouldn't ever be driven anywhere other than loose mud and dirt. The tread sometimes doesn't even come in blocks any more but looks more like paddles built in to the tyre carcass.
Tyre type on the Basis of Tread Pattern
Symmetric tread design can be commonly seen on the tyres of many cars. As their name itself indicates, symmetrical pattern refers to those treads which feature similar continuous design across the tread on either sides of tyre.
Tyres with this type of pattern are normally non-directional, meaning that they can be fitted without worrying about a specific rotational direction.
Exactly opposite to the symmetric tread pattern - asymmetric tyre treads feature dissimilar designs on both the sides. This discrepancy in their design allows better grip on flat out roads and also while making turns.
Generally, the outer area of such tyres has broad design where as the inner carries smaller independent tread blocks, as seen on symmetric design.
The unidirectional (also known as directional) tread patterns are made to perform well when fitted on a specified direction, this direction is generally marked with help of an arrow on the sidewalls.
This type of tyres have 'V' shaped tread design which helps increasing aquaplaning resistance when the vehicle is running on high speeds, by efficiently cutting it through this unique pattern.
Tyres are essential components for your safety. The only point of contact with the ground, it must allow for acceleration, cornering and braking whatever the road, driving or weather conditions. All while giving drivers and their passengers a feeling of comfort.
Tubeless Tyres are tyres without the tube. The tyre is built in such a way that it can contain the air by itself. It does not require a tube within it. The tyre and rim assembly form an air container, to "Seal" and "Contain" the compressed air inside the assembly. The tyre has a chloro-butyl lining on its inside which is airtight. Together with the airtight joint between the tyre and the wheel, the membrane forms a container that holds the air. A valve is fitted on to the rim for inflation or deflation to the assembly.
These tyres are more economical. As the tube is eliminated, friction between tyre tube is not experienced, thus lowering rolling resistance, improving fuel efficiency, producing fewer vibrations and heat and better comfort. Chances of tube pinching under the bead while mounting are eliminated. The number of components used in a tyre wheel assembly gets reduced. The tube and the flap are both eliminated. Lower tyre/wheel weight (un-sprung mass) results in better vehicle handling and therefore longer life.
In case a nail or other sharp object penetrate a tubeless tyre, the air loss is not sudden. The tyre wheel assembly continues to perform its function for some time before going flat. This is one of the biggest advantages of a tubeless tyre. If there is a sharp penetration in a tube tyre, the air in the tube starts leaking suddenly and rapidly in all directions. This causes the wheel assembly to loose stability thereby resulting in accidents. Since there is no tube in tubeless tyre, the probable and associated potential problems such as "Defective Splice", "Defective Valve Base", "Thin Gauge", "Foreign matter" or "Pin Hole" are eliminated, ensuring safety of the wheel assembly. Tubeless tyre beads are designed to seat on the rim bead seat area with higher "interference" (tight fit) as compared to a tube type tyre. In the event of air loss the chances of bead unseating from the rim is less, therefore providing higher safety.
The care and maintenance of your tyres is essential for your safety and that of your passengers. It also makes for a more comfortable driving experience. There are a number of simple steps that you can do that will not only improve the life of your tyres but also the performance and safety of your car.
Tyre Pressure and Spare Tyre
The easiest step to take in caring for your tyres is checking that all your tyres have the correct tyre pressure, including the spare. Under-inflated tyres cause poor steering and braking performance, leading to irregular tyre wear that will quickly reduce the life of your tyres. Excessive wear due to under-inflation can make your tyres prone to blowout. Over-inflation reduces the amount of tyre that is in contact with the road, reducing the braking ability and performance of your car. Regularly check that your tyres have the correct pressure in accordance with your vehicle's recommendations. You can find the correct pressure noted in your vehicle's handbook or on a plate or sticker on your vehicle, often on the inside of the driver's door.
Unbalanced wheels will cause the steering wheel to wobble at higher speeds. Improperly balanced wheels can also cause problems in other areas of your car such as the suspension and braking performance. Incorrect wheel balance is corrected by small weights attached to the rim of the wheel. As your tyres wear they naturally become unbalanced as the weight distribution within the tyre changes. Hitting a pot-hole or a kerb can also cause your tyres to lose balance. Get your tyres checked and balanced every 6 to 12 months.
A wheel alignment involves adjusting the suspension of the car and not the tyres. Poor wheel alignment can cause wear on different parts of your tyres, depending on how the tyres are misaligned. Incorrect wheel alignment can also cause steering problems and the necessity to continually compensate steering whilst driving. Your wheels should be checked for alignment every 6 to 12 months.
As front and back tyres will also often wear at different rates and positions, regular tyre rotation will extend the life of the tyres. Tyres should be rotated as part of your regular service.
