With the launch of the all-new K2 Cortex dual BOA boot, we wanted to learn more about what happens behind the scenes when designing a new boot. We sat down with Christie Burrow, one of the boot designers at K2 who had a big role in developing the new boot (as well as leading the charge on new women’s boot products). If you’ve ever been curious how long it takes to design a new boot, how many samples it takes, and the priorities they have, look no further.
Tell me a little about what you do at K2 and how you got into it.
I’m the lead boot design engineer at K2. I was a competitive swimmer my whole life—that was my main sport growing up and throughout college. In school, I did a project where I presented on how the evolution of sports equipment influenced the progression of athletes, and all the different materials that have been discovered to further performance in sports. In swimming, tech suits use hydrophobic materials to improve performance, increase buoyancy, and decrease drag.
That project got me excited about studying engineering in college, and I wound up in mechanical engineering, minoring in Biomedical engineering. After college, I started working with biomedical devices, then moved to creating wearable communication devices for first responders and the military. We embedded radios and screen-printed antennas in tactical vests and other clothing, so there was a lot of integration between soft and hard goods. Eventually, this job at K2 popped up, and I jumped at the opportunity!
My very first job growing up was ski instructing. I hadn’t really thought about the ski industry as a full time career before, since I was so focused on swimming as my sport. But, I’ve been at K2 for almost three years now. It’s cool that all my life experiences have led to this point.
How long have you been a skier? Did you have boot problems yourself in your ski career?
I’ve been skiing since I was three! There was no ski racing in Maryland, where I grew up. I was just going out with my family, and it was all about the fun, being outdoors, and spending time together. Something I think is cool about our boot team is that we all come from different backgrounds and came into the ski industry with different experience. We are a blend of ski racers, boot fitters, ski instructors, and free skiers who just love and enjoy the sport.
I always had hand-me-downs for boots growing up. The first pair that I got to own was such a game-changer. I finally had proper control and could actually engage my skis. Getting the right pair of ski boots is one of the most important aspects of your ski gear. I think more people are getting behind that now.
Let’s get into boots. What’s the deal with BOA?
My boss always says it’s hard to catch lightning in a bottle. Revolutionary advancements in the ski industry don’t come along that often. Over all the generations of ski boots, they mostly focus on small incremental improvements over time. One consistent thing you’ll see is buckles. People have tried to do different things along the way, but buckles have stood the test of time. So to create a real alternative is an exciting thought.
What’s cool about BOA is that they have all the lab data to show that this is a viable alternative. They’ve fully delivered on the scientific backing to prove their system reduces hot spots, improves fit, and increases performance. We realized it was a lightning in a bottle moment that doesn’t come around that often and new we needed to jump at the opportunity.
What’s the gain of having BOA on the upper cuff instead of just the lower?
We feel like the BOA cuff adds a ton of performance to the boot. Buckles are metal and rigid, so they don’t have any give and can be very restrictive, especially if you don’t get the micro-adjust just right. The BOA system holds tension on the lace, while the lace is free to move between the upper and lower attachment points. As you flex into the front of the boot, the lower lace tensions and the upper loosens, so it’s a much more progressive flex. Plus, BOA improves the wrap around the shin, making the fit more consistent and allowing for a snugger fit without cutting off circulation.
What was the process like designing this new boot? How many test boots do you have to go through before you feel like you nailed it?
The development of ski boots is really interesting. Injection molding is expensive and time-consuming, so you can’t rely on infinite samples. At the beginning of the design process, we’ll work on old shells and make modifications. We’ll dremel old buckles and add new features as a baseline. That helps to give us an idea of where we want to go with design. We also test other competitor models and decide what we like and what we don’t.
As we create the CAD model of the boot, we use 3D printing to assess the design. We can’t ski these boots, but the “shop” fit tells us a lot. We can decide about moving dial or guide locations as well as changes to fit. Once we submit models for molds creation, that’s a relatively final design. When we test those boots, we have a few weeks to make any updates before the next round of injections.
During our first on-snow test in November, we ski the boots to assess ski performance and fit. Day one we might test the same liner between different shells and then the next day vice versa. Our testers are assessing different foams, materials, gender specific features, and other things like that. Then we debrief with every tester and come to some conclusions from feedback that is consistent. Next we decide what our priorities are going forward. That’s where we go through this process of what we can actually solve and improve at this stage of development. We weigh what the safest solutions might be, and the pros and cons of making certain changes.
We’ll complete a similar test in January in order to evaluate the updates as well as starting to figure out the flex profiles and materials required for each model.
