What is Ski Flex?

by Simon Knott | Posted On: March 28th, 2022
girl skiing

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Sometimes when you’re browsing in the ski shop, you’ll come across a customer who tries out different skis by standing them upright and bending them to see how flexible they are. Then, you’ll see him grabbing the top of a ski across the width with one hand and lower down with the other hand and then twists the ski, to try out the twisting resistance. But why is he doing this? What difference does the flexibility of skiing make?

The flexibility along its length and the twisting flexibility across its width are both characteristics of ski flex. Different degrees of ski flex is achieved by altering the construction of the laminated wooden core layers in the ski. Beginners and freestyle skiers benefit from softer ski flexibility, which is more forgiving, while expert skiers and racers benefit from a harder ski flex, which gives better edge hold and control.

Skis are manufactured differently to achieve different flexibility or stiffness in construction. This difference in flexibility directly affects the performance of the ski on the snow. Often there is a trade-off between characteristics, which skiers can use to their advantage.

If the skis are manufactured to be particularly flexible, then the tip and tail will respond to the contours of the snow and bounce off the surface, releasing the edges along that section. At the other extreme, a more inflexible ski will tend to just slice through surface snow, as there isn’t enough flexibility to ride over the surface.

For a beginner, a more flexible ski is much more forgiving and easier to control, while a more expert skier will be looking for a stiffer ski, which gives him sure edge control, stability at speed, and good responsiveness.

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The expert skier will also have the skills to overcome the less forgiving nature of stiff skis. Therefore, when choosing skis, it is vital to match the ski flex to your skiing ability

How Do Different Flex Skis Perform?

Skiing dowhill

The mechanics of how a ski travels over a snow surface varies with the stiffness of the ski. Typically, the surface of the snow is constantly changing with the difference of the gradient of the slope and the random, uneven snow surface that has been kicked up.

In riding over it, the tip and tail of a more flexible ski will bounce over the surface, releasing the immediate edge as it does so. This can become so extreme sometimes it almost feels as if the skis are beating, as they repeatedly connect and disconnect with the snow.

With a stiff ski, however, the distribution of the skier’s weight forces the ski edge to keep good contact with the surface along its entire length, giving a good level of control. Racing skis are a good example of skis with stiff flexibility. They are designed specifically for fast speeds while maintaining strong edge contact and responsiveness.

At the other extreme, freestyle skis often have high flexibility. The freestyle skier makes use of this flexibility in jumps, awkward landings, and during tricks,

How Is Flexibility Built Into the Construction of a Ski?

Skiing with Friends

As a part of ski manufacture, the central wooden core is fabricated from laminated strips of hardwood. To achieve a base level of length flexibility these laminated strips run continuously along the whole length of the ski.

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After years of research, manufacturers have learned to laminate different types of wood into set patterns, which enables the ski to achieve its required characteristics. Sometimes the construction of the core is aided by the addition of extra materials such as carbon fiber, titanium, and foam.

The lamination of the different layers in the ski is the key to its torsional rigidity or its ability to twist across its width. The construction of the wood core is fundamental to the strength and flexibility of the finished ski.

The Flex Pattern of the Ski

The flex pattern of a ski always refers to the tip and tail only and is measured to include the length flexibility, as well as the torsional or twisting flexibility. The flex pattern varies according to the ability and the weight of the skier.

Additionally, the flexibility of the ski changes along its length. It is manufactured to be more flexible at the tip and tail, while much stiffer in the cutaway where most of the downforce is concentrated.

* Longitudinal Flex

The longitudinal flex of a ski is the flexibility of the ski along its length from tip to tail. The core, length, and the structural laminated layers all play a part in the specification of longitudinal flex.

* Torsional Flex

The torsional flex or twisting relates to how easy it is to twist the ski from edge to edge. A more flexible torsional flex helps the ski to perform better in tighter turns, while a stiffer torsional flex offers better performance in carving.

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When you make a carved turn the entire length of the edge of the ski is in contact with the snow. Your full body weight is transferred down through your boots into the skis, where the cutaway section of the ski flexes to create the turn radius or arc of the turn.

However, even though the whole ski edge is in contact with the snow there are different amounts of force pressing down across different sections of the ski. For example, the force exerted at the tip of the ski is different from that exerted at the waist and at the tail. This creates a torsional or twisting force.

A ski that has been manufactured with strong torsional flexibility will stand up to these different forces much better than a softer ski with less torsional strength.

skiing red jacket
Photo by Robert Tadlock licensed under CC BY 2.0

What Ski Flex Is Best For Me?

As with so much equipment in skiing, the ideal stiffness of your skis will be a matter of compromise. So, it’s always best to talk over your requirements with someone who has a good understanding. Numerous factors come into play including your height, weight, ability, skiing frequency, and preferred terrain.

Often an adaptable ski can optimize the benefits of better flexibility in the tip and tail, while a stiffer underfoot section maximizes power transfer down through the boot.

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