What Are Ski Boots Made of and Does It Affect Your Performance?
Ski Expert Skylar Waggoner overviews some of the materials used in ski boots, their impacts, and the trade-offs associated with them.
The answer is yes—the material in your boots matters—however, one thing to remember is that the top priority in finding the best boot for you is the way it fits. Having said this, boots these days are made of many different materials that have a variety of characteristics that make them useful for different types of design and performance goals. I will be running through some of the more common types of outer shell materials used in ski boots, for what purpose, and how they perform.
Keep in mind as well that many ski boots are made of several materials that may interact together to perform differently than each of the individual materials. This is fairly common in crossover boots that are trying to strike the best balance they can between skiing the best they can while still being as light as possible with a large range of motion for when you are touring or hiking up. An example of this is the K2 Mindbender boot that has a TPU lower shell and an upper cuff made of Pebax Bioresin.
PP or Polypropylene
PP is generally the least expensive plastic and for that reason is often used in entry level price points and youth boots. Although relatively temperature stable in terms of its stiffness and relatively light, the downside of this plastic is its lack of durability and the possibility of deformation or melting from a heat gun or grinder during fitting.
TPU or Thermoplastic Polyurethane (sometimes referred to as PU)
Lower quality PU is usually recycled, but still retains the general performance advantages over PP boots. The downside is limited stiffness and this plastic can only be made in black, but it allows manufacturers to create less waste as well as save on costs. This plastic will most likely be in your entry-level adult boots.
Mid-quality PU which is often PU-ester rises above the recycled PU because it doesn’t have the same limit on stiffness and can be made in multiple colors. This makes it a good candidate for mid to upper-level adult boots.
High-quality PU which is softer PU-ether can be made to have the ideal viscoelasticity for the boot. This means a nice powerful boot that still has a smooth progressive flex pattern. This plastic is also very conducive to fitting such as grinding or punching the shell. This material is often used in very high-end alpine boots such as race boots. Although it is great in a lot of ways, being a PU plastic means it is still heavier, more expensive, and can change stiffness in different temperatures than some other plastics.
Some brands have also developed TPU plastics with unique proprietary formulations that allow the plastic to be more stable across different temperatures, be more moldable, and are able to make lighter-weight designs by using a different durometer (or hardness) and thickness of TPU throughout different parts of the boot. These are still expensive though, and the material itself is still relatively heavy.
PA or Polyamide
In general, polyamides are commonly used in ski boots to save weight without sacrificing stiffness which is needed in crossover free-touring and backcountry boots. There are several types but some common traits include being very expensive, lightweight, and relatively temperature stable.
Grilamid is a brand of polyamide plastic that is commonly used in backcountry boots. This is due to its strength-to-weight ratio. At the same time, there are downsides to this material. Besides the fact that it is expensive, it is also not quite as durable as TPU plastic, and Grilamid also does not have quite as progressive or even of a flex pattern. Oftentimes, these cons are worth the trade when considering the weight savings and strength when it comes to backcountry-specific boots.
Pebax is a brand of Polyether Block Amide (PEBA) which is a thermoplastic elastomer (TPU). This is a lightweight, durable plastic that is affected a lot less by cold temperatures relative to many other plastics. This makes it common on crossover free-touring or backcountry boots. There are multiple formulas for Pebax used in ski boots including some that are partially biobased.
Carbon and Other Composites/Advanced Materials
Carbon and other composites are sometimes used in higher-end ski boots. They are used both as additives to other materials as well as carbon fiber being used by itself for different boot parts. A common example of this is carbon fiber cuffs on free touring and backcountry boots to increase stiffness and reduce weight. An example of using these materials as additives includes Head using plastic with graphene added to it to increase strength and reduce weight allowing other parts of the boot to be thinner without sacrificing stiffness again increasing weight savings.
Aluminum is the main materials companies use for the buckles or hike function of the boot. Sometimes companies will use more expensive magnesium for buckles when they need the weight savings. Other metals in the boot include the steel bolts used to control the stiffness of alpine boots, as well as metal cables used in some boots as part of their buckles or hike mode mechanisms. However, generally, the use of metal on boots is kept to a minimum because of the weight.
Professional boot fitters are a key group of people in the ski industry. Good boot fitters are experts on feet, a wide array of boots from across the industry, making custom footbeds, and the wide variety of methods used to change the fit of a boot. These are the people to see if you have any fit problems with your boots that you need help with. Boot fitters can turn your decent- or ill-fitting boot into a great fitting boot that keeps you out on the hill all day without pain. Obviously, there are some problems that are so bad they can’t be fixed, but if it is possible your local boot fitter is your best hope.
Although all this information is a great reference to have and will give you an idea of the differences that there might be between two boots made of different materials, the type of material is not one of the most important factors when shopping for a boot. As you can see, the cost, type of skiing the boot is used for, and level of performance/skier it is intended for all have an impact on the decision.
I hope this article was helpful and gives you a little better idea of some of the materials used in ski boots, their impacts, and the trade-offs associated with them. Always remember FIT IS THE MOST IMPORTANT factor in finding the right boot for you! All the manufacturers are trying to make the best boot, meaning that as long as you purchase a boot that fits well and is designed for the type of skiing that you do (alpine, touring, etc.), you are going to get great materials that perform the way you need them to. If you have any questions about finding the best boot for you, reach out to a Ski Expert here on Curated! We'd be happy to help. Cheers!