Tightness of Wheel Nuts
Check on a regular basis that your wheel nuts are tight and not loose. Incorrect tension can cause problems with wheel balancing.
It is important to have the same type of tyres on your car. Tyres have different patterns, density and wear characteristics. Having different models and makes of tyres on your car can cause problems with wheel alignment and difficulties with automatic traction control.
Check for Nails
A common reason for tyre replacement is nails puncturing the tyre. Whilst nails often do not cause immediate deflation, a slow leak will cause irregular wear and the need for the tyre to be replaced. Nails when detected early can be easily repaired by a qualified tyre fitter.
Check for Tread Depths
Tread pattern designed on the tyre surface are designed to keep water out and maintain a contact between tyre and road where the rubber maintains a good amount of grip and maintains it. When the tyre wears out the grooves also wears out thus increasing the aquaplaning and loss of control. So once the groove depth decreases below 1.6mm one should try to look for replacements. Tread depth should be at least 1.6 mm across 75% of tread depth.
Looking after your tyres can prolong their life and ensure the safety of your vehicle. It is good to know what to look for when assessing the condition of your tyres.
Wheel alignment sometimes referred to as tracking, is part of standard automobile maintenance that consists of adjusting the angles of the wheels so that they are set to the car maker's specification. The purpose of these adjustments is to reduce tyre wear, and to ensure that vehicle travel is straight and true (without "pulling" to one side).
Alignment is one of the key maintenance factors in getting the most wear and performance from your tyres. In addition, wheel alignment provides safe, predictable vehicle control as well as a smooth and comfortable ride, free of pulling or vibration, and improved gas mileage. Wheel alignment is done for proper return ability, less tyre wear, reduce load on suspension and better handling. Improper wheel alignment can effect driving performance of your vehicles as well as cost you money. It also improves your vehicle's gas mileage by decreasing your tyre's resistance and improves safety by avoiding steering accidents.
There are three main parameters of Alignment, Camber, Caster and Toe. Return ability is the ability of the steering to get into position while the wheel moves.
Camber is the inclination of the tyres when viewed from front. The camber is negative if the top of the wheel leans inwards and if it is leaning outwards then the camber is positive. Positively cambered tyres are beneficial during rains to drain the water. To stay in a straight line positive camber is set on the front tyres. Rear tyres have zero camber.
The inclination of the steering pivot to the front or backward direction, to adjust the steering is Caster. The front angle indicates positive caster while the backwards indicate negative caster.
Rear wheel drive cars have positive caster and front wheel drive cars have negative caster. Caster is only made present in front wheels because of their ability to steer.
The difference of the lateral distance between the front end of the front tyres and the rear end of the front tyres is toe measurement. Toe-in suggests front end of the tyre is closer and in toe-out means it's away.
Tyre Rotation is an essential for longer tyre life and even its wear. With the front tyres having positive camber angle, the inside edge of the tyre wears faster, hence changing a front tyre with the diagonally opposite rear tyre will increase the life of a tyre, the tyre which is now at the rear end will wear from the centre as the rear end has no camber. The tyres should be rotated every 5,000 km even if there is no mention of the same in the manual.
Tyre pressure is a very important aspect in the wear of a tyre. The tyre pressure less than the recommended results in the wastage of energy. Also, if the centre of the contact patch doesn't touch the ground reducing the contact patch and tyre wear increases. When the tyre is overinflated, the contact patch is less, the efficiency increases a bit but the handling wears.
For the tyres to rotate smoothly and to prevent vibrations, the entire assembly of tyres has to be well balanced. If a wheel is not balanced, then one segment of the tyre will become lighter and the opposite end will become heavier causing the vibrations.
In static balancing, the wheel and tyre assembly is mounted on a hub and is rotated by hand. The tyre rotates and eventually slows down. While slowing down, the tyre begins to oscillate with reducing amplitude. Once the tyre comes to a halt, the lowest point is marked with a chalk and then again rotated after moving the mark end to 90 degrees from the lowest point. If the marked point again comes to a halt at the lowest point then this indicates that it's the heaviest point on the assembly and weight is added to the opposite side. This is continued till the wheel is balanced.
In this form of balancing, the wheel assembly is attached to the machine, which spins the whole assembly and calculates the amount of weight required at different locations to balance the wheel and tyre.
The tyre presently in use should be replaced with a new tyre when the tread wear indicator is exposed. The tyre wear indicator normally is present at a height of 1.6 mm.
