E I G H T TESTS
Looking for rubber with soul? Or just a great blend of grip, progression and longevity? We’ve done the hard yards – and the exhaustive testing – to guide you through the black hole that is tyre choice…
POPULAR perception suggests that the average consumer considers tyres a ‘grudge purchase’, often enquiring “Which is the cheapest?” at the sales counter.
Hearteningly, however, Wheels’ tyre industry sources say that enthusiast buyers are more likely to have an idea of what they want, and are generally prepared to pay more for a tyre that offers a superior level of safety and performance.
That’s great, but the challenge is identifying the best tyre. How do you do it, beyond choosing one from a brand name, with a higher price tag?
That’s where the Wheels Tyre Test comes in, with a series of tests designed to sort the grippy from the slippy.
Our testing program was held on the skid pan and skid circuit of Sydney Motorsport Park over two days – dry testing on day one and wet testing on day two.
Race driver and engineer Renato Loberto drove the Hyundai i30 for each ‘blind’ test – he didn’t know which brand was fitted to the car.
Each set of tyres was put through the same regime. A public road loop kicked off each test, serving two purposes: to scrub in the surface of the tyre and provide the opportunity to take a tyre noise reading on a section of coarse-chip road. Back on the skid pan, Renato hit the slalom, cornering test and brake test (in that order) before taking to the skid-circuit for a series of hot laps.
On the second test day, we repeated the slalom, cornering and braking tests with the skid pan’s irrigation system set to wet, for a total of eight test disciplines.
Each discipline was scored out of 10 with the exception of the noise test. So, 20 points for the slalom tests (dry and wet), 20 points for the cornering tests and 20 points for the braking tests, plus 10 points for the skid circuit hot-lap and five points for the noise test.
The winner at each discipline took the full tally of points, while the rest of the tyres were prorated based on their proximity to the winner.
Totals were out of 75 points, but we’ve presented them as percentages for clarity.
Tyre temperature was noted before each run and a control tyre run was completed at the beginning, middle and end of the day to ensure that potential variables such as vehicle performance, water coverage (on day two) and track temperature weren’t evolving as tests went on.
The Hankook control tyre is the definition of an OEM touring tyre (it’s fitted standard to the Hyundai i30), which is what we sought from each of the competitor brands. We say sought because identifying tyres of the same nominal performance level, from different brands, is perhaps easier said than done.
Although we’ve chosen a particular 16-inch tyre – because it’s a popular seller – the tyre models represented are available in a range of other sizes, and our results are applicable to each of them, too.
NINE tyres lined up for the 2015 Wheels Tyre Test, plus the Hyundai i30’s standard-fitment Hankook Kinergy Eco as a control tyre. We selected the size (205/55R16) as it’s the second-best selling tyre in Australia and is commonly fitted to many equally strong-selling small cars. (It was also, a long time ago, the exotic standard fitment on the front of the Porsche 911). Our test subjects are all touring tyres of the sort a small-car owner on a moderate budget might fit as replacements for their wornout OEM tyres.
THE brief for the official Tyre Test 2015 car was a small car that comes factory-fitted with 205/55R16s and provides confident, predictable handling. We didn’t want a dynamic dud that would colour the results with its chassis shortcomings, and we needed to be able to turn the stability control off, so the results weren’t recorded with the help or hindrance of the car’s electronics. The i30 was just that car, and Hyundai Australia supplied two of them, as well as spare brake pads and wheels. As it turned out, we didn’t need the pads, or the spare car; the i30 performed more than 100 slalom runs, cornering test laps and brake tests without complaint.
WHEN he was growing up in suburban Brisbane, one of Renato Loberto’s primary school teachers told him he “should be a racing driver with a name like that”. He said “okay” before demonstrating inherent speed in his first open-wheeler foray at a wet Lakeside Raceway, in which he climbed from P35 to eighth.
A motorcycle accident in 1999 put his motorsport career on hold, but he emerged with an engineering qualification. Then, in 2002, his motor racing was again put on hold when he was diagnosed with testicular cancer, from which he made a full recovery.
In 2004, Renato combined his wheelsmanship, technical nous, work ethic and all-round goodblokeness to start MotoKinetic, which offers services from automotive event management to race driver coaching and car set-up and analysis. He stood on the podium at this year’s Bathurst 12 Hour and jetted to a job at Imola, Italy, after our Wheels Tyre Test, which must have been quite a come-down.
THE tireless and endlessly cheerful team from JAX tyres – with equipment and expertise lent from Eagle SMF Tyre and Automotive Equipment – turned a pair of Sydney Motorsport Park pit garages into a tyre shop in the blink of an eye, and they fitted, balanced and swapped sets of wheels and tyres with F1-like pit stop speed.
