100 Percent Helmets

How Smartshock Works - and Why It Matters on UK Trails

Most riders know MIPS by name, but 100% mountain bike helmets take a different route. The Smartshock® Rotational Protective System uses a network of suspended elastomers positioned within the helmet's structure rather than a low-friction slip-plane between shell and liner. On an oblique impact - which is statistically what most trail offs look like - those elastomers compress and flex to absorb rotational energy before it reaches your head. It's a mechanical damping approach rather than a sliding one, and independent lab testing suggests it performs comparably to MIPS in rotational metrics.

Underneath that, multi-density EPS foam does the heavy lifting on direct impacts. Different density zones mean the foam responds progressively: softer sections crush first under lighter impacts, denser zones handle the serious hits. The polycarbonate shell keeps the overall weight competitive without sacrificing structural integrity on rocks or roots.

Ventilation is where 100% makes a strong case for UK-specific use. Their open-face trail helmets run 14 to 15-port active ventilation systems - channels that pull air through the front and exhaust heat from the rear even at the grinding pace of a long winch up a Welsh fire road. That matters more than people think. A helmet that breathes poorly on the climb means you're already overheated before the descent starts. The internal channelling is shaped to maintain airflow even when you're barely moving, which is a deliberate design choice rather than an afterthought.

The Range, the Fit, and Picking the Right Lid

The 100% open face trail helmet lineup centres on two key models. The Altec sits at the top - more coverage, more ventilation ports, and a slightly more enduro-focused fit profile that works well for technical, committing riding. The Altis trades a touch of coverage for a lighter feel and suits riders who spend more time on trail centres and cross-country-leaning all-mountain routes. Neither is a compromise; they're genuinely different tools for different riding styles.

Fit-wise, 100% helmets run true to size with a slightly oval internal profile. That suits the majority of British riders, though if you've got a notably round head you might find the fit a fraction snug front-to-back - worth trying before committing if you can. The ratcheting fitment system at the rear lets you dial in tension around the crown precisely, and it holds its setting reliably rather than creeping loose mid-ride. Sizing runs from small through extra-large, so most riders will land cleanly within the range without needing to size up or down.

Looking for maximum gravity protection or youth sizing? Browse our specific 100% Full Face Helmets and 100% Kids Helmets ranges. Neither full-face nor kids models are covered here.

If you're weighing up alternatives, Fox helmets offer a similarly enduro-leaning open-face range, while Bell helmets tend toward a rounder fit profile that suits different head shapes. Giro helmets are worth a look if you want MIPS-specific tech across a wide price spread. The 100% range competes directly on protection credentials and sits confidently in that company.

Goggles, Gloves, and Living With the Helmet All Winter

The multi-point adjustable visor on the Altec and Altis isn't just there to block winter sun - though it does that well on those low-angle January afternoons in the Peaks. It lifts high enough to stow your goggles cleanly underneath during the climb, sitting flush against the helmet without the strap bunching or the lens fogging against the shell. That's a detail that sounds minor until you're three kilometres into a muddy Welsh descent and your goggles are where they should be.

Speaking of goggles - the goggle integration port at the rear of the helmet keeps the strap seated and the goggle aligned. Pair these with 100% goggles and the fit is dialled by design, though most standard MTB goggles with a 45mm strap will work without drama.

The Fidlock SNAP magnetic buckle is genuinely useful rather than just a spec-sheet point. One hand, one motion, even in thick winter gloves - the magnetic guide pulls the buckle into position and it clips with a satisfying click. Releasing it is equally quick, which matters when you're overheating at the top of a climb and want the chin strap off fast. If you're regularly riding in winter gloves, you'll notice the difference over a traditional buckle within a ride or two.

The washable antimicrobial liner is easy to remove and handles a machine wash without losing its shape or loft. Realistically, give it a wash every few weeks during heavy use - British mud has a way of working into every crevice, and a fresh liner genuinely extends the helmet's comfortable life. Check the 100% helmet spares page if you need a replacement liner down the line; they're available separately, which saves you replacing the whole lid.

If you're building out a full protection setup, 100% body armour integrates well with the helmet range for those sessions where the trail demands more than just a lid.