I switched my P85D from the Stock Michelin Primacy 19's to Nokian Hakka R2's today. The temps were in the mid 20's and I had a nice packed powder base on my driveway, so it was time for a test to compare the two. As you can see in the picture below, I had a nice run out to the cottonwood tree, doing 0 to 20 to 20 tests in the snow by using max acceleration until I saw 20 then hitting the brakes to come to a stop again.
The temps were at about 24˚F for the Michelin runs and warmed up to about 27˚F for the Hakka runs. Also, the Michelins were at outdoor temps when I did the runs, and the Hakkas were at garage temp of about 48˚ at the start. Both of these temperature differences would disadvantage the Hakkas. I use the "Motion Data Logger" app from JadeMind on the iPhone to log the accelerometer data at 100 Hz and then post processed it in a spreadsheet. I averaged and subtracted out the gravity vector and then calculated the magnitude of the remainder acceleration vector. This makes both acceleration and braking (deceleration) positive. If you look closely, you can see dips in the acceleration plots where I moved my foot from the accelerator to the brake pedal. All tests were done with full on accelerator and brake pedal, letting traction control and anti-lock braking do their thing. Each run had some small steering drift that I easily corrected.
The Hakkas came on strong with about 0.4g acceleration and held that, doing a little better than 0.4g braking. The Michelins started at about 0.2g and after about 2 seconds rose to a little over 0.3g acceleration, but did worse in braking at less than 0.3g. After looking at these data a few ways, I would say that the Hakkas have about 40% better average grip, with even better than that in initial acceleration and hard braking. Rough 0-20-0 times were 9.6 seconds for the Michelins and 6.8 seconds for that Hakkas. The corresponds to stopping distances that are reduced by more than 30%.
Packed powder is probably best case for the Michelins in this Michelin Primacy vs Nokian Hakka R2 comparison. This fresh, cold, grippy snow gives pretty good traction. I am sure that in icy conditions the Hakkas would have won by a bigger percentage. See
Nokian Cryo Crystal Concept — Nokian Tires for a description of the Nokian Cryo Crystals in the Hakka R2.
Given that I have a stretch of 15-16% grade up my driveway in Pagosa, I am very happy to have the Hakka R2's for Pagosa. Subtracting 0.16g to overcome the 16% grade from the above numbers, gives me a net acceleration of 0.04-0.14g with the Michelins vs 0.24g with the Hakkas. That is a big difference for starting uphill and stopping downhill!