The Wheels Tyre Test involved stripping and fitting some 25 sets – 100-odd tyres in total – and it was all in a day (or two’s) work for the team. Thanks, fellas, we couldn’t have done it without you.
TYRE Test logistics and numbers man Jimmy Whitbourn (left) is also your author, which means he wrote this in the third person, which is something the 35-year-old Sydney freelance motor-noter lists as a favourite hobby, along with whitewater rafting, long walks along the beach and drinking cab sav. A decade ago, Jimmy, a mechanical engineer, jacked in a promising automotive design/manufacturing career to climb on board the supercar-paced show-biz ride of working at Wheels. As it happened, one of his first jobs was buying the lunches for the Wheels Tyre Test.
Clearly, he’s never recovered.
THE slalom is a defensive driving course staple, but its inclusion in our test regime serves to subject each tyre to the kind of swerve-and-recover punishment it would experience on the road when car and driver are faced with an errant pedestrian or vehicle in their path. It’s a tough test, and a tyre that can dispatch it confidently is a safe one. The slalom consists of four cones spaced 18 metres apart, which neatly packages three changes of direction into a single, sub-four-second test.
Entry speed through the start gate is 70km/h – deviations in speed or a collected cone result in the deletion of the run, which is Driftbox-logged for lateral g. The electronic stability control was switched off for the tests – we weren’t testing the i30’s ESC system – and the attitude of the car provided a visual snapshot to go with the data. Time is the measure of performance in the slalom and the 10-strong field saw results ranging from 3.08sec (Toyo) to 3.32sec (Momo) with a median of 3.20sec.
That puts the quickest tyre eight percent ahead of the least-quick.
THE Toyo bolted out of the gate with a solid initial result. In fact, the dry slalom was its sole first placing in any discipline. Two- to three-tenths behind it, the Michelin, Goodyear and Yokohama were quite close on times despite behaving quite differently. The Michelin gave “instant feedback” while the Goodyear felt like it improved subtly as it warmed up.
The Yokohama offered great turn-in and felt very solid in construction, resulting in direct steering response.
The dry slalom saw the Lassa tyre secure fifth. Though it was not very communicative, it had the grip to get through the cones quickly, which hinted at more surprise performances from the Turkish tyre.
THE cornering test, or ‘circle test’, measures steady-state grip. That is, the outright lateral grip of the tyres around a corner of a fixed diameter (18m). That corner is a circle marked out with cones and time is again the measure of performance in this discipline – the tyre that can hang on with the greatest grip can get round the corner most quickly. We logged two laps from each run, which consisted of four laps, including an initial one to get the car locked onto its limit of adhesion. In practice, this means building speed to the onset of understeer – not understeering; just before the front starts to slide. Peak lateral g was logged by the Driftbox, but our results are based on average g, which is a more accurate way to establish an order, taking spikes out of the equation. We calculated that average g figure from the lap time using the formula: 4 x pi squared x radius (m) / 9.81 x time (sec) squared. Sitting in the car next to Loberto as he lapped the circle gave a feeling for the surprisingly high speed and g of the test, which looks undramatic from outside the car.
The pro that he is, Renato did more than 350 laps without complaint or threat of losing his lunch.
SPOILER alert: The dry cornering test wasn’t the Continental ContiPremiumContact5’s only firstplace finish. The Conti put two-tenths between it and the second-placed Yokohama, which was 0.1sec ahead of the Michelin in third. The Conti looked – and was – tail-happy through the slalom, but this didn’t point to a performance deficiency. Loberto reported lots of front grip and a tyre that feels quite strong in the sidewall.
Why did the tail go? Turn-in was so sharp the rear couldn’t keep up and was thrown into a small slide. But the numbers supported the seat-ofthe- pants verdict. The Conti was the quickest round the circle, which meant it was generating the greatest grip – an average of 0.68g, which was 10.7 percent more than the least-grippy tyre.
TODAY’S cars make emergency braking really easy for the driver. Stand hard on the brake pedal and the ABS takes care of the rest. There’s nothing to it, other than not being daunted by the pulsing of the pedal and the noise of the ABS system, and not lifting off the brake pedal. That’s why a defensive driving course that lets you practise (or at least experience) hard braking is worth its salt, but we digress. We had a spare set of brake pads at the ready, but the i30 performed our repeated braketesting without so much as a hint that fade would set in. Loberto hit the brake pedal with all the subtlety of, well, a racing driver. So the braking performance variable was the tyres. The Hyundai passed the braking point carrying 80km/h, at which point the anchors were deployed. The brake test zone was marked with cones at 5m, which gave a quick visual guide to relative tyre performance. After the control tyre run, I positioned myself alongside the 27-metre mark for data recording duty. Whether I had to walk farther down, or back up, the braking zone for subsequent runs told me how good a tyre was, or otherwise. There was a 2.4-metre gap between the hard-stopping Michelin and the Goodyear.
