Rules and regulations are the basis of a functioning society but every once in a while, a new technology comes along and forces a rethink of the rules. The first car was invented in 1886 but up until 1896, British law required every car to be driven behind man waving a red flag/lantern. It was one of the reasons why Germany’s nascent car industry leapfrogged Britain’s, even though the latter first invented self-propelled vehicles - steam engines and trains.
When it comes to tyres, the law states that the minimum allowable tread depth is 1.6 mm but no responsible motoring publication will tell you that’s acceptable. A tyre’s wet braking performance diminishes significantly once the treads wear past the 60 percent mark. Risk of aquaplaning – a condition where your tyre floats above a thin film of water on the road – also increases significantly.
Our advice has always been to preemptively change your tyres by monitoring the tread wear indicator – which is typically marked by a tiny triangle on the sidewall, or in the case of Michelin tyres, where the little Michelin Man symbol is pointing to.
That was until Michelin told us that we were wrong - well, sort of. Since 2014, Michelin has commercialized its EverGrip technology that allows – and we know this is hard to be believe - a badly worn Michelin tyre to brake better in the wet than a new premium brand tyre.
Note the gap in wet braking distance between a set of worn (2 mm tread depth left) Primacy 4 tyres and new tyres by other premium brands.
Yes, it sounds unbelievable but such is the progress of Michelin’s tyre technology. Mind you the new tyres compared against is not some dodgy DingDong brand tyres, but are similarly premium European and Japanese brand tyres, with results verified by Germany’s independent TUV Rheinland.
Just to prove a point that the results are repeatable and consistent, a live demonstration was also done during the Primacy 4’s regional launch in Thailand.
The worn Primacy 4 tyre on the left was used in the demonstration on wet braking.
Michelin says the commonly given advice of precautionary tyre replacement is wasteful. It’s not only bad for the environment but adds financial burden to consumers. The company explains that if all tyres are equipped with EverGrip technology, there will be 128 million less tyres discarded in Europe alone annually.
Of course all tyres will wear out and you certainly can’t use it past the 1.6 mm tread wear limit – because that’s the legal limit. It's something that Michelin is lobbying governments of the world to change but that's another story.
The Michelin Primacy 4 is Michelin’s latest comfort-oriented premium tyre. It’s recommended for D-segment and above sedans – the likes of a Toyota Camry, Honda Accord, or even a Mercedes-Benz C-Class or a BMW 3 Series. However since the tyre is available in 15- to 19-inch sizes, it’s also suitable for cars like a Toyota Corolla Altis or a Honda Civic.
It also well-suited for crossovers like a Honda HR-V, or even large minivans like a Toyota Alphard/Vellfire.
This particular review set is fitted on a third generation Toyota Prius, swapping out the previous Bridgestone Ecopia EP200 tyres. As this is not a fuel-saving tyre like the Ecopia, the Primacy 4’s sidewalls are softer and the improvement in ride quality is immediately obvious.
As expected, the trade-off is slightly higher fuel consumption. Tyre sidewall flex is one of the ways a tyre’s kinetic energy is lost and with softer sidewalls, the Primacy 4 has a 7 percent poorer mileage compared to the Ecopia EP200, based on yours truly’s driving habits and travel routes. Keep in mind that a closer alternative for the Primacy from Bridgestone is actually the comfort-oriented Turanza.
The slight increase in fuel consumption is an acceptable compromise because with EverGrip, drivers don’t have to replace it as early as they are normally advised to, thus equalizing any additional expenses in fuel over a fuel-saving tyres.
Where the Primacy 4 trumps best is the substantially more comfortable ride that it offers. The cabin is now so much quieter and ride is a lot more pliant. It’s amazing how much more comfortable a car can become simply by switching to a set of premium tyres.
Driving on wet conditions, road holding is exceptionally good but to be honest, the same can be said with many new tyres from reputable brands. What separates the Primacy 4 from its competitors is Michelin’s promise that the tyre will maintain the same level of performance throughout its service life.
Pushed hard into a corner, the Primacy’s soft sidewalls will flex, reminding you that this is not a Pilot Sports but for all intents and purposes of a daily car, the tyre ticks all the right boxes.
The secret to how Michelin’s EverGrip is able to extend the safe-use limit of the Primacy 4 is by redesigning the tread pattern to have a wider, U-shaped groove, which Michelin says increases water dispersion by a whopping 50 percent. In other words, the grooves are designed expand in width as the tyre wears down to make up for the diffferences in tread depth.
While other tyres will see a degradation in performance as the smaller grooves on the sides called sipes wear away, the Primacy 4’s sipes actually expand as the tyre’s surface wear down, further aiding water dissipation.
Clever manipulation of materials also allows the tyre to better absorb and disperse energy more evenly, because the physics of braking is essentially about how fast a tyre can convert kinetic (moving) energy into something else, usually heat. The more evenly a tyre dissipates the energy, the better it can maximize grip.
But let’s not get distracted with its wet braking performance, because a Michelin tyre wearing the Primacy name needs to, above all else, offer a comfortable ride.
Data supplied by Michelin claims the Primacy 4 is 0.3 dB quieter (while at the same time offering 4 percent better grip) than the previous Primacy 3, which was already among the quietest in its class.
Much of a tyre’s noise is created when the tread blocks expand and contract as the tyre rolls along. The change in air pressure within these air pockets act like a series of miniature air pumps creating noise. The Primacy 4 benefits from the second generation of Michelin’s Silent Rib design, which uses inter-locking bands to minimize tread block deformation.
Every tyre has its pros and cons. The science behind tyre design is all about balancing the individual properties of each material used. There are many one-hit wonder tyres on the market - tyres that are good at doing just the one thing they are advertised, but performs below average elsewhere.
What separates Michelin tyres from others are the all-rounded performance across all measurable metrics. It's a promise given by all Michelin tyres that wear the Michelin Total Performance logo.
Downsides to the Primacy 4? It’s hard to find any because as mentioned, it’s a very well balanced all-rounder. Performance at the upper limits of driving could have been better but if that's your requirement, you should be looking towards the Pilot Sport series.
If we have to highlight any negatives, it will be our lingering doubts with Michelin’s claim of sustained wet braking performance even when worn. Yes, we have seen the data but our torrential rain here can be very extreme. Perhaps it’s best to err on the side of caution and replace the tyres once it wears down to 2 mm rather than the minimum allowed 1.6 mm.
Recommended retail prices ranges from RM344 for 15-inch sizes to RM1,042 for 19-inch sizes.