Maintenance of Inflation Pressure
The inflation pressure recommended by the vehicle manufacturer should always be maintained. Inflation pressure of a cold tyre should always be maintained. Inflation pressure should be checked every week and before long drives. Air leakage should be checked for. The valve core should be renewed timely and lost valve cap should be replaced. New tyres tend to expand during a certain initial period and increase its volume. This decreases the inner pressure, so frequent checking of pressure is recommended up to 3000 kms. The inflation pressure of the spare tyre 5 psi (3.0 kgf/cm2) should be maintained, higher than the recommended pressure and before using, bring inflation pressure to the recommended pressure.
Adventure Driving Care
Never Maintain Low Inflation Pressure:
Lower inflation pressure leads to tyre rupture due to generation of heat. Hence, the pressure should be maintained at 5 psi (0.3kgf/cm2). The tyres should be inflated over the normal pressure before high speed racing.
Never Use Damaged or Repaired Tyres:
Damaged or repaired tyres not to be used during high speed driving as it increase the risk of a tyre burst resulting in accidents.
Never Use Worn Out Tyres:
Worn out tyres should not be used as it increases the risk of accidents due to poor braking and skidding.
What are Tips and Advice for taking care of Tyres?
Tyre care is must for your car. Here is the expert opinion that can be useful to you. In this section, we have pulled in a few important tips that would help you take precautions and avoid stranded situations.
Maintain Adequate Air Pressure:
Maintaining the tyre pressure recommended by the manufacturer elongates your tyre life. Under inflation of your tyre could leave the tyre under performed. Low pressure can also cause dislodging and creates a rolling resistance. This in turn increases the fuel consumption of the vehicle and premature tyre failure due to excessive wear on both the inner and the outer side. On the other hand Over-inflation can cause problems like unpredictable handling and accelerated centre tread wear.
Always Check Tyres When Cold:
As you drive, the friction heats up the tyre and increases the tyre pressure. Checking a warm tyre for pressure gives an underinflated pressure reading leading to wrong adjustment of tyre pressure. Therefore, tyre makers always recommend checking tyre pressure only when it is cold.
Avoid Mixing Tyres:
Car makers design cars to work with four tyres of same or similar make to ensure consistent performance. Different make and models of tyres perform differently, so applying different models of tyres will make your car suffer in terms of performance. Therefore, try and replace two tyres at a time and install two similar tyres on the same axle.
Check for Tread Depths:
Tread pattern designed on the tyre surface are designed to keep water out and maintain a contact between tyre and road to maintain a good amount of grip. When the tyre wears out, the grooves also wear out thus increasing the aquaplaning and loss of control. So once the groove depth decreases below 1.6 mm one should try to look for replacements. Tread depth should be at least 1.6 mm across 75% of tread depth.
Make sure that you keep a spare tyre with you for the emergency purpose with a proper tyre changing kit handy.
Frequent Checks for Damage Detection:
Visual inspection of tyres should be done frequently. Just because we do not feel that there isn't any problem with the tyre it does not mean that tyre is in a good condition. A tyre can be damaged by a nail or any other harmless object. Therefore, frequent checks on the tyres should be done and replacements should be timely made as the ageing tyres lose their resistance and develop cracks.
Look for wheels Steering and Suspension:
Misaligned steering or worn suspension can cause uneven or accelerated tyre wear. Checking the tyres frequently can avoid this. If these concerns arise check at a garage for wheel alignment and suspension condition and get it adjusted or repaired as required.
Know your Tyres before you Buy them:
Know all the tyre specifications before you buy them.
when to change tyre
If Your Tyre is Worn:
The safe limit of the tyre surface is 1.6 mm. Tyre treads worn out below this limit would prove to be dangerous. Use of worn-out tyres increase the probability of tyre failure, and in wet conditions can cause the tyre to lose traction suddenly. In most countries, it is illegal to drive with less than 1.6 mm of remaining tread depth.
If Your Tyre is Damaged
Your tyre can be seriously damaged if it impacts any solid object on the road e.g. kerb, pot hole a nail. There is a good chance that your tyre can be repaired, but only an authorized tyre retailer or technician can tell you whether the tyre can be repaired or has to be changed.
Inspection by a professional is absolutely necessary because internal damage is not visible while the tyre is mounted.
But in one of the following situation the tyre definitely cannot be repaired:
The usable life of tyres varies enormously and is impossible to predict. For this reason, it is recommended that all drivers pay attention to the external appearance of their tyres, to any loss of inflation pressure or any abnormal occurrence (Vibration, Noise, Lateral Pull) which might demonstrate the need to replace them.
Moreover, in addition to regular inspections and tyre pressure adjustment, it is also recommended that all tyres (including those on spare wheels, trailers, caravans and camping cars), are inspected regularly by a tyre specialist, who can assess whether they should continue in service. After five years or more of use, this inspection must be carried out at least once a year. Where necessary, follow the manufacturer's recommendations on replacement of original parts.
An easy test to know whether to change your tyre or not?