THE Michelin Primacy 3 ST stopped the i30 in 25.3 metres on average, which was 20cm shorter than the next-best Yokohama, which pulled the highest peak, at 1.07g. The Michelin stopped a bit more than half a metre shorter than the third-placed Dunlop.
Tellingly, the Michelin and the two tyres behind it were significantly below the median stopping distance of 26.83 metres. This came about because, although the top five were within a metre of each other, even the best of the bottom five was close to two metres adrift of the eventual victor. Renato reckoned the Michelin feels strong in sidewall and surface, and was impressed by the Dunlop, which exhibited no tread walking [squirming of the tread blocks] at all.
THE skid circuit serves to show which tyre can bring together the qualities tested in each of the formal disciplines for a quick lap. It’s also a bit of fun for Loberto, who might otherwise go cone-crazy on the skid pan’s confines. Tyres that demonstrated good transient and steady lateral grip, as well as longitudinal grip in the braking exercise, looked likely to reel off quick laps around the figure-of-eight, but that wasn’t necessarily the case. In part, that’s because the circuit test introduces tyre temperature as a more significant factor. Asking the tyres to handle several ‘load events’ over a circa 24-second lap tells us what it would do on a mountain road, which might be quite different to what it does when dealing with a single swerve or stop in the city. We put a pyrometer on each of the i30’s tyres after each test – the rear right tyre was in the high 30s on average, while the front left was at 78deg on average, up to as much as 93.5deg in the middle of a 21-degree late winter’s day, which shows how hard it was working. The quickest laps were in the mid-23s and the least-quick in the mid-24s, and the fact Loberto reported some tyres ‘going off’ told us as least as much as the lap timer did.
THE Continental’s first place in the cornering test signposted its circuit test result. The Conti was 0.3sec quicker than the Toyo, but second, third and fourth were separated by hundredths, so you could really consider them to be equal second.
According to Loberto, the Toyo was “the best tyre so far”, but it was third in the running order, and the benchmark was subsequently reset by the Conti – “Best feeling so far, great initial turn-in and can lean on the tyre quite a lot” – and the Yokohama.
Interestingly, our wheelman reported that the latter had best turn-in feel of all tyres tested, but that its front grip levels reduced on each run.
IN A repeat of a phenomenon that occurred in the last running of the Wheels Tyre Test, the average time to complete the slalom was fractionally quicker in the wet than the dry. We couldn’t easily explain it then, and we can’t now, but it seems that the i30 is a tiny bit more agile in the wet. During some runs it certainly looked as though the tail of the car was coming into play more than it had been in the dry. We did say fractionally quicker, though – there were only three-thousandths in it. Despite that, the spread of times in the wet slalom was smaller than it was in the dry – 0.14sec versus 0.24sec. Tyres that were quicker in the wet than the dry included the Yokohama, Continental, Dunlop, Momo and the Hankook control tyre. The Roadstone recorded an identical average time in the wet as the dry. The Goodyear’s times were damn near identical, too – just one-hundredth slower in the wet. It was the only tyre to finish in the same spot (third) in both the dry and wet slalom tests, which earns it kudos for allweather consistency. The Momo proved the surprise package when the taps were turned on, climbing six spots to fourth, while the Michelin dropped from second to seventh.
WE HOPE we’re not giving too much away at this point, but the Dunlop emerged with its one and only first place by recording the quickest average time while also improving the most of any tyre in comparison with the dry results. Our steerer said it provided great turn-in and driver feedback, and that it gives plenty of warning before it slides. It was a similar story for the Yokohama in second place, which offered excellent initial turn-in with great awareness of the grip/slip threshold. While the Goodyear’s score was virtually identical to that of the Yokohama (just 0.0025sec slower), it was felt to offer relatively little skid warning.
TURNING on the skid pan’s sprinklers didn’t do anything unexpected to the grip level of the skid pan – the average overall lateral g generated on the cornering test dropped by three percent, which we’d expect on wet concrete. The kinetic frictional co-efficient of dry concrete is approximately 0.6 to 0.85.
