10/03/2014
Life of a car tyre
The life of a car tyre varies with the size and kind of vehicle. Small hatchbacks tyres have an average life of about 40,000 km, but some even touch 50,000 km. SUV tyres can go about 60,000 km. Some expensive sedans with low-profile tyres only manage about 30,000 km from their tyres. The life of the tyre also depends on the compound used – softer tyres have better grip, but last less. Harder tyres have longer life, but may not be good at grip.
But all these figures can vary drastically depending on the driving conditions and maintenance of the vehicle. If you drive on bad roads, or drive fast and brake hard, you can reduce tyre life by nearly 50%. Or if your car has an alignment or suspension problem, this too will badly affect your tyres. And then there’s tyre pressure – always maintain the recommended pressure, checking it every fortnight.
Tread pattern
There are various kinds of tyres for different driving applications. All tyres have speed limits and load limits, which you will find on the sidewall markings. The tread pattern also varies. Unidirectional tyres only have the tread pattern in a single direction and you can’t swap these tyres to the opposite side of the vehicle during wheel rotation. All-terrain tyres have a deep and wide tread block pattern for SUVs to handle various tough road conditions. Mud-terrain tyres are specifically for off-road use, while HT or Highway terrain tyres are usually road-biased tyres. If you live in high-rainfall areas, it’s better to choose a tyre which has deep grooves in the tread for better water drainage and road grip on wet roads. Also read: Buying alloy wheels for your car: A CarToq Guide
Tubeless or tube type
These days most cars come with tubeless tyres, which have a number of advantages over tube-type tyres. A tubeless tyre is less likely to lose air faster in a puncture and hence is more reliable. One can just fill air and drive for a bit, till the puncture can be fixed, as the nail / thorn acts as a temporary plug. They also generate less heat as there’s no friction inside between the tube and the tyre.
Size of the tyre
Ideally, when buying new tyres, stick to the car manufacturers recommended size. Usually this is the size provided on the top-most variant of the model of car that you have. But if you want a bigger size, don’t go over the limit, as a larger tyre will affect the odometer readings on your car as well as affect handling adversely. Always reduce the tyre profile size for each increase in tyre width size that you undertake.
For instance, the standard tyre size on a Mahindra Scorpio is 235/70 R16, where 235 is the width of the tyre in mm, 70 is the profile or sidewall height in percentage to the width of the tyre, a R16 denotes a 16-inch wheel rim diameter. If you want to increase the width of the tyres, the ideal upsize is 255/65 R16. Because even though the width has increased, the decrease in sidewall profile keeps the overall diameter intact.
The formula to calculate wheel diameter in inches is:
{[Width of the tyre x (profile number/10)] x 2} divided by 25.4 and add this to the wheel diameter in inches.
In the above example, the overall diameter of the Scorpio’s wheel with original factory-fitted tyres is 28.95 inches. When you upsize to the fatter 255 width tyres the overall diameter is 29.05 inches. As long as the difference is within 3% of each other, it is fine.
Thicker tyres are good for bad roads but will give poor handling as they have more flex and the car is not as sure-footed. Low-profile tyres are great for handling and precise control, but can be hard on the car’s suspension.
Tyre specifications
When buying new tyres, there are a few things you have to watch out for in terms of the specifications of the tyre.
Don’t put two different tyre sizes on the same axle (eg. a 235/70 R16 and 255/65 R16 on the left and right rear wheels respectively).
Ideally, all four tyres on the car should be of the same tread pattern and brand if possible for the best ride and handling.
If you have to mix tyres, ensure that the best two tyres are put on the front wheels of the car in most cars that are front wheel drive, as these tyres will have to pull the car, take care of steering duties and take the majority of the car’s weight on braking. On rear-wheel drive vehicles and MUVs ensure that the best two tyres are on the rear axle, as these bear most of the load and take care of driving duties (also in slippery conditions, they will tend to skid less).
When buying tyres, check the manufacturing date on them. Tyres that have been stocked with a dealer for over six months or more, will begin to harden and become brittle.
If all tyres are of equal age, ensure you rotate them every 5000 km. Undertake wheel balancing and alignment also every 5000 km to ensure the best life for your tyres.
Stick to the recommended tyre pressure and remove pebbles and materials stuck in the tread regularly to increase the life of the tyres.
Share any more tips you have on buying new tyres for your car.
