How Rocker Affects Ski Length

“What length ski should I buy?” It’s a question we hear more than almost any other heading into each new ski season. Since the advent of fat skis and raised tails—two key factors that can dramatically alter a ski’s running length and surface area—the answer has been an ever-changing target. And over the past few years, yet another variable has entered the equation: rocker.

Before choosing a rockered ski size, an understanding of how this technology works is key. Rocker basically creates a pre-bent ski. BD skis use this technology in the forebody of the ski, where it sets the ski into an ideal shape for soft-snow flotation. The resulting early-rise tip allows you to float easily over powder and crud, and drive the ski more aggressively in soft snow conditions—much like you would on-piste—without worrying about over-flexing the tip. Rocker makes turn initiation smooth and effortless in soft snow, and allows the ski to change direction far more quickly than traditional camber designs.

The beauty of rocker is that it also can help on firm snow. Due to the early rise tip, the ski has a shorter contact length because the longer tip is raised off the ground. This gives you both the mobility and quickness of a shorter ski on hard snow and the soft snow stability of a longer ski. For example, the 188 Megawatt has a true contact length of 127.7 cm on hardpack—compared to a more traditional 170 cm Verdict that has even more contact length at 132 cm! This is what makes the longer Megawatt totally skiable by someone around 160 lb who normally wouldn’t ski anything longer than 180 cm.

Some things to consider:

• What length do I normally ski with traditionally shaped tips and tails? You can usually go 5-10 cm longer in a rockered ski.
• Am I counting grams of weight, or the size of the cliff? The more aggressively you ski, the longer you can go.
• When in doubt, size up!

Not all rocker is created equal. Each rockered Black Diamond ski has a different amount of tip and running length, which affects what size is best for you. See the chart below to get an idea of running length and tip rocker comparisons:

Note: The Justice has less rocker than the narrower Zealot because of its softer tip, which flexes more than the Zealot’s and effectively gives the Justice more rocker while skiing.

Example: I am 5’8”, 160 lb and I normally ski a traditionally shaped 100 mm waist, 180 cm ski every day because that platform allows me some slop in my balance and makes for easy recoveries, yet is agile and maneuverable in everything except awful wind crust. My fat powder ski is the Megawatt. The surface area and length of the 178 cm is more than enough for me for all types of skiing. I would ski this length even if I were another 15 lb heavier since my height isn’t creating a weird pendulum effect over the fat tip of this ski. And I choose that 178 especially if I’m using it for touring due to the lighter weight. But the running length of the 188 cm is just 127.7 cm, and I opt for this length when I want to gas it and ski aggressive lines.

The skinnier Justice is similar, except the surface area supporting my weight is slightly less. I would opt for the 185 cm Justice in most instances because I’ll ski it aggressively. I could definitely use the 175 for my touring ski, or for a more playful freestyle type ski, but would not be comfortable at high speeds running out a bigger line. And being that it is quite light, the 185 cm is both my touring and inbounds length of choice.

Recent Talk (1)

• Dan T
  21 Oct 2009, 6:58PM

  Thanks for the rocker article. It's great advice and I plan on saving it for the point and time I can afford a larger quiver. Right now I'm torn between Lou Dawson (cheek high ski for his weight) advice and this advice on a 100mm waisted ski. I'm actually looking at the traditional ski referred to above right now. I found the 08/09 Verdict 170's cheap at a place that will take them back. They come to my forehead. I'm 5' 9.5" and a fit 180lb. After reading the above article, I'm comfortable I should have the 180's instead. I need to be real comfortable with this decision because I can't afford 09/10 180's, but can find some 08/09's at a discount- they're just not returnable if they don't work. Do you guys know of any good deals on last year's Verdicts?

• Alex Nagy
  22 Oct 2009, 5:41PM

  Happy to see you finally listed a tutourial/primer in your early rise rocker technology. I have also seen rocker described in a two number formula in some mags. sort of like a rise over run. My question. I am a east Coast skier 155-165lbs( depending on winter beer consumption and skiing pack on or off) With the low running length of the megawatts could a 188cm work in the tight trees of northwestern maine/ Vermont? Or should i ski the 178. My current set-ups are a 2005 Havoc in a 173? or 175. 2008 Coomba in a 174 which sometimes feels unstabile fore/aft. I am a A.T.er and would probably mate the megawatt to either Duke of Fritch. P.S. the Havocs still have camber in them after 4 yrs. and probably 120-160 days. Solid ski but I'm glad you guys made the switch to all wood. P.s.s. I am considering this ski for the deepest of the deep like the saying goes buy a ski for the powder day you dream of. We dream a lot over here in Maine. Thanks hope to hear from ya Aloha.