So what exactly is it?
From November last year, all tyres for sale must now be labelled in a similar manner to the picture at the top of this post, showing how a tyre performs in three different categories. These categories are:
- Fuel efficiency
- Wet weather braking
Taking fuel efficiency first: A is the best mark, meaning a set of tyres marked “A” should give slightly more miles per gallon than a tyre marked “B” or lower. According to Continental, a car fitted with tyres marked “B” should use approximately 1/2 a gallon of fuel less, over a distance of 625 miles, than the same car using “E” rated tyres.
With wet weather braking, a similar system applies. A tyre marked with an “A” will stop, from 50 miles an hour, up to 18 metres before the same car fitted with “F” marked tyres.
Then there’s noise:
A decibel (dB) is a “relative” measurement of how noisy something is. 0db is defined as the threshold of human hearing, i.e. it equates to the smallest change in air pressure you can hear. Everything else you can hear is louder than this.
For every additional 10dB, a noise is considered to be twice as loud, relatively speaking. A quiet room is generally considered to be around 30dB relative to 0dB, a normal conversation 40-60dB and standing next to pneumatic drill about 100dB.
But why would anyone take into account tyre noise when making a tyre purchase?
Modern tyres now offer so much more performance than they did even as little as ten years ago. With the advent of low profile tyres, and different compounds for winter, summer or sports use, tyre noise has now become a lot more intrusive than it used to be, to the extent that some drivers find it distracting.
So for the best performance, choosing the best tyre should be easy enough by simply looking for one with two “A” ratings? Unfortunately, this is not the case, for several reasons:
- The main characteristics that make a tyre fuel efficient, are the polar opposite of what makes a tyre grip well.
- Wet braking in a straight line tells you nothing about cornering or dry grip, aquaplaning resistance or braking in a curve
The ratings on the label obviously have their limitations, but at least now they do make it easier to compare the apparent performance between two different brands of tyre, where previously there was no information at all. A consumer can now walk into a tyre centre and make a more informed, and balanced decision about what tyres they want fitted to their car.