GROUPTEST TRAIL HELMETS

Nine open-face lids tested for coverage, fit and comfort, so you can hit the trails confident your bonce is protected

- LUKE MARSHALL

MEET THE TESTER

LUKE MARSHALL

TECHNICAL WRITER

Luke has been hitting mountain bike trails for the past 25 years, from racing World Cup DH in the 2000s to competing in the Enduro World Series last year. He's never happier than when riding rough, rowdy trails, which puts him in the perfect position to know what makes a good lid, and to put this lot through their paces.

A helmet is the most important piece of cycling equipment you'll buy. While they're not always the most exciting or drool-worthy items of kit, it's crucial to find one that fits well and offers plenty of protection - it could save your life!

So, how do bike helmets actually work? First, they spread the impact force over a larger area - something that's especially important if you hit a sharp rock, for example - and then they slow it down, causing it to take milliseconds longer to reach your head. This smooths out and reduces the peak impact spike that, in the worst case, can cause brain damage. That fractional delay may not seem like it'll make much of a difference, but does.

Inside every helmet is an expanded foam (EPS) liner, designed to crumple to destruction to extend the impact time. Many brands now use different foam densities to make this even more effective. Koroyd 'straws' are another recent development -thin plastic cylinders designed to deform on impact, spread the load and reduce that peak 'impulse: Rotational forces can be dangerous, too, though, which is where tech such as MIPS (Multi-directional Impact Protection System) comes in. To combat your head being forcibly twisted, the various MIPS set-ups and competing designs allow for some rotation between the liner and the helmet pads. Not all lids have this extra safety tech, but there's usually a small sticker (yellow, in the case of MIPS) that'll tell you if it's there.