‘I’m a cynic, it’s my job,’ admits dhb’s product manager Ben Hewitt. ‘Material manufacturers come to me and say our fabric does this, it does that, and you take it with a pinch of salt. But the 37.5 material used in the dhb Aeron Storm jacket is scientifically proven to help you perform better on the bike.’
While you may not be familiar with 37.5 the material, no doubt those digits will chime as the figure in degrees Celsius of the body’s optimal core temperature. A couple of tenths either way can be desperately uncomfortable, a few degrees catastrophic. It’s highly unlikely you’ll ever pedal yourself into the absolute red, but it’s safe to say deviations from that golden number seriously inhibit athletic performance.
‘The Aeron Storm isn’t just about being totally waterproof,’ continues Hewitt. ‘It’s also about letting your skin breathe, because if your skin can breathe you can regulate your core temperature, which means you can go harder and faster for longer. A recent study at the University of Colorado showed that a cyclist could spend 42% more time at full gas when his core temperature was regulated with special clothing. And what was in that clothing? 37.5 blended fabric.’
Sands to ashes
The dhb Aeron Storm is made with the tried and tested benchmark formula of a multi-ply laminate, where a durable, fully waterproof membrane is bonded to a breathable inner layer. However, that breathable layer isn’t what you might find elsewhere.
‘The inner layer of the Storm jacket is printed with particles of coconut shell-activated carbon and volcanic sands,’ says Dr Greg Haggquist, founder of 37.5. ‘These particles are desiccant, so they’re trying to dry out their environment. They also have a lot of surface area and absorb energy from the human body.
‘When you ride, you generate a large amount of heat, and to remain efficient and keep putting out those watts your body needs to dissipate that heat. The best way to do this is through evaporation of moisture – sweating. Most people think of sweat in liquid form, but it actually starts off as vapour. It only becomes liquid when the humidity around your skin goes from 65%, where you start to feel uncomfortable, to 85%, where the vapour liquefies because there are more water molecules than the air around your skin can hold. This means there’s a very short window of time during a ride before your increased body temperature leads to uncomfortable sweating and a lag in performance.’
Most waterproof breathable membranes require there to be a relative humidity between skin and jacket of around 75% before the water molecules start pushing their way out, by which point your core temperature is already beginning to rise. To combat this many other manufacturers increase membrane permeability, but this can potentially compromise waterproofing. Luckily for the Storm jacket rider, dhb has found a way to be both highly breathable and fully waterproof.
According to Haggquist, the key to solving this conundrum is to ‘trick’ the Storm’s breathable membrane into believing the humidity is 75% or above whilst leaving the skin happy at a far lower humidity. In short, the Storm lets you sweat like you aren’t wearing it.
‘In order to create this effect we first have to get sweat vapour away from the skin and onto the surface of the inside of the jacket,’ says Haggquist. ‘The volcanic sands and coconut shell particles do this as they love to absorb water. These particles account for only 18g of each Storm jacket’s weight, but that equates to 10,000 particles per skin pore. The surface area inside the jacket is therefore 800% greater than a similar garment’s, so there’s much more of this super-absorbent matter on show to absorb sweat. But if all these particles did was absorb water, eventually the inside of the Storm would saturate and you’d be left clammy and overheating. So stage two is to process those sweat molecules out of the jacket. We do this using infrared light from the body.’
Haggquist explains that any warm object emits heat as infrared light, which has energy. The human body emits this energy on a wavelength spectrum between eight and 14 microns, which normal clothes let through like light passing through glass. The Storm jacket’s lining, however, acts more like a pair of sunglasses, actively harnessing the energy of the infrared light. ‘The energy “excites” the sweat molecules that have been absorbed by the particles on the inside of the jacket,’ he says. ‘This pushes them through the breathable, waterproof membrane, de-saturating the particles so they can absorb more sweat and repeat the process. Your skin remains dry, you stay comfortable and, most importantly, your core temperature is regulated so you can go harder.’
On your bikes
Undoubtedly there’s a lot more to the dhb Aeron Storm than meets the eye, but that technology would be wasted without the correct application, so for the final word it’s back to dhb’s Ben Hewitt:
‘The Aeron range is all about getting out 365 days a year, and the Storm is designed for serious riders looking to put in serious miles on even the darkest winter days. So as well as all the taped seams and the YKK Stormguard zipper we’ve added other neat touches like zip-up vents in the sides of the jacket that double as entry points for your hands to reach your jersey pockets, and what I call “kangaroo” pockets in the drop-down tail at the back, one of which is fully waterproof, ideal for carrying your phone or wallet, for example.
‘All in all it’s been a 15-month project to get the Storm made, and it’s turned out to be the most technically advanced garment dhb has ever produced. Our ethos has always been to make kit that performs beyond its pricetag, as all too often price is a barrier into cycling. That’s why we’re pitching the Storm at £125, which I think is incredible value for what it delivers.’