Originally Posted by Bob Barnes
Better yet...let's take a look at what bevels do. It's not as mysterious as many would like us to believe!Base Edge Bevel
--primarily controls "predictability" and how far a ski must be tipped before the edge engages
Side Edge Bevel
- Optimal bevel: Flat (unedged) ski is predictable, not "grabby"; skis are easily steered through the transition; edges engage smoothly but positively when appropriately tipped, and can still be "feathered" into a skid when needed.
- More bevel: Ski must be tipped further before the edge engages, allowing you to incline further into the turn before it hooks up and starts carving. Some strong skiers prefer this, especially those who prefer to stand fully on their skis with minimal "unweighting" through the transition, as they roll the skis from edge to edge. (This is rare, but I know a very strong racer who, for a while, tuned his slalom skis with a 3 degree base edge bevel, requiring him to move way inside the turn before the skis, which were then on a huge edge angle, started carving a very tight radius turn. The downside is later edge engagement; upside is incredibly tight carving radius when the edges finally do engage.)
- Too much bevel: flat skis are "swimmy" and do not feel like they'll hold very well, because you have to tip them a long way to get them to grip.
- Less bevel: Ski edge engages quickly when minimally tipped: ski is less forgiving, and requires very accurate, precise, and consistent movements.
- Too little bevel: Ski is "grabby" and unforgiving, difficult to steer smoothly, and very uncomfortable when flat on the snow, and "catching an edge" is more likely when skidding or sideslipping.
- Too little bevel: ski wants to hook up too quickly, trying to carve before you are sufficiently inside the turn for balance; the sensation is that the ski keeps coming back underneath you as you try to roll it onto edge to carve. Strong skiers with sophisticated pressure management skills may prefer this, as they can unweight the skis sufficiently to keep them from starting to carve until they are ready, then subtly re-establish pressure when the time is right. (In a full pendulum swing, the same racer described above now tunes his slalom skis with zero base edge bevel. He can now carve earlier in the turn, but must be extremely accurate in his movements as his skis hook up so suddenly and vigorously.)
--primarily controls edge grip; more bevel grips better
- Optimal bevel: skis hold well on hard snow, but not so aggressively that they cannot be steered or feathered into a skid when needed.
- More bevel: skis hold better on harder snow, may bite too aggressively on softer snow.
- More bevel: edge forms a more acute angle (less than 90 degrees); this makes it feel sharper, but it also makes it more fragile and dull more quickly. It's sharper, but you'll need to maintain and resharpen it more frequently to keep that edge.
- Less bevel: skis are easier to steer and skid, but do not hold well on hard snow.
- On very hard snow and ice, some side edge bevel is important for an additional reason; without it, the side of the edge can literally pry the edge of the ski out of its groove as the ski tips further. A graphic would make this concept easier to explain, but imagine driving a shovel into firm snow, and then prying down on the handle. The blade of the shovel pivots against the surface of the snow, prying the tip of the shovel out. Now imagine that the shovel blade is curved lengthwise, so that it leaves a hollow area underneath it when driven straight into the snow. Now you'll have to tip the handle down further before the shovel blade touches the snow surface and begins to pry the edge out. In effect, side edge bevel accomplishes the same thing, allowing the sharp edge to continue to cut into the ice as the ski tips further on edge.
(A few years ago, VailSnoPro and Cgeib put together a short PowerPoint presentation with some great animated graphics to explain these effects of bevel. Perhaps one of them might post some of those images here, if we're really nice!)
Many things affect "optimal" bevel, including ski construction, snow conditions, technical skill, and skier preference. Torsionally softer skis twist more when tipped on edge, effectively increasing base-edge bevel at the tip and tail, and may benefit from slightly less base edge bevel as a result. Softer snow conditions do not require such tenacious edge grip, and may suggest less side edge bevel. Very precise and skilled skiers can handle--and will probably prefer (in most conditions)--an aggressive tune with minimal base edge bevel (0-0.5 degree) and more side edge bevel (3+ degrees); less-skilled skiers would find this tune difficult to manage, and may do better with a less aggressive tune (0.7-1 degree base, 1-2 degree side).
0.7-1 degree base and 2 degree side edge bevel is a pretty standard tune for many skis. Most skiers will find that tune predictable and easy to manage, yet sufficiently grippy for most turns on reasonably firm conditions. (Of course, regardless of the bevels, skis must also be sharp
if they are to hold well.) Many skis come this way, and many shops have their edging equipment set up this way by default. Your mileage may vary, as they say.
Many people seem to think that the manufacturer's tune is somehow a "recommended" tune for that particular ski, but I would not look at it that way. It's usually just a tune that they think most "typical" skiers will find easy to ski. Rather than worrying about "manufacturer's specs" or someone else's recommendations, I encourage you to go by feel, with the understanding of what different bevels do. Skis grabby and unpredictable? Add base bevel. Skis not holding well enough? Are they sharp? If so, add side edge bevel. Skis too grippy? Reduce side edge bevel.
Finally, remember that changing a bevel requires grinding away more metal from the edge. Unless you're a racer with free skis, I recommend finding a tune that you like and sticking with it. For what it's worth, I tune pretty much every ski I have at 0.5/3 (by convention, the base edge bevel is always stated first). I ski them that way in every condition. Sometimes I'm tempted to increase the side edge bevel when it's extremely firm, but I don't often do it.
Once you settle on a tune you like, I recommend getting a set of good bevel guides and a file and diamond stone or two. It doesn't take much to learn to use these basic tools to keep your edges in great condition. Unless you cause some real damage, five minutes a day with a diamond stone will usually be all it takes to maintain your tune, and your skiing will be much happier for it!