What a fresh tune changes on ice

The honest starting point first: the lab does not model a tune. It has no edge sharpness, no bevel and no base condition. What it has is one number for each type of snow, called μ, which says how much sideways force the edge can take before it slips. On ice that number is 0.6. A tune is the thing you would change if you wanted to move it, so this page shows you what moving it does. It does not tell you how far a tune moves it.

Slide the edge angle on ice, on the carver archetype. At 40°, with you angulating the way you would on a good day, your body leans 30° from vertical, and underfoot has about 101% of the grip it needs, which means it only just holds. Drop μ to 0.5, as if the edges were worn, and the same turn has 84% of what it needs and is marginal. Lift μ to 0.7 and you have 118%, with room in hand.

Put it another way. At μ 0.5, the steepest body angle that still holds is about 26° from vertical. At 0.6 it is about 31°, and at 0.7 about 35°. Each 0.1 of μ is worth about four degrees of body lean in this model. Push the edge angle up to 50° and even μ 0.7 is only marginal underfoot, while 0.6 and 0.5 slide.

The tail and tip give up before the middle does. At 40° the tail slides even at μ 0.7, and the tip slides at 0.6. They carry very little load on firm snow, so there is little to hold with, which fits the advice to keep your weight over the middle of the ski on ice.

What to take from it: on ice the model sits close to its limit, so small changes to grip move the result a lot. A tune is one of the things that could change that grip, though the model cannot say by how much. Treat the 0.5 and 0.7 as what-ifs, not measurements.

Everything else matters as well: how much you lean in, how smoothly you change edges, and the width of the ski. If you want to know what your edges need, ask your shop, and tell them what snow you ski.