Helmet Sizes: Less is More... Dangerous

The following is the first in a series on helmet fit and our adventure to create the PerFit System. It all started in the spirit of improving safety, but ended up becoming central to everything we do at KAV.

Buying a Helmet
I live in Redwood City, California, smack between the San Francisco Giants and the San Jose Sharks. There are a few great local bike shops, but trying on helmets felt unsanitary in the early months of COVID. Nevermind that I have kids and have gone through the whole head lice thing more than once. I found a Specialized Evade, but black was out of stock. My days of making a color like "Acid Lava" (a retro yellow sandwiched between an off orange) work are long past me. So onto the internet, where I comparison shopped, figured out who would offer free shipping, and clicked buy. An email explained that it was back-ordered for two weeks. At least I knew it would fit my noggin when it eventually arrived. You've probably had similar experiences. However, if you had a great helmet buying experience, I bet you still have a fit issue, even if you're not aware of it.

road bike bicycle helmets
I'm a Size Medium
The strange thing is when I buy shoes, there are a dozen sizes and half sizes and multiple widths to accommodate my feet. I'm a size 9 EE, or sometimes a 10 D; it all depends on the brand and shoe type. Size your skates down a size or two, running shoes need a bit of room at the toe, climbing shoes need to be snug unless you want to fall into the abyss below and so on. The actual sizing varies, but at least I can get something that fits well. In helmets - I'm a medium. Why? Because a small squishes my head and my head swims in a large. So it's not that a medium fits; it's the others don't. It's an anti-goldilocks moment. It's not an "ah just right" moment; it's just clearly not the other sizes. Don't even get me started when I was on a budget and had to choose between S/M or M/L options.

Why Helmet Fit is Critical
Why is this essential? Well I'm going to come at it with the assumption that we can agree that your head is the most important part of your body. Someone out there will disagree and I'll preemptively concede that I'm not giving up my heart anytime soon, and my hands are, well handy. So why the head:

  • Aesthetics. Your head is the first thing people see. Do you want a helmet that's bigger than it needs to be to get your noggin into it? There's a reason people enjoy wearing fitted or well-tailored clothing.
  • Comfort. Like a tailored garment or a nice pair of gloves, a well fitting helmet just feels so much better. No pressure points. No wobbling. The helmet just disappears while you play.
  • Safety. Do you want your helmet to fall off or shift erratically on impact. If the helmet is "oversized", it doesn't fit well, or you're relying on a tiny plastic retention band to keep your helmet in place during an impact. A well-fit helmet, will perform as designed. 

Our Initial Fit Solution
So when we first started prototyping the KAV H1, we decided why not provide ten sizes of helmets or 53-62cm in 1cm increments. We tested this out on some local hockey players and found this provided a nice fit. Players who fit a 59cm helmet found 58cm too tight and 60cm too loose. They could discern half sizes, but the difference between 3 and 10 sizes was already night and day.

But before we went into production, we found that an Asian player surfaced a significant shortcoming. In hindsight, it's pretty obvious.