Picking the tyre that will work best for you
OUR tyres are tested in nine disciplines, covering wet and dry assessments, as well as cabin noise and rolling resistance.
In each test, the results are converted into percentages to provide an accurate reflection of the performance differences. These percentages are then added together, with the wet tests forming half of the results and the rest making up the remaining 50 per cent.
The only weighting we do is for price (which has a small role to play in our safety-focused test) and to ensure that assessments where the differences between the best and worst performers are large, such as aquaplaning, count the same to the overall result as those where the gap in performance is small; in dry handling and cabin noise, for example, there can be less than three per cent separating the top and bottom of our tables.
Wet tests
TYRE labelling just measures braking in the wet. We do, too, but we also assess cornering, handling and how a tyre copes with deep water at speed.
You’d never know it at first glance as the surroundings are radically different, but the 1.8km Uvalde wet handling track is a recreation of the one at Continental’s Contidrom facility near Hanover, Germany, where we’ve completed hundreds of laps in previous tests. Even the tarmac was shipped from Europe to ensure comparable results. So there’s the familiar mix of fast direction changes, hairpins that test traction and longer sweeps that reveal a tyre’s balance. An average of lap times provides the result.
Alongside is the 55-metre wet circle which measures a tyre’s pure lateral grip without aquaplaning coming into play. You don’t want a big breakfast before tackling this as you tuck the nose of the car close to the inner kerb, fix the lock then accelerate until the line can’t be held, repeating up to 10 times. Again, average lap times give the result.
Wet braking is measured from 50mph to a stop using a rail system. A hefty bar is bolted across the front of the car, with a shoe clamping to the rail. The car is accelerated – no need to steer – until just over 50mph before braking. The distance is measured and an average of up to 10 runs taken to get the result.
We use the same rail for straight aquaplaning. The car is accelerated with one wheel in the water. Electronics measure the difference between the driven wheels until one is spinning more than 15 per cent faster than the other and the speed recorded. Again, an average is used.
For the curved aquaplaning test, the car is driven through a flooded section of a 200-metre circular track at ever higher speeds. Lateral grip is measured until all grip is lost.
Dry tests
SINCE our last test in Texas, Continental has opened its new dry handling track, and it’s a massive improvement on its predecessor. Out of flat scrubland the designers have created a 2km track with elevation change, off-camber turns and a challenging series of highspeed direction changes. There’s also a long, high-speed curve which tells you all you want to know about a tyre’s balance. We took an average of lap times to decide the winner.
The three-mile oval is used for the brake test because it provides plenty of time for brakes to cool between stops. We performed a series of stops from 62mph and measured the distance taken.
Cabin noise
THERE’S no direct link between passby and cabin noise, so if you’re after the quietest tyres when you’re behind the wheel this is the test you need.
We coasted down from 50mph over three surfaces on the three-mile oval, using a sound meter to rate cabin noise. This was done twice and an average taken from each surface – rough tarmac, smooth asphalt and concrete – to get our final verdict.
Rolling resistance
THIS is key to fuel economy and the reason why it’s part of the tyre labelling legislation. Rolling resistance measures the force needed to turn a loaded tyre.
We used an average of results from two tyres, with all tests carried out to industry standards. Roughly speaking, a difference of around five per cent in rolling resistance will mean a one per cent change in fuel consumption.
Price
OUR test-winning online tyre retailer Blackcircles.com supplied our figures, which are fully fitted prices. They are what it charges or what it would do if the tyre is not currently part of its range.
IT has been more than 10 years since Avon featured in our tyre tests, even though the Cooper-owned British brand has been invited. We hope this result won’t mean another decade passes before it returns because there are few positives in these results; its ZV7 trailed rivals in most tests and was some way behind the next best overall.
The high spot was a win in the cabin noise test, where it proved effective at damping the roar over rough concrete. It was also among the quietest over the tarmac. But elsewhere there’s work to do.
We’ve often seen label ratings at odds with our results, but none as stark as this. While the Avon has the top A wet grip rating, it finished last behind tyres with lower grades. Label ratings are established in optimum conditions and obviously the Texas heat didn’t suit the ZV7. It needed just under seven metres more to stop in the wet than the pacesetting Pirelli; when that tyre had come to a halt, this was still doing 25mph-plus.
Around the wet circuit it felt secure with little rear movement, but didn’t have the same grip as rivals. It was a similar story on the wet circle. It fared little better in the deeper water of the aquaplaning where it just managed to beat the Pirelli in the lateral test.
In the dry the tyre felt soft, although the balance was good. But the lap times were not there; it was more than a second off the leading pace.