Best mountain bike helmets: 5 picks for UK trail riders

Five helmets, five jobs — start here if you want the short version.

• Best overall: Fox Speedframe Pro — the trail helmet that suits most riders in the UK, from a trail centre lap to a full day in the hills.
• Best budget: Specialized Align II MIPS — a proper trail shape, a dial fit and a slip-plane liner without a big spend.
• Best for aggressive trail and enduro: Troy Lee Designs A3 — deeper coverage at the back and sides for riders who push on descents.
• Best ventilated: Smith Forefront 2 — for hot days, long climbs and riders who overheat easily.
• Best convertible: Bell Super 3R MIPS — open-face for the climb, chin bar for the descent.

All five are open-face or convertible helmets you can pedal in, and all have a retention system you can adjust with one hand. Prices move around with colourways and sales, so shop around; the notes below are about what each helmet is actually like to live with.

The pattern is simple. Ride mostly undulating trail and the Fox or the Smith will do everything you need. Ride steep, rooty tech most weekends and the A3's coverage is worth the bulk. If your days end with a lift back to the top, the Bell saves you buying two helmets — as long as you accept it isn't a downhill lid.

Every helmet sold in the UK has to clear the same minimum standard, so the differences worth paying for are the ones you notice on the bike.

• Coverage. The back of the head and the temples are where trail helmets earn their keep. Look at how low the shell comes down at the rear.
• Fit and retention. A dial that wraps the whole head beats a basic ratchet, and pads in different thicknesses help. Try the helmet with your hair the way you actually ride.
• Ventilation. A more open shell means cooler climbs, but also more mud, water and insects inside.
• Visor. An adjustable peak is worth having for low winter sun and for pushing goggles up out of the way.
• Eyewear compatibility. Take your glasses or goggles to the shop — a helmet that pinches the arms of your glasses is unbearable after an hour.
• Weight. You notice it at the end of a long day, but not as much as fit.

MIPS (Multi-directional Impact Protection System) is a thin low-friction layer inside the helmet that lets the shell rotate a few millimetres against your head in an angled impact — the kind you get when you land shoulder-first on a root. It's the most common add-on in this list, and it now appears on budget helmets as well as premium ones.

Koroyd works differently: it's a structure of welded tubes, used by Smith, that crushes in a controlled way on impact. Some helmets combine it with MIPS. Other brands use their own versions — SPIN pads at POC, Turbine at Leatt, WaveCel at Bontrager — and they all aim at the same problem.

None of it replaces coverage and fit. A helmet with every technology going but the wrong size is not the safer choice.

Most British riding sits somewhere between a trail centre loop and a natural bridleway, which is why a trail helmet with deep rear coverage is the default choice. Match the helmet to your hardest regular ride, not your easiest.

• Cross-country and marathon: the lightest, most ventilated open-face helmets with less rear coverage. Fine on fast, smooth courses; less forgiving when it gets steep.
• Trail and all-mountain: the sweet spot for most riders — deep rear coverage, dial fit, a peak you can move.
• Enduro: more coverage, a bigger visor and room for goggles; a convertible starts to make sense here.
• Bike park and uplift days: a full-face or convertible, and if you're riding fast lifted terrain look for ASTM F1952 certification.
• E-bikes: a legal 250W, 15.5mph e-bike is fine with a normal trail helmet; a speed pedelec capable of 45km/h should be paired with a helmet tested to NTA 8776.

Sizing is by head circumference, measured around the widest part of your head, just above the ears. Most brands cover roughly 51–63cm across their size range, but shapes differ: some are rounder, some narrower front to back. If you're between sizes, try both.

Once it's on:

• The front edge should sit about two fingers' width above your eyebrows, not tipped back.
• The retention dial should be tight enough that the skin on your forehead moves when you rock the helmet, without pressure points.
• The chin strap should sit just under your jaw with the buckle flat, and the splitters should meet just below the ear.
• Push the front of the helmet up and back — it shouldn't move far enough to expose your forehead.