The Troy Lee Designs A3 Mips is a premium open-face mountain bike helmet built for riders who want deep trail coverage without moving to a full-face lid. It sits in the serious trail, enduro and eMTB space, with Mips rotational protection, EPS and EPP impact construction, a Fidlock magnetic buckle, a 3-way adjustable visor and enough ventilation to make it viable for long climbs as well as faster descents.

This review of the Troy Lee Designs A3 Mips comes from riding with the helmet on real UK trails, where fit, airflow and comfort matter more than a feature list. A helmet can have excellent safety credentials, but if it feels hot, awkward or distracting, riders will quickly stop reaching for it. The A3 does a lot right. It feels well designed, it has plenty of ventilation and it gives the secure, wrapped feel many riders want from a proper trail helmet.

My initial concern was comfort over longer rides. After spending more time thinking about the fit, it is fair to say the Troy Lee Designs A3 is more particular than poor. This is a deep-coverage helmet with a substantial fit system, lots of padding and a very secure feel. When dialled in properly, it makes sense. However, it is not the lightest helmet in the category, and the brow pad and sweat-management strip may not suit every rider. That makes it a very strong trail helmet, but not necessarily one that disappears on every head shape in the same way.

For riders comparing premium trail helmets, it sits in the same conversation as the Bluegrass Rogue Core Mips, Canyon Deflectr and Specialized Ambush 3. The difference is that the A3 feels more traditional than the Canyon, more substantial than some lighter trail lids and more coverage-focused than most budget MTB helmets. Or, if you’d like a wider look at trail helmets, take a look at our best MTB enduro and trail helmet buyers guide.

Troy Lee Designs A3 Mips: Review

Comfort and fit

The Troy Lee Designs A3 Mips has a very secure, wrapped feel. It is not a barely-there XC-style helmet, and it does not try to be. This is a deeper-coverage trail helmet built to sit low around the back of the head and temples, which immediately gives it a more protective feel than lighter, airier helmets.

Once the fit is dialled in, the A3 feels stable and well supported. The V3 precision fit system gives useful height adjustment, and the rear dial is easy to use. It is the sort of helmet that rewards taking a few minutes to get the setup right. Cradle height, strap position and pad choice all matter here, because the helmet has a substantial internal structure and plenty of padding.

That is also where the comfort question becomes more nuanced. The A3 is widely praised for comfort, and it is clear why. It has a plush, premium feel and does not move around on rough ground. However, for my head shape, it did not quite disappear in the same way as the very best-fitting helmets I have used. I suspect that is more about fit and setup than a fundamental flaw, but it is still worth noting because helmet comfort is deeply personal.

For eMTB riding, the secure fit is a major plus. Electric mountain bike rides often involve longer climbs, repeated descents and rougher trails taken at higher average speeds, so a hel

met needs to feel planted without being overtightened. The A3 does that well. It feels like a helmet designed for proper trail riding rather than casual off-road use.

Ventilation and trail performance

Ventilation is one of the A3’s strongest areas. With 16 vents and internal channeling, it moves air well for a helmet with this much coverage. It does not feel like a stripped-back race lid, but it is impressive for a deep trail helmet.

On climbs, the airflow is noticeable enough to stop the helmet feeling stuffy. That matters on an eMTB because motor support does not remove effort completely. On technical climbs, slow woodland sections and repeated trail-centre laps, you still work hard and build heat. The A3 handles that better than its substantial shape might suggest.

The Fidlock buckle also helps day-to-day usability. It is easy to fasten, simple to release and works well with gloves. It sounds like a small detail, but it is one of those features that makes a helmet easier to live with, especially when your hands are muddy, cold or tired after a long ride.

The visor is another strong point. The 3-way Magnajust system gives useful adjustment, and the magnetic positions make it feel more refined than a basic plastic peak. It also gives space for goggles under the raised visor, which is useful for riders who move between normal trail rides, wet winter conditions and more aggressive bike-park-style riding.

Protection and coverage

The A3 is clearly built around coverage and protection. Troy Lee Designs uses dual-density EPS and EPP construction, with B-Series Mips for rotational impact protection. The helmet also sits deeper than many open-face trail lids, extending further around the back of the head and temples.

That deep coverage is one of the main reasons the helmet feels so confidence-inspiring. You do not get the chin protection of a full-face helmet, of course, but for an open-face trail and eMTB helmet, the A3 feels substantial. It is the sort of helmet that makes sense for riders who push beyond gentle trail-centre loops but do not want to wear a full-face lid all day.

No helmet can remove the risk from mountain biking, and fit still matters more than any individual feature. But the A3 has the right safety ingredients for serious trail use: deep coverage, secure retention, rotational impact protection and a shell construction designed to deal with different impact speeds.

