Reproduced from Autocar 28 january 2009

T h e o r i g i n a l c a r w e e k ly

Cheap tyres the real cost Tyre Test highlights safety concerns

Cheap imports | Tyre test 2009

cheap tyres

the real cost Is bargain rubber from the Far East really a shrewd investment? We have our doubts after testing five of the leading low-cost options STORY JAMIE CORSTORPHINE, keith howard PHOTOGRAPHY STUART PRICE

Our man was stunned by Contis’ advantage over the ‘bargains’

T

yres are a distress purchase for many car owners, so when the time comes to replace them it’s no surprise that many motorists shop on price. But by buying cheap tyres, are you sacrificing primary safety? We heard from our hosts at Continental Tyre’s Contidrom test facility last year that they had tested cheap Far Eastern imports and got some scary results. At the time we thought this was interesting but probably not of huge significance, because of low sales volumes in the UK. Wrong. Accurate official statistics don’t exist, but cheap import tyres from China and Taiwan account for around a fifth of all passenger car tyres currently sold, many of them via the internet. That makes their performance well worth testing. In order to earn the circled ‘E’ on their sidewall, tyres have to pass the ECE R30

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high-speed test, which ensures they can carry a specified percentage of their rated load at close to their rated maximum speed without failure. But there are no statutory tests of braking, handling or aquaplaning performance, and even the R30 test is considered inadequate by many car makers. In other words, just because a tyre can legally be sold in the UK, that is no guarantee of its performance in safetycritical aspects of normal driving. So just how capable are cheap import tyres from China and Taiwan? We chose a popular tyre size – 205/55 R16 – and returned to Contidrom with a Golf 1.9 TDI to find out by pitting five brands (GT Radial, Linglong, Nankang, Triangle and Wanli) against Conti’s own Premium Contact 2. The imports were all purchased in Germany and the Contis were selected at random from a distribution centre. The results were an eye-opener. ◊

how and where Continental’s Hanover test facility — the Contidrom — proved such a success on our 2007 test that we could think of no better place for this year’s action. With a 2.4-mile dry circuit, 1.1-mile wet track and objective test areas, the Contidrom is one the world’s most advanced tyre test facilities. Unlike in previous years, where we used two test cars (one front-wheel drive, the other RWD), in testing budget tyres we opted for just a front-driver. We chose VW’s Golf 1.9 TDI as the ideal example of a typical family hatchback. Crunching the numbers (on his ninth tyre test) was Keith Howard, and in the driving seat was Jamie Corstorphine.

CONFIDENCE INTERVALS

Because lap times and braking distances for each tyre are not exactly the same each time you measure them, we use standard statistical methods to calculate the confidence intervals shown in the charts. We can be 90 per cent certain that had we repeated each test a very large number of times, the true mean (average) would have fallen within this range. Each tyre is scored according to how many others it beats in each test. The scoring system is six points for the test winner, five points for second best and so on. In the case of a tie, the points for the tyres’ places are divided equally between them.

Howard’s laptop nearly melted when it came to the wet handling results

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Tyre test 2009 | Cheap imports

Wet Handling On average, it rains 200 days a year in the UK. Which makes having a tyre that works well in wet conditions a priority and the wet handling test one of the most relevant that we conduct. The results make for disturbing reading. Our Golf is hardly the last word in performance – its 104bhp is barely enough to break traction, even out of the tightest hairpin – and the wet circuit is not tremendously long (a lap takes around one and a half minutes), yet the difference in time between the Chinese tyres and the Continental is staggering. Equipped with the best-performing Chinese tyre, the Nankangs, the Golf was three seconds a lap slower than with the Continental, but with the worst, the Triangles, it lapped a scarcely believable eight seconds slower. An eight-second gap in something as humble as a diesel Golf is all the evidence you could ever need that tyres matter, not only in terms of lap times but also in how quickly you can stop or turn when it really matters. Wearing the Contis, the Golf felt more agile, stopped quicker and steered with more feel than with any of our five Far Eastern brands. The Nankangs not only produced the quickest lap time but also got closest to the Contis in terms of feedback. They produced less outright grip than the control tyres,

