Shape and sidecut were about the last ski characteristics the industry paid attention to- but when they did, they went to town. Ski shapes changed only gradually over 50 years as manufacturers played with stiffness, flex profile, camber, materials, vibration control, and mass before they finally got around to trying new shapes.
These days shape is about the biggest determinant of a specific ski’s function and performance on the hill. You can choose a wide, straight shape for skiing fast in powder, or a narrow, deep-sidecut shape for slashing carved turns on hard snow- and just about anything in between.
But even within a single category, shapes vary- so what difference do those more subtle variations make? How do they change ski performance and function?
Tip and Tail Width: Some companies (notably Dynastar and K2) generally build skis with relatively wider tips than tails- 10mm or more. The wide tip floats better in soft snow, and pulls you into a carved turn, while the narrower tail releases from the turn and skids more easily. This shape allows you to ski more in the fall line, and will be more stable in long turns at speed- preferred by all-mountain skiers for versatility.
Other companies make models with relatively flared tails- less than 10mm narrower than the tip. This shape is better for packed snow carving performance- the wide tail slingshots you through the end of the turn and across the fall-line. It can also work really well for arcing turns in supportable crud or spring snow. These skis will be trickier to skid, and that wider tail can make the tip prone to diving in soft snow- since it will float more, it’ll also push you forward, and the tip down. Most park skis tend towards this shape for better carving in the pipe and initiating spinning tricks.
Overall Width: At the extremes, the widest skis (over 100mm underfoot) are pretty much powder-specific, while the narrowest (sub-70mm) are essentially hard-snow specific. In between lie the skis that most of us use every day: all-mountain skis… but there’s a big difference between a 75mm-waisted all-mountain ski and one that’s 90mm underfoot.
Most importantly, more width = greater floatation, which means easier skiing in soft snow, but width also changes how skis work on the packed. The wider they are, the slower the transition from edge-to-edge, and the further you have to angulate your leg to get the ski tipped up on edge. This makes for more sluggish transitions on packed snow, and the wider skis can be difficult to carve for more conservative skiers. On the plus side, the wider skis offer a larger, more stable platform on any snow surface, and they skid more predictable in the steeps.
Less width = more precision and quicker transitions on the packed snow, and a more demanding ride in the soft stuff.
If you understand how ski shape affects performance and function, it’s a lot easier to narrow down your choices when there are all-mountain skis with a wide spectrum of different shapes.