Add water (a nominal depth of 3mm in this case) and that co-efficient drops to anywhere from 0.45 to 0.75. Despite that, just as in the wet slalom, some tyres managed to improve on their dry test result.
On the Toyo, Goodyear and Lassa tyres, it seemed Loberto found the i30’s neutral cornering state at a slightly higher speed in the wet than the dry because they all pulled higher Gs. The loser was the Toyo, which fell six places, while, just as in the wet slalom, the Michelin dropped down the order (four places). The other movements in the ranks were moderate, including a climb from fifth to third for the Dunlop. Its emerging rain-master status may have to do with the design and orientation of the drainage channels across the tread face. Meanwhile, at the top, the status quo remained.
LOGICALLY enough, the Continental ContiPremiumContact5 mustered less outright grip in the wet than the dry – about five percent less in round figures.
However, it still hung on tenaciously for the quickest average lap around the circle and a 0.649g figure that topped all other tyres in this discipline. This makes the Continental the outright slalom-test gold medallist, having topped the timesheet during the dry iteration, too. Like the Continental, the Yokohama, which took second place, is a great tyre in terms of its transient grip on both wet and dry surfaces. In the wet the Dunlop is just as good, though.
Its time, lateral g (and, therefore, score) were identical to the Yokohama’s, down to 14 decimal places.
ASK most tyre shoppers to tell you what’s important to them in a new set of hoops (other than price) and most will tell you they want good grip for braking, especially in the wet. The wet braking test, then, is the big one. Average stopping distance from 80km/h grew from 26.6 to 28.7 metres when the sprinklers soaked the skidpan – that’s 2.1m or eight percent farther. Worryingly, the Michelin, which had won the dry braking test convincingly, took an extra 4.9m to pull up in the wet, with Loberto reporting aquaplaning at all stages of braking, which resulted in inconsistent stopping distances. It could do better than its 30.18m average stopping distance – its best was 29.4m – just not every time.
At the other end of the results spectrum, the Lassa actually stopped better in the wet than it did in the dry, but that was partly because its dry stopping performance was relatively poor (it finished second-last). However, the results for the rest of the pack were more predictable. As the overall average suggests, most tyres weren’t quite as good in the wet as they were in the dry. But the best of the bunch stopped surely regardless of the moisture level…
THE Continental’s wet-braking gold medal result was its fourth across the disciplines, which might simultaneously ruin the suspense for the final test discipline (tyre noise) and the overall results. Then again, it might not… It’s a terrific result that the Conti could stop within 0.78m of the best tyre in the dry, then in the wet only added 5cm to that stopping distance. In fact, its wet stopping distance would be a good dry result, which is something you could not say about any other tyre except, perhaps, the Lassa in second place. Meanwhile, the Yokohama’s third place in the wet braking took its tally to an impressive four silvers and two bronzes across the disciplines, which could equally be an overall results spoiler…
OF THE more pragmatic tests we’d ideally subject our Touring-spec tyres to – to complement the safetyfocused dynamic disciplines – tyre noise is the one that’s feasible within a two-day test timeframe. Others would include tyre wear and rolling resistance (and its effect on fuel consumption), which would also require a larger test budget, and not just for the extra weeks’ worth of works burgers for the team. Measuring sound pressure level in decibels is quick and easy by comparison. We triggered the ‘peak-hold’ function on the SPL meter before setting a 60km/h cruise on a nice, gnarly piece of coarse-chip road to log a peak dB figure. More aggressive tread patterns generally make more noise, which is the trade-off for their greater grip, though tyre compound and construction come into it, so that’s not always the case. It’s certainly possible to have a quiet, grippy tyre, or a noisy, slippy one. The decibel scale is a non-linear logarithmic scale in which, for example, a 60dB noise is 10 times more powerful than a 50dB noise. To express some real-world scenarios in the dB scale, 60dB is the volume of normal conversation, city traffic clocks around 90dB, and a concert rocks at up to 115dB. Oh, and a 63.5dB tyre is noticeably noisier than a 57.5dB one – the spread of our test field.
THE noise test certainly shook up the order, with the Momo and Roadstone tyres recording their best results (third and fifth respectively). Of the test tyres, the Dunlop Sport Maxx RT was the quietest, at 59.0dB, but it was a bit noisier than the Hankook control tyre (57.5dB), which technically took the top spot. The field was spread across 6dB, which might not seem like much, but because of the way the decibel scale works, that’s quite a difference in cabin noise levels.
In terms of correlations between tyre noise and performance, the Continental and Michelin are notably better at gripping than gliding quietly over a rough road surface. Conversely, the Hankook control tyre and the Momo bring hushed highway cruising ahead of athleticism.