WET HANDLING Confidence interval

Continental

1st

Nankang

2nd

GT Radial

=3rd

Wanli

=3rd

85

Linglong

5th

Triangle

6th

86 Better

87

88

89

90 91 92 Lap time (sec)

93

94

95

96 Worse

97

but the balance between front and rear grip was even, while the fall-off in grip was predictable and gradual. Swapping to the GT Radials lost another eight-tenths of second, but this doesn’t fully explain how different the Golf felt. Gone was the balance, replaced by an awkward yo-yoing sensation as the car slipped first from the front and then the rear. Although the GT Radials didn’t struggle for traction, under braking and in mid-corner they had markedly less grip than the Nankangs, and it fell away with little warning. While the Wanlis proved slower again, subjectively they felt more stable, balanced and communicative than the GT Radials. The grip levels were actually lower, hence the slower lap, but it was easier to comfortably work the car up to the limit and the resulting slip was more controllable. Put simply, the Linglong and Triangle were in a different, much lower league, and they both recorded similarly poor lap times. Although the Linglongs provided good steering feel and balance, the shortage of grip was truly staggering; the sensation was not unlike driving on ice. This caused an issue not only through the corners but also under braking and under power. But the wooden spoon goes to the Triangles, not only for recording the slowest lap but also for providing the least satisfying drive by some margin. Their main downfall was an inability to deal with longitudinal and lateral forces simultaneously. Touch the throttle mid-corner and the Golf would slip wide; brake in anything but a straight line and the ABS came juddering in. The resulting lap was not only slow but also scrappy and inconsistent. To get a handle on the gulf in ability, consider that in one 50mph corner the Triangles were 8mph slower and generated 0.2g less. That might not sound like a lot, but it could be the difference between staying on the road and leaving it. ◊

Conti rubber was a full eight seconds quicker than the Triangles

Rail-guided Audi A4 was used for straight-line aquaplaning tests

WET BRAKING

WET CIRCLE

AQUAPLANING (LONGITUDINAL)

Confidence interval

Confidence interval

AQUAPLANING (LATERAL)

Confidence interval

Continental

1st

Continental

1st

Wanli

=1st

Continental

Nankang

2nd

Nankang

=2nd

Continental

=1st

Wanli

2nd

GT Radial

=3rd

GT Radial

=2nd

GT Radial

=3rd

GT Radial

3rd

Wanli

=3rd

Wanli

4th

Linglong

=3rd

Linglong

4th

Triangle

5th

Linglong

=5th

Nankang

5th

Triangle

5th

Linglong

6th

Triangle

=5th

Triangle

6th

Nankang

6th

30

32 Better

34

36 Braking distance (m)

38

40

42 Worse

We hooked up an adapted Audi A4 to Contidrom’s rail-guided system for the wet braking test. The braking distance is measured from 80-20km/h (50-12mph) on an asphalt surface and then extrapolated to zero to eliminate ABS inconsistencies at low speeds. Seven runs are made and the highest and lowest results eliminated for the analysis. The difference between the best (the Conti) and the worst (the Linglong) was 8.5m. It would probably have been even larger had the test been conducted on a lower-friction surface.

0.40

0.45 Worse

0.50

0.55 0.60 Lateral acceleration (g)

0.65

0.70 Better

This is a test of cornering grip in the wet, in which the test car (a specially instrumented Audi A4) is driven as fast as possible around a wet asphalt circle of 50m diameter. Seven laps are timed, the fastest and slowest eliminated, and times for the remaining five laps then converted into lateral acceleration in g. The Conti walked this test, pulling 28 per cent higher lateral acceleration than the Triangle; that’s equivalent to a 13 per cent difference in cornering speed. Unsurprisingly, the correlation with the wet handling results was very close.

40

42 Worse

44

46 48 Critical speed (mph)

50

52

54 Better

This test is also conducted using the rail-guided system, but with the car’s left wheels running in a water depth of 7mm. As the car enters the standing water, the driver accelerates and the instruments record at what speed the driven left wheel reaches a slip ratio of 15 per cent. The higher this speed, the better the aquaplaning resistance of the tyre. It was surprising that the Wanli tied with the Conti here — but then its tread pattern is lifted from the Dunlop SP9000. The rest, particularly the Triangle, performed poorly by comparison.