For riders who regularly ride heavier full-suspension eMTBs, that protection-first feel is reassuring. The extra mass and speed of an eMTB can make descents feel more committed, and a helmet like the A3 feels appropriate for that style of riding.

Design, visor and eyewear compatibility

Troy Lee Designs helmets have always had a strong visual identity, and the A3 continues that. It looks premium, purposeful and unmistakably trail focused. The shape is more substantial than some competitors, but it avoids looking oversized once on the head.

The visor is one of the best-designed parts of the helmet. It is easy to adjust, has a secure magnetic feel and sits high enough to work with goggles. The smart shear screws are a useful safety detail, designed to prevent the visor causing unnecessary damage to the helmet in a crash.

Eyewear compatibility will depend on the glasses. Some riders will get on with it perfectly, while others may find that certain riding glasses do not sit quite as neatly with the shell or straps. That is not unusual for deep-coverage MTB helmets, but it is worth checking before buying if you have a favourite pair of glasses you always ride in.

The overall design feels well considered. The A3 is not trying to win by being minimalist. It is trying to give trail riders a feature-heavy helmet with strong coverage, good airflow and premium finishing details.

Weight and brow pad

The main drawback is weight. The A3 is not excessively heavy, and the weight is managed well once the helmet is properly fitted, but it is not one of the lightest open-face MTB helmets. That is the trade-off for deep coverage, dual-density construction, Mips, a substantial visor system and the amount of padding inside the helmet.

Some riders will not notice this at all. Others, especially those coming from lighter trail or XC-style helmets, may find the A3 feels more present on the head over long days. It is not uncomfortable in a general sense, but it is a helmet you are more aware of than some lighter options.

The Sweat Glide brow pad is the other point to consider. The idea is sensible: help manage sweat and keep it away from the eyes and glasses. In practice, brow pad design is personal. Some riders will appreciate it, especially on warm climbs. Others may find the feel of the strip more noticeable than a standard pad setup.

The good news is that the system is removable, so riders have some flexibility. But it is still worth mentioning because this is one of the few areas where the A3 may not suit everyone straight away.

What is not so good?

The Troy Lee Designs A3 Mips does very little badly, but it is not perfect. The first issue is weight. It feels secure and protective, but it is not the lightest helmet in the premium open-face category. If your priority is a barely-there feel for long summer rides, there are lighter options.

The second issue is the brow pad and Sweat Glide system. It is a clever idea, and it can work well, but it may not suit every rider’s forehead shape, sweat pattern or eyewear setup. On a helmet with such a premium finish, that small comfort detail matters.

I would not mark it down for ventilation. For this level of coverage, the airflow is strong. Nor would I make price the main criticism, because current discounts make the A3 far more attractive than its original RRP suggests.

Final verdict

The Troy Lee Designs A3 Mips is a very strong open-face MTB and eMTB helmet. It is well ventilated, secure, feature-packed and designed with the sort of coverage that makes sense for proper trail riding. The Fidlock buckle, adjustable Magnajust visor, goggle storage and Mips protection all add to the premium feel.

The only caveats are weight and the brow pad setup. It is not the lightest helmet in the category, and the Sweat Glide brow system may not suit every rider. But those are relatively small criticisms against a helmet that otherwise feels extremely well designed.

If you want a deep-coverage trail helmet for eMTB riding, trail centres, natural woodland routes and faster descents, the Troy Lee Designs A3 Mips still makes a very strong case for itself. It is not the newest helmet on the market, but it remains one of the most complete premium open-face options, especially when found at a strong discount.

Troy Lee Designs A3 Mips competition

Troy Lee Designs A3 Mips – FAQs

Is the Troy Lee Designs A3 Mips good for eMTB riding?

Yes. The Troy Lee Designs A3 Mips is well suited to eMTB riding thanks to its deep coverage, secure fit, Mips protection, strong ventilation and goggle-compatible visor. It works well for trail centres, woodland rides and faster descents.

Is the Troy Lee Designs A3 Mips well ventilated?

Yes. The A3 has 16 vents with internal channeling, and it feels well ventilated for a deep-coverage trail helmet. It is not an ultra-light XC helmet, but airflow is strong for its category.

Is the Troy Lee Designs A3 Mips comfortable?

Yes, provided the fit suits your head shape and the helmet is adjusted properly. It has a secure, padded and premium feel, although some riders may find it more noticeable than lighter helmets over long days.

What is the main drawback of the Troy Lee Designs A3 Mips?

The main drawback is weight. It is not the lightest open-face MTB helmet, and the substantial construction can make it feel more present on the head than some lighter alternatives.

Does the Troy Lee Designs A3 Mips work with goggles?

Yes. The A3 has a 3-way Magnajust adjustable visor and goggle storage under the raised visor, making it suitable for riders who use goggles on faster or wetter rides.