May 19th, 2011

Second opinion: Michelin Pilot Super Sport

When it comes to the concept of learning, there is little more useful than a directly proportional relationship. Whether it is a pay as you go mobile phone or the principle of momentum, we are good at understanding when one factor directly increases or decreases another.

As far as the four sections of rubber keeping a car in contact with the road go, our general consensus is often that there is one basic and proportional rule in place: The softer the rubber, the more grip available, but the shorter the lifespan.

With the launch of their Pilot Super Sport, Michelin have really confused what was once a simple relationship, managing to increase countless capabilities of the premium product without a decrease in any related characteristic.

Last week, I made my way down to Porsche’s Experience Centre at Silverstone to see how this French manufacturer has managed to bend such parameters. The allure of the technology would have been enough, however since there was the option to test the new product in a smattering of interesting metal; well, I wasn’t going to say no to that either.

As we well know, motorsport is a punishing proving ground, and nowhere is the development more crucial and paramount than in endurance racing.
Michelin have applied understanding from 13 consecutive victories at Le Mans to their new product for super sports cars and ultra high performance tuning. On the face of it, any type of car with a tax disc may appear to be a whole different arena, however when you are looking for maximum all-round performance with the longest life possible, the two are more closely linked than you might think.

Their new Pilot Super Sport has been developed from the previous Pilot Sport 2 to an extent where wet and dry road-holding have been increased (1.5 seconds over a 2700-metre test lap), wet and dry braking distances have been seriously reduced, yet tests show an increase of 10% greater mileage capability on the road and a staggering 50% more laps being possible on the track.
Luckily, they remembered that humans are sceptical beasts (especially when it comes to parting with hard earned cash) and so conveniently lined up a selection of tests to highlight said results in front of our very eyes.

During the tests at Porsche’s stunning facilities, there was the ability to compare the PSS tyre back-to-back with its competitors, and being truly sportsmanlike this was by no means against re-moulded Chingchangs, but top premium brand products that even Michelin themselves denote to be good performers.

As the starting point, a cornering test on a simulated wet roundabout demonstrated eye-opening results, in both the ability of the PSS tyre to corner at an increased speed over its contemporaries, yet more-so in the ability to notch down the diameter of the circle at a constant speed. Gentle inputs allowed the test car (an Audi TT) to just keep on nibbling its way inboard, with a gentle lift allowing even more in the way of line tightening and extreme tucking in. I’ll leave you to make you own Simon Cowell-based pun there. The same playful inputs in the comparison car gave rise to a noticeably unsettled combination of under and oversteer as well as slithering off the desired line.

As reassuring as it is to know about the ultimate grip levels on offer during cornering, it is important to remember that steering feel and progressive confidence are perhaps more important attributes in a performance tyre for many road-going buyers.

Porsche’s handling circuit is basically the perfect B-road, except crossed with the driving nirvana that is a guaranteed lack of any oncoming traffic. With this environment a given, we carried out dry laps where a pair of 997s (C2S) were driven as one might on a spirited cross-country blast. At this six-tenths action, the first 997 reacted with utter precision and remained thoroughly composed, even when given deliberate excess throttle through the tighter corners and off-camber undulations.

Jumping straight from this Michelin-shod car to another equipped with a competitor’s tyre gave the opportunity to carry on using the exact same pace and lines, such that would not trouble the 911’s thoroughly developed chassis.
Shod with what is still mighty fine rubber, identical cornering speeds clearly didn’t send us flying into a grassy Silverstone knoll, but the subtle differences were quite evident. The odd chirrup and squirm here, a subtle developing hint of understeer there, there was no problematic lack of grip or traction, but it was apparent to see where the ‘lesser’ tyre might start to slow or upset the pace if it was a battle against the clock. This second vehicle was still plentifully capable, yet it simply didn’t feel as entirely untroubled and instill as much confidence as the earlier car, both in terms of ability and (subjective) steering feel.

As far as the technology itself is concerned, the PSS integrates three main areas of development (well, three that they are prepared to reveal to all and sundry).
The first is the use of dual compound technology across the width of the tyre. Here, the majority of the tread’s width uses a different, wet-biased compound to the outer edge; a band of carbon black-reinforced elastomeric rubber that is directly related to the Le Mans winning mix. The spread of compounds and co-efficients of friction allow the different areas to stick to their respective tasks in hand, as well as preventing straight line driving from undue wear of the sticky cornering rubber.

You might have thought that the yellow fibres under the surface were a tread depth indicator for some van drivers, but they actually have a primary role in forming and holding the carcass together. Michelin however sensed there was room for a much more active role in their job description, and the new ‘Twaronâ’ belt features a unique weave that exerts variable tension on the surrounding rubber. This grips the centre of the tread more tightly than the shoulders, and the result is a more even distribution of forces and uniform flat contact patch as the wheel speed increases; preventing the natural ballooning towards a motorcycle tyre-esque cross section.

While we’re on the subject of the contact patch, this has been cleverly optimised so that during cornering the shape of the patch changes, yet the actual surface area of rubber in contact with the tarmac stays just the same. This allows for a better distribution of forces and temperatures, and ultimately more uniform, optimum grip and traction.

Finally, as much as I could labour on about the technology and my subjective experiences, what you really need is parting shot; something to take home in a proverbial internet party bag with a slice of food-for-thought cake. Even with the other abilities, feel and lifespan, a wet (or in our case, damp) braking test gave such a conclusion.

We used a pair of identical BMW (E92ƒ) 325i M-Sports equipped with dataloggers to investigate wet braking in a test that required little input from us drivers (and hence lacked erroneous results). The automatic cars were hoofed up to a cruise-controlled speed of just under 50mph, then we simply hit the (ABS) pedal to the left with equally maximum force and held on.
After three days of subjecting the cars to the same tests from countless eager pilots in the driving seat (people, not tyres obviously), there was a consistent average difference between the two cars’ results. At the time of my visit, the difference in this braking distance was hovering at around two metres.

That’s pretty much the same length as a Mk1 Smart Fortwo – have a think about that the next time you’re in a 50mph motorway limit and it seems like you could step out and walk alongside.

Words: James Winstanley