0.24

0.26 Worse

Confidence interval

0.28

0.30 0.32 0.34 0.36 Residual lateral acceleration (g)

0.38

1st

0.40 0.42 Better

This test is conducted on a large asphalt circle with a radius of 200m. Around it is a 20m long by 5m wide section of standing water, with a depth of 6mm. The test begins at a speed of 55km/h (37mph), which is increased in 5km/h (3mph) increments to 95km/h (59mph). Lateral acceleration through the water at all the speeds is averaged; the higher this figure, the better the tyre resists aquaplaning during cornering. Tread compound is a factor in this test, so the Wanli couldn’t match the Conti. The worst tyre in a deep mid-corner puddle was the Nankang.

Contis offered better wet lap times as well as far more feedback

The wet handling circuit exposed huge gaps in the tyres’ abilities

Extra dose of bravery pills was required for some of the flying laps

‘The difference in time between the Continentals and the Chinese tyres on the wet handling circuit was staggering ’

Cheap imports | Tyre test 2009

DRY Handling The spread of times for the dry circuit was much narrower than for the wet, at 2.6sec between the Contis and the Linglongs, but the subjective differences were big enough. Again the Nankangs came out top of our budget tyres; they ran the Contis very closely, and on one lap they even posted a quicker time. The Nankangs’ most striking characteristic was how iron-fisted they felt, giving the Golf a safe, solid feel and meaty steering. However, the Nankangs couldn’t match the Conti’s delicate, balanced feel, which allowed the Golf to be worked through the more demanding corners. If we turned in with too much speed, the Nankangs gave no option apart from getting completely off the throttle and sacrificing speed – hence the variation in lap times and the slower average. The GT Radials produced the next quickest time, 0.6sec behind the Nankangs. While the outright grip produced was not far off that of the Contis, the fall-off in grip was more sudden and the steering was uncommunicative. The GT Radials needed to settle momentarily before delivering full grip; similarly, if you suddenly backed off the throttle mid-corner, there was a lot more movement from the rear end. The Triangles produced reasonable outright grip but became spiky near the edge of adhesion. In particular, once front-end grip had been breached the Triangles understeered wider and more suddenly than with any of the quicker tyres. In lift-off situations they produced some (acceptable) rear movement. Wearing the Wanlis, the Golf felt like a different car, with noticeably less grip, more movement through the direction changes and more throttle control required to keep the car on line. The Wanlis also struggled under braking, with less initial bite and greater ABS intrusion. That they almost matched the Triangles’ time is down to a linear, predictable fall-off in adhesion. ‘Soggy’ and ‘unresponsive’ are two words to describe the Linglongs. We could point to the traction problems exiting the hairpin, or the tendency to drift wide under power through long corners. But the biggest issue was instability turning into faster corners. Be anything but super-smooth and the Golf could slide quite sharply from the rear, often requiring opposite lock in 80mph-plus corners. On a test track it was entertaining, but you wouldn’t desire it for road use. ◊

breaking Aggressive behaviour with the Linglongs was rewarded with the rear end

DRY HANDLING Confidence interval

Continental

1st

Nankang

=2nd

GT Radial

=2nd

Triangle

=4th

Wanli

=4th

Linglong 107

away, often at speeds of more than 80mph.

This was fun on the test track, but you wouldn’t want it on a B-road

One in five new tyres sold in UK is ‘cheap rubber’ from the Far East

‘The biggest issue with the Linglongs was instability turning into faster corners’

=4th 108

109 110 Lap time (sec)

Better

111

112 Worse

DRY BRAKING Confidence interval

Continental

1st

Nankang

2nd

GT Radial

=3rd

Triangle

=3rd

Wanli

=5th

Linglong 36

37 Better

=5th 38

39 40 41 Braking distance (m)

42

43 44 Worse

Dry braking is measured at Contidrom on an asphalt surface from an initial speed of 110km/h (69mph), with the braking distance recorded from 100km/h (62mph) to rest. Seven runs are made on each tyre, and the highest and lowest results are eliminated to leave five runs for the analysis. This test usually results in a close grouping; last year the distance between best and worst was a little over three metres. But this year the winning Conti stopped a full 5.5m shorter than the last-placed Linglong. With Linglongs fitted, the test car was still doing more than 20mph at the point where the Conti had stopped.