There’s also lab testing going on during this time to ensure the boots are safe for our consumers. We want to make sure when you jump off a cliff the boot doesn’t explode, and we can rely on the product to support us for a long time. Most of these tests are created using K2’s own strict internal standards, as there are very few regulatory standards for ski boots. We’ll take other competitor’s boots and put them through the same tests to make sure we meet or exceed the standards of our competitors. The lack of regulation always surprises me coming from my military experience. We take on a lot of the regulation ourselves.
After all that, we go into grading. Most brands create a product using only one size. We start with two sizes because we have a female engineer (me). At K2, we start with a 23.5 and a 27.5. We’ve started grading women’s boots off the 23.5 and men’s off the 27.5. By grading the women’s boots from a 23.5, we are greatly reducing the scaling factor, allowing for a more accurate fit.
What goes into finding the “flex” rating?
At the factory, we have tons of materials to choose from. We’ll usually start with what we think is the highest-performance option, since that is the most likely to cause problems during the demolding phase of the injection process. After the first test, we’ll narrow in on our stiffest flex and maybe make it stiffer or softer. It’s a bit of a guessing game at first, and we usually overshoot one way or the other. During the second on-snow test, we’ll inject a wider range of materials to calibrate all the boots in the model line.
How do you balance out-of-the-box comfort, while also fitting for performance?
This comes back to our diverse team and people from different backgrounds. All the boots in our line attempt to accommodate different skiers. We try to put ourselves in the shoes…or boots?…of who is going to be skiing that boot. For example, the liner of a BFC 130 is a little stiffer and snugger, in order to satisfy a skier who needs a higher-performance boot but with a higher volume fit. Where the BFC 95 is designed for the person who wants to cruise and be comfy. As the flexe goes up, we’re looking for more performance. That then scales even more as we transition into mid-volume and low-volume boots. By delivering the right features to the right people, we can give them the performance they need while being in a boot that feels right out of the box.
When I picked up the Cortex, one of the first things I noticed was how heavy it is! It feels like a lot of downhill boots have gotten away from heavy rides. What’s the goal behind that?
Internally, we call Cortex the “anti-race” boot. We’re not a race brand, we don’t sponsor racers, and that’s just not us. But we saw a missing segment in the market for a low-volume, high performance boot, that didn’t need to be race-oriented. So we created a heavy, thick-walled, supportive boot, for that high-performance all-mountain skier that’s not just looking to carve.
What’s your favorite feature of the new Cortex boot?
Probably the double BOA. Again, it’s just one of those special things that come along.
This was one of the first boots we made with the 23.5 as a sample size. During testing, the boys loved the boot, but the girls were like “we’re not feeling what you’re feeling”. We actually wound up scrapping the original 23.5 boot and starting over to redesign from the ground up on that size. We learned so much from this process and it’s gotten us to reevaluate how we grade our boots. It’s hard to catch every little detail in every size. So, we’re spending a lot of time 3D printing each size, evaluating them with different shaped feet, and focusing on making sure everything is dialed in before the molds are created.
Grading itself is not the perfect solution for designing footware, but it’s impossible to make the boots from scratch in each individual size. Every improvement we can make to this process is going to benefit the consumers who fall outside the sample sizes.
I’m really excited about the growth of some stiff, premium flexes for women in K2s line with several 125 options. Do you think the hurdle is boot fitters feeling confident about putting women in that boot, or do you think that maybe lady skiers are hesitant to bump up to that flex class?
I know several men who are skiing 130s who shouldn’t necessarily be, and I know several women who are probably under-booted. I think it’s a little bit of both. Knowing what’s right for you is tough and not everyone has the luxury of testing boots before they buy. We have heard again and again from our female consumers that people want 21.5s and high flexes. I feel like we’ve started to take those things into account, and now that we’re starting a deeper dive into designing boots for women, I believe we’ll keep going in that direction.
Hopefully, we become a market leader. K2 can’t sell everyone a boot. We can only make so many boots in a year, and sometimes there might not be an option in our line for someone. If we are successful with our women’s product, it will push these other brands to step up their game as well, providing more options for more people. As the women’s boot market grows, I think we’ll start to see more women confidently repping high flexing boots.
We’ve seen the progression from buckles to BOA, to double BOA now. Where do you think boot design is headed next? More BOAs?!
You might see it! I think there are big things to come with customizable liners. We’re starting to focus a more on liners at K2 since we’ve noticed the performance and fit can change so much with the right liner. Continuing to work on our grading and design process will change the game for not only women’s fit but the fit across all sizes.
To wrap things up…I have some hot-take questions:
Powder or corn?
Powder!
Favorite chairlift snack?
Kit Kats.
First chair or last chair?
Last chair.
What’s your local hill?
Stevens Pass, I ski instruct there with 4-7 year-olds. It’s a lot, but it’s a ton of fun and very rewarding to bring so many new people into the sport I love so much.
