Straight skis have a uniform width from tail to tip. Parabolic skis feature a deeper sidecut, where the tip and tail are wider than the middle. The shaping difference between parabolic vs. straight skis will affect the rider’s speed, stability, and turning.
Skiing technology has come a long way in recent decades, perfecting the ride to make the sport more enjoyable and easier on the body.
But progress hasn’t gone up — it’s gone out, taking off in several directions depending on the type of terrain you ride. As a result, the best ski types for one slope could be the worst for another.
To get the best ride, you need to understand how design factors into it, and one of the essential elements you need to consider is sidecut, the difference in parabolic vs. straight skis.
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What Is the Sidecut of a Ski?
The sidecut is the curve on either side of a ski that runs from tip to tip. From a bird’s eye view, it gives a ski an hourglass form.
In ski specs, you can get an idea of a sidecut by comparing the width of the tip, tail, and waist, the center of the ski. You may also see sidecut measured in terms of the turning radius, or sidecut radius.
What Is the Sidecut Radius?
To understand the sidecut radius of a ski, imagine the curve of the sidecut continues until it completes a full circle. The radius of that circle is the sidecut radius.
The sidecut radius influences the ease and tightness of handling turns. A smaller turning radius under 17m is ideal for handling tight, hard turns, while a larger radius is best for broader, softer turning.
Because sidecut radius will change with longer skis, you must compare sidecuts between skis of equal length. For example, two different sizes of the same ski will have different sidecut radii yet deliver the same level of turning ease.
The sidecut of a ski affects how it rides in several ways. But its effect will change based on other variables around the ski, including:
- Length and width
- Camber and rocker
These components, along with the sidecut, have a dynamic interplay with each other. In different combinations, they work together to affect performance aspects like skiing speed, turning, and float, the ability of skis to stay on the surface of the snow.
Over the years, experimentation has brought about various designs for specific settings, such as downhill racing, backcountry, and slalom. That has resulted in a spectrum of straight and parabolic ski shapes that we have today.
What Are Straight Skis?
Straight skis are the original style of alpine skis that go back centuries. Viewed from the top, they would have parallel sides. But although there was no clear line between straight skis and parabolic skis until recently, this 100% straight form hasn’t been part of alpine skiing for over 200 years.
The sidecut, though subtle, was added around the early 1800s. It became popular in the mid-1800s when Nordic skiers headed by Sondre Norheim began using undersized waists.
Original straight skis would have a massive sidecut radius, often over 60m. Throughout the 1900s, innovators have experimented with deeper sidecuts for various settings.
A true straight ski won’t be seen in powder bowls or on groomed trails, but it’s still the preferred shape for cross-country and ski jump skis. Although the design has mostly been phased out, those two uses speak to the practical side of straight skis.
Benefits of Using Straight Skis
The choice between parabolic vs. straight skis is a little misleading because nearly all alpine skis sold today are parabolic to some extent. Still, there are benefits to buying a ski with a wider turning radius for some situations.
The waist of a ski has a minimum limit to support a boot and binding, so the smaller the sidecut radius, the bigger the tip and tail. The added surface area creates more drag. At a similar length, a parabolic ski will go slower than a straight ski.
The straighter the ski, the easier it is to run flat. Parabolic skis are more stable while on an edge, and downhill straightaways and long arcing turns are easier to handle at higher speeds with a straight ski.
Downhill racers use skis with a larger turning radius of 30m or more to maintain stability, as do ski jumpers who only need to worry about gaining speed on a straight course. You’ll also see a straighter design for mogul skiers to handle bumps with more control.
Heavy powder common in off-piste skiing demands a ski with greater float to keep from sinking in, and a straighter ski provides surface area without making the skis overly wide.
Powder skis range around 100-115mm at the waist, but many super-fats go much wider. To sustain a short sidecut radius, the tips would have to be extra-wide and subsequently require a wider stance.
Today’s skis range on average between 15-20m in sidecut radius, and powder skis usually fall on the higher end of the spectrum with some running 22m or more. Some ski styles, however, venture into reverse sidecut territory, where the tip and tail are narrower than the waist. These waterski-inspired models are maneuverable in deep powder but are unusable on packed snow.
Modern powder skis are still much more responsive than the original 60m skis, but they’re still relatively straight. Still, the sidecut is only one consideration for powder skiing, as longer skis also provide the necessary float, allowing for more agile ski shapes.
What Are Parabolic Skis?
The parabolic ski as we know it today didn’t emerge until the 1990s. The Elan SCX was a revolution in sidecut design, a GS ski with a super-small turning radius of 15m. On the race circuit, the SCX almost guaranteed a win with its sustained speed.
It may be the ski that brought the sport into the modern era, but enhanced sidecuts were being perfected well before the SCX. Many American brands were also experimenting in more parabolic designs, but they still made them with racing in mind.
The success of the SCX was the turning point for alpine skis, as every manufacturer turned their focus to developing a better parabolic ski. It wasn’t long before skis became shorter to offset the added weight of a wider tail and tip.
Benefits of Using Parabolic Skis
The typical parabolic ski, now commonly called a “shaped” ski, fits the 75-95mm waist width that’s perfect for riding groomed trails. With a more pronounced sidecut, skiing becomes easier to adopt for a larger group of people.
The main benefit to the sidecut has always been the turning ability, and the smaller the sidecut radius, the tighter it can turn with relative ease.
Turning on straight skis while maintaining speed was an expert skill. Riding was concentrated on form, with straight skis requiring a sequence of shifting your weight and adjusting your knee positions to turn without skidding out. Many casual skiers had to resort to wedge turns or the more advanced stem Christie.
All that changed with parabolic skis that only required the rider to shift their knees off-center, rolling them to one side or the other. When it is set to its edge, a deep-cut ski’s tip and tail make contact with the snow. The skier’s weight pushes down the narrower mid-section, which would have normally been several millimeters off the ground in an angled position.
With weight applied, the entire edge makes contact with the snow, but the waist is offset from the tip and tail. That creates a curve in the ski, which is followed to create a smooth, skidless carve.
The change in turning style made expert turns much easier to achieve. Advanced riding no longer demanded advanced technique. Inexperienced skiers gained more speed, control, and responsive turning.
Easier on the Body
The shape of the ski makes turning easier and subsequently puts less strain on your body. With straight skis, you need to exert more energy and strength from your quads to initiate a turn. Depending on your turning style, the twisting of the knees in turning a straight ski can put excess strain on them.
A parabolic ski provides a softer turn and fewer fast adjustments to execute a turn. The skis have a snappier response, making it more natural to bounce back into an S-carve.
Parabolic vs. Straight Skis: Which Should I Choose?
The right ski sidecut depth depends on numerous variables, including your height, terrain preference, and whether you use poles.
In general, if you like bombing groomed hills, a narrow, straighter ski offers stability and speed. In deep snow, you may consider a straight, fat ski or even a reverse sidecut shape. In contrast, beginners and skiers who like a laid-back ride and fluid carves would benefit from the assistive skiing that a parabolic ski provides.
Consider the Sidecut of Your New Skis
Understanding how the sidecut affects turning and control will help you make better decisions when considering parabolic vs. straight skis. But despite its impact, numerous factors can determine how a ski will ride and where it will offer the best experience.
Research skis according to the terrain you enjoy, your body type, and your experience level. If you can’t find the perfect model, wait on investing until you have a chance to rent and test different ski shapes. For more information on ski design and how to choose the right specs for you, check out our post on the different types of skis.