HIGH-SPEED TESTS

GT Radial rubber failed VW’s specified tyre tests

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Many car makers consider the mandatory ECE R30 high-speed test to be inadequate and specify procedures of their own in which the load or maximum speed are raised, the inflation pressure dropped or the camber angle increased. Our five import tyres were tested at Conti’s engineering HQ according to VW’s requirements, which all original tyre fitments on its cars have to pass. Four of the five (GT Radial, Linglong, Nankang and Triangle) failed the test because of structural failure, the most dramatic being that of the GT Radial (left).

Far Eastern tyres were more at ease in the dry, but still not great

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Corstorphine gave the Linglongs a fair stab under wet braking…

This scene was replicated around 200 times during our tyre test

…but the result was similar to a bad chase scene in The Sweeney

Time to crunch numbers: Corstorphine and Howard hit the data

A humble Golf TDI was our unglamorous assistant for the day

VERDICT We were expecting the bargain tyres in this test to fall short of the Continental reference rubber, but we weren’t prepared for just how wide the gap was. The Conti easily topped the final rankings, but there was little good news below it. Best of the rest overall was the GT Radial, because of its consistent performance. But a wet lap time 3.4sec adrift of the Conti’s indicates just how far even it fell short. And remember, other premium tyres may be superior to the Conti; that was certainly the case in our test last year. In many of the disciplines the Nankang was closest to the German tyre, but poor performance in the two

aquaplaning tests dropped it down to BRAKING Best and worst wet braking distances from 50mph third position overall. 31.7m Continental With its tread pattern copied 20 25m 30m 35m Still doing 27.8mph Linglong from Dunlop, the Wanli performed well in the aquaplaning tests. But it TRACK GRIP Speed differential between best and worst on wet circuit was less competent elsewhere, Speed (mph) notably in the dry braking, and 65 dropped to fourth. 60 Continental Little that’s positive can be said 55 about the Linglong and Triangle, which 50 45 posted greatly inferior results. Ask 40 Triangle yourself: on a wet road in particular, 35 30 would you like the car behind (let 25 alone your own) to be fitted with a 20 state-of-the-art premium tyre or a 15 10 cheap import? Having seen how the 5 cut-price tyres in this test performed, 0 0 500 1000 1500 2000 2500 3000 we’re in no doubt about our answer.

Left turn

Acceleration

Longitudinal acceleration (g)

Braking

0

0.5

Wet braking: Linglong-shod Golf was still doing 27.8mph at the point where it had stopped on Contis…

‘We were expecting the bargain tyres to fall short, but we weren’t prepared for just how wide the gap was’

1.0 1.0

0.5

FINAL RESULTS Prices supplied by blackcircles.com (0845 620 2000) and include valve, fitting and balancing

Right turn

0.5

0

0.5

Lateral acceleration (g)

3500

Distance (feet)

CORNERING Lateral/longitudinal g-forces on wet circuit: Conti (blue) vs Triangle (red) 1.0

40m 40.2m

1.0

PRICE

DH

WH

DB

WB

ALo

ALa

WC

TOTAL

Conti

£75.83

6

6

6

6

5.5

6

6

41.5

GT Radial

£58.65

4.5

4

3.5

3.5

3.5

4

4.5

27.5

Nankang

£55.20

4.5

5

5

5

2

1

4.5

27

Wanli

£51.41

2

3

1.5

3.5

5.5

5

3

23.5

Linglong

£52.44

2

1.5

1.5

1

3.5

3

1.5

14

Triangle

£51.06

2

1.5

3.5

2

1

2

1.5

13.5

Key: DH = dry handling; WH = wet handling; DB = dry braking; WB = wet braking; ALo = aquaplaning longitudinal; ALa = aquaplaning lateral; WC = wet circle Thanks to Eurotunnel (www.eurotunnel.com, 08705 353535)

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4000

www.conti-online.co.uk

When you really need to stop. Full stop.

Ty r e s

March 200

8

ContiSportContact 3 225/45 R17 Y