What should I know about ski flexes?
All skis are manufactured with a specific flex or bend. With touring and classic skis, this flex determines how long the kick zone of the ski is, and how much weight is required to push the kick zone into the snow. If the flex is too soft, the skis will drag on the snow. If the flex is too hard, it will be difficult for the skier to push down the kick zone of the ski to get the needed kick. Most of the Atomic, Fischer and Madshus racing skis come in soft, medium, and stiff flexes for classic. For skating skis, soft is not an option - the skis will come medium, hard, or in some cases soft/med and medium/hard. There is always going to be some overlap and subjectivity when selecting the proper ski length for a person's weight and height. Their skiing skill level should be considered too. But weight is by far the most critical factor for touring, classic racing, and backcountry skiing because of the ski's grip zone or central "camber" or flex. A softer flex works best for lighter folks and a stiffer or harder flex for heavier folks. Weight of the skier is just as important when selecting the correct skate ski. A medium flexed skate ski is usually designed for softer snow conditions or skiers with a low weight-to-height ratio (i.e., a man 6'2" but only 142 lbs). A medium flex may also work best for someone with less refined technique because the ski will be more forgiving.
Using the example above and "going by the book", the correct length and flex for a Visu Magnum Race skate would be: medium flex, 193cm. However, I might recommend a hard flex 193cm if he is a strong skier or claims to have great ski technique. This is where the subjectivity factor comes into play with ski selection. So, use the size charts
as a guide, and then fine tune to skiing ability and snow conditions. Racing skis are going to have the most overlap and broadest weight ranges; more so than the touring and backcountry skis. This is because of the individual preferences found among racers and the skis. Keep in mind that a certain pair of classic skis that work as an excellent "klister" ski (because of their stiff camber) for a 125 lb. female racer might have the perfect flex to be a "hard" or cold wax pair for a 140 pound skier. With classic, and cold-dry fresh snow, choose a ski at the softer end of the spectrum for hard wax conditions. For old wet snow or hard packed frozen granular, choose a stiffer or harder flex ski. For a ski to perform best for both, select a medium flex model. Most higher end skate skis will come in medium or stiff (hard) flexes and again, a medium flex ski will usually perform better in cold, loosely packed snow while a hard flex is preferred in most normal, harder snow conditions including frozen granular. Most racers prefer a hard flex for skating, except for young skiers - junior high school for example, and skiers with low weight to height ratios (as explained in the previous example). Also, a medium flex may be better for beginners because it is easier for them to press the ski onto the snow in the glide phase, i.e., be somewhat more forgiving.