|Saturday, March 22, 2003||
FOR those of us who pay attention to road signs, "one way only" applies to roads. It’s a very important sign and is designed to allow traffic to flow smoother and with a greater degree of safety.
This now applies to tyres. The newest breed of tyres in the market is designed to run in only one direction, forward. This makes a lot of sense, since most of the time the car is in forward gear. These new tyres that are in the market are Potenza G III by Bridgestone. Curtis by Michelin and Ventura manufactured by Goodyear.
The reason for this new
design is quite simple. The inside tread on a tyre does not perform the
same function as the tread on the centre or the outside of a tyre. Hence
the different patterns. As a result of these different tread patterns,
the tyre becomes asymmetrical as it can perform in one direction only.
Other than when we are reversing out of our garage or driveway at home
or at a parking lot in the city, we are always in forward motion. So,
now we have tyres that are dedicated to provide maximum traction while
in forward gear and at speeds where road holding, cornering, braking and
accelerating are of primary importance.
One of the primary functions of these new treads is to drain water from the tyre grooves or sipes. A very serious problem with handling cars at high speeds during the monsoon season when the roads are waterlogged is aqua-planning. This was a common occurrence with the old tyre tread patterns.
Aqua-planning is a term applied to describe a condition when water forms a thin layer of water in between the tyre and the tarmac. The car is riding on a film of water. This gives the tyre no grip on terra- firma. It leads to a complete loss of control of the car.
The manufacturers claim that these tyres provide a smoother and quieter ride. If the new tyres perform incredibly well on wet roads then they are outstanding on dry roads too. The tyres are ‘H’ rated, which means that they are good for sustained speeds of 210 km ph or 130 mph. It is a common fallacy that these tyres are not suited for the Indian road conditions. Not true. These are radial tyres and, traditionally, these tyres are longer lasting because they are tougher than bias-belted or diagonal tyres. In a radial tyre, the cords run from bead to bead in a radial manner. They could be steel belted or made of nylon or polyester to give them extra strength.
If you have a set of these new tyres, get used to the fact that they are uni-directional. They will perform in one direction only. It is important that they be mounted properly in the direction of rotation. You should use a shop that has equipment to mount tyres on your rim without resorting to a hammer and tyre lever.
Tyre manufacturers have confirmed time and again that the maximum damage to your tyre is caused by the puncture-wala, the one with only a hammer to remove and fit tyres on a rim. Avoid him. Your tyres are expensive and sensitive equipment. Buy the best and look after them.
The Goodyear Ventura tyre has the following advice printed on the tyre: "Only specially trained persons should mount tyres."
The following are some tips to ensure a long life of your tyres and provide safety for your family.
Always maintain the correct tyre pressure as recommended by the manufacturer. Check tyres every 15 days.
All five tyres should be balanced — not just the front tyres. Keep your alignment correct and rotate tyres regularly.
In the past it was a common practice to turn a tyre on the rim in case of uneven wear. This will not be possible with uni-directional tyres.
Pay attention to the T.W.I (tear wear indicator). Worn- out tyres are an invitation to disaster. Replace tyres on time.
If you buy new tyres, buy new tubes. Old tubes in new tyres are a bad combination and not recommended. Also the tyre size and the tube size should be the same.
It is not recommended to use oversized tyres in your vehicles. They may do something for the looks of your car but they will retard the performance of the car.
A visual inspection of the tyres is important. Check for cuts, bruises, uneven wear. Ensure that the wheel nuts are tight.
Do not use radial tyres and bias tyres on the same axle. If you have radial and non-radial tyres (why should you want to do that?), the radial tyres should be on the rear axle. Ideally all four tyres should be of the same make and tread.
Much has been said about tyres but what about the importance of rims. Tyres are only as good as your rims. A rusted, bent or damaged rim may not hold the tyre securely. A bent rim will make balancing difficult. It may also destabilise the car.
In short, your wheel — comprising the tyre, tube (if you have one) and rim — requires constant attention.
What does 175/70 R 13 80 H mean? 175/70 is the cross-sectional height upon the cross-sectional width or the aspect ratio which is the distance between the rim and the road. It is in millimetres. R implies radial construction. 13 is the rim size. It is in inches. 80 is the load index i.e. how much weight each tyre can bear. 80 means 450 kg per tyre. H is the speed rating. H means the tyre is good for 210 kmph of sustained high-speed driving.