Gold Skis – How Ski Equipment Decides Winners in Cross-Country Skiing and Vasaloppet

The past few weeks have been a dream period for cross-country ski fans, with both the World Championships and the legendary Vasaloppet delivering unforgettable racing. What a set of performances we’ve seen: Klaebo’s six World Championship golds, Alvar’s Vasaloppet victory, Jonna’s domination in the sprint and decisive legs in the relays, Ebba and Johaug’s second-by-second duels, and finally Frida’s ice-cold finish over the 50 km.

What all these achievements have in common is simple: none of them would have been possible without “gold skis”. In today’s extremely tight cross-country skiing, nobody wins without competitive equipment. This doesn’t mean you must have the absolute fastest skis on the day, but you must have skis that are competitive relative to your own capacity. A stronger skier can sometimes cope with slightly slower skis, while others really need top-notch material to stand on top of the podium. Performance is truly a combination of the skier’s output and the waxing team’s work. It’s no surprise that waxing teams invest enormous effort in skis, structure, and glide.

Why Fast Skis Are About More Than Just Waxing

Having fast skis is of course partly about craftsmanship in the wax cabin, but just as much about being able to select which skis and setup run best on the day. That is fundamentally a question of measuring small differences. Measuring differences and making the important things measurable is exactly what we at Skisens are passionate about, so this topic is very close to our heart.

So how do you actually measure glide, and what kind of precision is required? In elite ski racing, margins are razor thin. As an example, the 1.3-second gap between Ebba and Johaug in the 10 km race corresponds to roughly a 0.2% difference in glide friction (you can read more about this calculation here). If we, for simplicity, focus only on glide and ignore grip, a 0.2% difference is extremely small—probably below what any waxing team can reliably guarantee.

How Glide Tests Are Done in Practice

To understand just how small these margins are, it helps to look at how a glide test is actually performed. Last autumn, Skisens had the opportunity to participate when the Swedish Ski Association conducted tests to update its guidelines for roller-ski wheels. You can read about the test procedure in their report on the Swedish Ski Association’s website: Testrapport rullskidor SSF.

In that project, rolling resistance was measured in three ways: with a dedicated measuring instrument, with Skisens poles, and with conventional paired tests — the most common method used to choose skis on snow.

During the paired tests in Falun, the same two test skiers repeated runs twice, and glide was compared over a 100-meter glide section with an entry speed of about 35 km/h. The results showed that a difference of 100 cm in glide distance corresponded to roughly a 10% difference in glide friction. This means that if we want to select a pair of skis that are only 0.2% better than another, we would need to detect glide differences on the centimeter scale. For anyone who has done glide tests, that feels almost impossible.

In fact, the standard deviation between two repeated runs on identical skis in this experiment was 37 cm over 15 repetitions, even though the test skiers were experienced athletes competing at a high national level.

Small Measurement Errors – Big Time Differences

According to the calculations above, 37 cm corresponds to about a 3.7% difference. If we translate that into race time over 10 km under the conditions that prevailed in the 10 km World Championship race in Trondheim, that could mean around 30 seconds of difference. By repeating the glide tests many times, you can reduce some of this uncertainty, but it is extremely difficult to get below 10–20 cm of measurement spread. That still leaves an uncertainty of roughly 10 seconds over 10 km — which is more than the gap between first and second place in both the men’s and women’s races in Trondheim.

Everyone who has carried out glide tests knows how difficult it is to choose skis with this level of precision. It is very common to experience different results in repeated testing. One of the main reasons is the challenge of ensuring identical entry speed into the glide section.

Figure 1 shows how glide distance in a glide test with skis that differ by 5% in glide friction is affected by variation in entry speed. With identical entry speed, the difference in glide distance after 100 meters is around 0.5 meters. However, it is also clear that variation in entry speed influences glide distance more than the friction itself. If the slower skis start with an entry speed that is 1 km/h higher, that speed difference will have more impact on the outcome than the 5% friction difference. To choose the right skis, you have to look closely at how the glide of the two pairs develops throughout the test. Experienced testers are very skilled at this, which is why most teams still manage to select competitive skis so that we as spectators get to see fair competitions.

Relative vs Absolute Measurements – The Future of Fair Skiing?

To fully understand how much work waxing teams must put in, it’s important to stress that all of their testing is based on relative measurements — that is, comparing different skis with each other. This is incredibly time-consuming and never reveals how close the result is to an ideal target. A dream scenario would instead be to work with absolute metrics, such as direct measurements of glide friction.

With full respect for how complex true craftsmanship is, the ability to measure glide friction could, over time, build a knowledge base of what friction levels are achievable in different conditions. It would also create transparency around how good the skis of different teams really are. In the long run, the sport could perhaps adopt an open testing system similar to fluor testing, where the friction of competition skis is documented. This would likely lead to a fairer sport where even smaller federations are given the chance to compete on equal footing with the big nations.