It is important to keep an eye on your tyres because they need to be in a sound, roadworthy condition at all times. This is not only so that you won’t get fined in a traffic police inspection, but also for your own safety (and everyone else’s). Overly worn tyres give you less control and a poorer grip on the road, as well as increasing the risk of aquaplaning in wet conditions. It takes much longer to stop when your tyres are worn, and you could even be at risk of a blowout.
If your tyres do not have an obvious damage on them, you might be wondering, how you’d tell that they are due for a change. Well, tyre manufactures place an indicator called Tread Wear Indicator (TWI) on the tyres to help motorists find the absolute time to change their tyres.
Tread-wear indicators are projections within the tread grooves designed to give a visual indication of the degree of wear of the tread.
Why do we need TWI?
In a perfect world, like a perfectly dry road, tread actually reduces a car’s performance because it has the effect of reducing the contact patch area, and the forces that can be transmitted through the contact patch are correspondingly reduced.
But in a not-so-perfect world, on a wet road, the tread is vitally important. The tread is designed to disperse water from the contact patch, thereby helping the tyre grip the road. Without tread the tyre’s ability to grip a wet road is severely limited, making it almost impossible to stop, turn, accelerate and corner.
How to use TWI
All tyres have “TWI bars” in the main grooves and “TWI mark” on the shoulder region at regular intervals around the circumference of the tyre. They indicate when a tyre is worn to its limit of safety. Different manufacturers use different marks / symbols to indicate TWI.