Originally Posted by
MinnMan
The different symbols are for different types of ice - one from a bobsled run, the other from a hockey rink. But I don't know which is which. Either way, chalk up the difference to different textural properties of the ice - different sized ice crystals, different alignment of the crystals, etc. - or possibly different impurities.
Thanks for the graphic. It doesn't say which hardness measuring system is represented (Mohs, Vickers, Brinell, etc.), but it's apparent that hardness is inversely proportional to surface temperature.
It would be interesting to see the relationship between the hardness of ice and its shear strength. The studs, whether made of steel or tungsten carbide, must be harder than the ice, so there shouldn't be issues with penetration. If the studs are worn and rounded, as Hypno Toad suggests, the studs would more easily slip up and out of whatever purchase they had. Studs with a good engagement with the ice could still slip by physically shearing the ice.
So, not being a mechanical engineer or having any particular expertise in the physical properties of ice, I set out to see how my studded tires perform. We've had sustained temperatures in the upper teens and lower twenties for a week or so, and the ice seems hard and adequately thick. Skaters and ice fishers were in evidence. Images below.
What I *can* say is that the tires (Nokian "Extreme 294") have plenty of traction. It is possible to spin the rear wheel in a lower gear, and modest brake pressure on either wheel would cause a skid. So extremes of acceleration and braking are to be avoided, but there is plenty of usable traction in between.
BTW, the Nokian studs are tungsten carbide, and each stud has a sharp point on it. This is different than the studs on my Schwalbe tires, which are also carbide, but are cylindrical with flat ends. Carbide wears very slowly, even on pavement. Some less-expensive tires have steel studs which wear much faster.
Hard, clear ice!
It's nice not to fall!