With all the biomechanical talk of the last few articles Ray, our Bootfitter and Industrial designer, was feeling a bit left out and I could sense that he wanted to spew forth some techy techy stuff about boots. So, I’ve let him have the reigns on this one. (Under close supervision…)
We all know that “Oils ain’t Oils” and let me tell you: plastics ain’t plastics. To the uninitiated there is an infinite number of plastics out there, all with their own brand names and grades. But as far as ski boots are concerned, we only really care about three types of plastics, and even then there’s only really two that really matter (to the more enthusiastic bootfitting nerds among us). We’re not going to get too techy because the world of plastics is enormous, complicated, varied, won’t help you much and it’s a deep rabbit hole to go down accidentally… so we’ll talk about the generalities of plastic only.
Let’s start in the middle, because that’s probably 80% of the skiing world. Polyurethane is the boot plastic of choice, its key qualities are: rebound, mouldability (holds a punch) and it grinds well. As a general rule, the downside is that its stiffness changes drastically with temperature, so make sure your bootfitter understands this and takes it into account. A floppy boot in Spring is as comfortable and effective as a sofa bed mattress.
A lot of touring boots are incorporating Polyamide (nylons). This makes them much lighter, more expensive and slightly different to work with as far as expanding and grinding is concerned – a good bootfitter should understand this.
Race boots most often use Polyurethane-Ether, an expensive Polyurethane blend.
The other thing to take into account regarding plastics in ski boots is: how much plastic or how thick is the plastic in your boot?
The big thing in boots at the moment is making boots lighter. You can do this by using more high-quality plastics (more expensive) or you can use less plastic in each boot (cheaper). Both approaches have challenges.
World Cup boots, or race boots in general, will have a fairly uniform and thick wall plastic. This makes for a stiff boot with great rebound characteristics and feel and response in all directions.
To decrease the weight of a boot, the manufacturer will often remove plastic from areas of the boot that are not supporting the key directions of force in a ski boot, ie. forwards and to the inside edge. This is great for most people, the downside is that if you need to expand or modify these boots in any way you can have a noticeable effect on how the boot skis, and in some cases cause the boot to ‘collapse’ as the shape becomes critical to how the boot supports you.
Make sure your boot fitter has a plan for any mods they expect to make to your boots and that the boot they choose for you can accommodate these modifications.
If you want to go real deep, listen to this Blister podcast with Matt Manser, Atomic boot designer in Austria. They deep dive into plastics and get really nerdy and detailed. It’s bloody great.