Preview: Michelin Premier A/S
Well-worn but still performs. New mix and tread design helps maintain performance throughout life of the tire.
LAURENS, SOUTH CAROLINA?Round two of my tire-testing journey took place at Michelin?s Laurens Proving Grounds, about an hour southeast of Greenville, S.C.
This test was designed to show off the new Michelin Premier A/S tire.
Michelin claims its new EverGrip technology is as groundbreaking as its 1992 brainwave to add silica (sand) to the rubber compound to improve stability and traction.
Essentially, EverGrip has two components.
First, a new compound that consists of silica, a polymer that spreads the silica more evenly throughout the tire, and sunflower oil, which helps keep the rubber pliable in colder weather.
The second component is tread design, which is focused on retaining performance characteristics throughout the life of the tire. Two main design details are in play here.
First, the cross-section of the main grooves is trapezoidal, rather than V-shaped.
The longer horizontal elements of the trapezoids are closer to the centre of the tire, so the grooves actually get larger as the tread wears, rather than smaller, as they do with V-shaped grooves.
A key metric for wet-weather tire performance is the so-called ?void? ratio, which measures how much rubber there is compared to how much empty space.
A typical new all-season tire is about 70/30, but devolves to around 85/15 when half-worn as those grooves get narrower.
The Premier starts at 70/30, but essentially stays there throughout the life of the tire.
Also, extra sipes (tiny slits in the tread that create biting edges and help disperse water) are buried in the tread, only to emerge as the tire wears, effectively growing new tread as it ages.
Michelin goes so far as to claim that the Premier is not only better than the competition when new, but that half-worn Premiers are better than new competitors.
Can they prove it? They can surely try.
In otherwise identical Cadillac CTS sedans equipped with new Premiers, half-worn Premiers, and two competitive brands, we negotiated a tricky slalom course that was completely and continuously soaked by a sprinkler system.
We didn?t have timed laps, so there are no hard-and-fast metrics here. Hence, I don?t feel it?s fair to identify the other brands. But you would recognize them.
Anecdotally, with the new Premiers, it didn?t feel like there was any water on the track at all. The car turned in when I turned the wheel, it stopped when I hit the brakes ? all as it should.
The seat of my pants isn?t well enough calibrated that I could tell a huge difference between the other two brands. But for sure, they were nowhere near as stable as the new Premiers, and washed out easily in several corners.
And true to the company?s claims, the half-worn Premiers were at least the equal of the other two new brands, with maybe a touch more hydroplaning compared to the new Premiers on the most deeply flooded stretch of the track.
To measure wet braking, we used a special skid lane with a low coefficient of friction.
Leaving the ABS on, we?d run the Caddies up to 100 km/h, then bury the brake pedal.
On-board recording equipment measured the stopping distance from 100 km/h to 0, so hitting the brake pedal at exactly the same point on the track wasn?t critical.
Two runs per brand. With proper metrics, no anonymity anymore.
My numbers for the Michelins, buffed down to 5/32 inches of tread depth (i.e. well-worn): 102 and 100.8 feet.
For new Bridgestone Turanza Serenity Plus: 112.9 and 109.2. And for new Goodyear Assurance Tripletred A/S: 110.5 and 109.1.
So, roughly a 10-foot difference, or about 3 metres ? darn-near a short car length. The other journalists got similar results.
OK, this is a limited sample size, and it was not a double-blind study. But you?d have to say the numbers we got support Michelin?s thesis.
Transportation for freelance writer Jim Kenzie was provided by the manufacturer. Email: email@example.com.