MANY drivers don’t check their tyre pressures often enough, which is a fundamental safety oversight when you consider that those four rubber patches are your only connection with the road.
After several weeks unchecked, a tyre might have lost 25 percent or more of its placard pressure, which is 8psi in the case of our i30 test car. We duly deflated its tyres from the recommended 32psi to 24psi before hitting the skidpan. The pressure drop resulted in a slalom time that was one-tenth slower (for dead last), a two percent reduction in average g in the cornering test, and a braking distance increase of 0.16 metres – all small but significant costs for laziness.
FITTING larger-diameter wheels with lower-profile tyres is a proven way to improve the looks of your car, but what about the performance? We wanted to get to the bottom of whether big wheels and small sidewalls actually improve handling and outright grip, or just make the car feel sharper. The 225/45R17s fitted to the i30 were OEM tyres (on factory wheels) that come standard on higher-spec versions of the car. Renato described the tyres as direct and consistent with hard sidewalls and did the slalom in times that, on average, would slot the 17in touring tyre into second place. Meanwhile, the roughly 10 percent increase in tyre contact patch brought two percent more lateral grip.
A CAR might wear overinflated tyres for a couple of reasons. Perhaps an inexperienced tyre fitter ignored the manufacturer’s recommendations, or maybe an enthusiast (or cunning car company PR rep) pumped them up in an effort to gain a free handling upgrade. We upped the i30’s pressures by 25 percent to 40psi before tackling the tests. Sure enough, the control tyres gained three percent in lateral grip and took 39cm less to stop, but the biggest gain came in the slalom, where the highpressure control tyre would have finished second rather than eighth. Why, then, doesn’t Hyundai recommend 40psi? The i30’s placard pressure considers comfort as well as performance; we didn’t quantify ride compliance, but an extra 8psi brings a noticeable increase in harshness.
PRODUCTION car racers have been known to use buffed-down road tyres to reduce tread block squirm, and we know slicks stick in the dry, so worn tyres could perform well in these conditions, too. In the wet, however, it’s highly advisable – as well as a roadworthiness requirement – to have a certain amount of tread. We tested a set of wellscubbed (with a legal 2mm tread depth) tyres in both dry and wet conditions. In the dry, the i30 shod with worn tyres bolted through the slalom in record time – quicker than every other tyre at 3.06sec – and posted a cornering g figure that was among the best of the brand-new tyres. But it lost its grip in the wet, recording the slowest average slalom time of all bar the underinflated control tyre, and a lateral g figure seven percent adrift of the wet cornering test champ. But the worst was yet to come. The worn tyres took 8.7 metres – more than two i30-lengths – farther to stop than the average tyre, or 11.3 metres (or 43 percent) farther than the best tyre tested. Worn tyres are great in the dry, then, but they’re woeful on a road car that has to deal with rainy days.
FOUR first places from eight disciplines for the Continental ContiPremiumContact5 would seem to make it the overall champ, right?
Wrong. The Dunlop, Michelin and Toyo tyres secured a first place each, and the Toyo also scored a second on the skid circuit. Meanwhile, the Michelin snagged a second, a third and a fourth, and the Dunlop finished in sixth or above in every discipline. One of them must be the victor, surely? Wrong again. That’s because there was a dark (black, in fact) horse among the field.
The Yokohama Advan Sport V105 didn’t win any discipline outright, but it was right at the pointy end at almost every one of them, securing four silvers, just for starters. Then there were the two thirds and a fourth; its worst result was sixth – equal sixth, as it turns out – in the noise test, which counts for little if you’re focused on safety and handling. The Yokohama was the class of the field, and put in its best showings in the dry cornering and braking, and the slalom in both wet and dry conditions. Interestingly, if you consider only the results of the dry tests, the Yokohama would still win, though if you took only the wet test results it would be pipped by the Continental, which took the silver overall. Conversely, the Continental falls to third if you consider only dry test results. Like the Continental and the Yokohama, the Dunlop (third overall) offers a great mix of dry and wet weather performance. It drops to fourth if you look at only the dry test results. One last look at the dry-only and wet-only results reveals that the Michelin lost out because of its leaning towards dry performance. Second across the dry tests, it slipped to eighth in the wet; it finished fifth overall. Shockers? Well, even the lastplaced Momo M3 performed far better than the set of worn, yet legal tyres tested, which were diabolical in the wet. The message: Make sure your tyres have plenty of tread and, if you can, buy a good brand such as those standing tall on the Wheels Tyre Test 2015 podium.