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Trek Circuit WaveCel fitted

Trek’s Circuit WaveCel helmet is packed with features, but a few issues hold it back

Integrated light mounts are a welcome inclusion even if WaveCel will split opinions.  

Alex Hunt
by Alex Hunt 21.11.2024 Photography by
Alex Hunt
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It was back in 2019 that Bontrager unveiled its WaveCel technology to the world. Instead of relying only on the typical expanded polystyrene (EPS) construction for impact protection, WaveCel adds a honeycomb-like structure inside the foam. WaveCel is a direct competitor to MIPS, looking to lessen the impact of rotation in a crash (it also works to absorb linear impact forces). The unavoidable issue with WaveCel is that it uses a lot of material, which adds both weight and somewhat compromises ventilation. Are these issues a deal breaker for what is a comfortable and feature-packed helmet? 

At £150 / US$160 / AU$230, the Circuit occupies the upper end of the range of second-tier helmets that I am currently reviewing. The Circuit has been out for a few years now so finding it at a lower price is easily done with a little bit of online shopping. 

The short of it: If you are looking for a commuter or cold weather-friendly helmet the Circuit might be for you but for more general road riding, the compromises forced by the WaveCel construction make other helmets more appealing.

Good stuff: Comfortable, good coverage, Blendr mounting options are a welcome addition.

Bad stuff: WaveCel prevents the stowage of glasses, is heavier than others at this price, and is not aero-optimised or well-ventilated.  

Outer view of Trek Circuit WaveCel

A premium and well-fitting helmet 

Getting the helmet out of the box, the first thing that goes through your mind is that it certainly isn’t the lightest helmet at this price point. Of course, some of this weight can be attributed to the magnetic blendr mount (27 grams) that can be removed (more on that later), but at 313 grams for a size small, it is certainly heftier than many of its rivals. For example, the Van Rysel FCR weighs 253 grams and Kask’s Mojito 3 215 grams. The Circuit scores highly in Virginia Tech’s testing protocol, with a five-star rating. It doesn’t particularly stand out from the crowd, ranking 77th overall, but that said, 149 of the 250 helmets the VT lab has tested get five-star ratings, so it is a crowd.

This is partly attributed to the fact that Trek is the only brand to make WaveCel helmets whereas (with the exception of Kask) substantially all other major helmet manufacturers use MIPS. If the weight of the Circuit is of concern, there are lighter helmets with as good protection at this price point. 

Immediately you can’t help but notice that the Circuit looks and feels remarkably well-built. Part of that is down to its slightly heavier feel in your hands, but it is also well-finished and feels premium. 

The helmet has a slightly more oval shape to it than the likes of Specialized’s Propero 4 and more in line with Van Rysel’s FCR or Kask’s Protone. It is not overly narrow but does sit more snugly on the sides of the head than other options. I personally find that a slightly ovalised helmet is more comfortable for me, with the Van Rysel FCR a stand-out helmet on the comfort front along with KASK’s Mojito3. If you have a more rounded head, finding the right fit with the Circuit might be a little trickier and a more rounded helmet might be the better route.   

Inside Trek Circuit WaveCel

Nothing is groundbreaking about the Circuit’s retention system, but, like other things on this helmet, it is simply done well. A Boa dial takes care of retention, with a simple three-position slider to adjust the height of the cradle. Getting the helmet to fit exactly where I wanted it to was a little bit on the fiddly side, as I found the cradle height adjustment tricky to execute. 

The only real issue I ran into with the fit was around the ears. The junction between the front and rear strap is taken care of by a fairly sizeable plastic Y-piece. The size of this alone is not an issue but I did find that getting the yoke in the right place so that it sat nicely on my cheeks was an arduous task as it is not height-adjustable. I also struggled to get the helmet set up so that both the front and rear straps lay flat on my skin without too much excess. This is something that can become a distraction on high-speed descents when the straps start to buffet around. 

As someone with a small but pronounced irregularity towards the top of my head, it can be difficult to find a helmet that sits comfortably. This can often be a hotspot with some helmets, especially when I have shorter hair. The Circuit sits nicely on my head with a feeling of more coverage than Specialized’s Propero 4, for example, and very similar to Bontrager’s Velocis of a few years ago. The retaining band sits nicely around my brow and then extends around the back of my head sitting low, this provides a really secure fit without the need to run the retention system excessively tight. 

Trek Circuit buckle

The Circuit uses a traditional strap design with a pinch to release the buckle. This is a tried and tested method and although isn’t the magnetic FidLok we are seeing on a number of premium helmets these days, I didn’t find myself wanting that either. 

A small detail for me that can make or break how I feel about a helmet is how well it retains the strap setting. I personally don’t like it when from ride to ride the strap creeps looser and it constantly needs readjusting. I was happy to find that over a few weeks of riding, the strap on the Circuit remained firmly in place. 

The ear splitter

With the helmet on it hides its weight well. It is not especially compact on your head but equally, it is not bulbous or cumbersome. The aesthetic of the helmet when on my head was pleasantly understated, and well proportioned. There is nothing shouty about this helmet’s design, which is something I liked. Internally the single-piece foam pad provides ample coverage for the helmet to feel comfortable across all of the skull. It is also noticeably comfortable around the forehead with the pad not leaving any indentations when you remove the helmet.

Unlike some helmets with MIPS, the Circuit also feels incredibly planted on your head. It is something that a lot of us have grown to ignore with MIPS-equipped helmets, but the system does mean that the outer shell of the helmet can feel a little disconnected from your head, particularly on rougher stretches of road. With WaveCel the helmet’s outer shell is fixed which is a pleasant feeling on some of the rougher sections of tarmac around the southwest of England. 

Magnetic helmet mounts are a win

Let’s talk about that magnetic Blendr mount. On the helmet, the most likely use of this is to fit a light but it can also accommodate an action camera if you so desire. What is nice about this system is that it can be installed and removed on the fly.

Rear of helmet with lights fitted

I have found this feature particularly useful with a GoPro as I can keep the camera in my pocket until a video opportunity presents itself. Then it is simply a case of bringing the mount in the vicinity of the magnet in the helmet and you are good to start recording. It also has the added benefit that in the event of a crash anything mounted to your helmet will naturally be released allowing for the helmet to do its job unhindered by a light or camera. It is not necessarily the first benefit of the magnetic Blendr mount, but it is certainly one that is notable. 

Along with the magnetic Blendr mount, there is also a rear light mounting point integrated into the back of the helmet. This is arguably more useful to a broader range of riders as it offers a sleek, neat and convenient solution for mounting a light to the rear of a helmet. This does mean finding a Blendr-compatible rear light with Bontrager’s Flare RT a natural companion for the helmet. At 40 grams and offering up to 90 lumens it packs a punch without adding too much bulk to the helmet. 

The helmet worn with the lights mounted

There is certainly a benefit to mounting lights to a helmet in comparison to on the bike. The higher position is easier for motorists to see. As you move your head this irregular movement pattern also helps draw attention to the lights in a way that a bar or seatpost-mounted light cannot. (The drawback to helmet-mounted lights is that brightness relies partly on lens design and if your head is not perfectly angled to direct the light straight back, it may seem less bright to motorists.)

With the Bontrager Ion Comp R front light and Flare R rear light fitted the helmet does become a little top-heavy. The magnetic front mount is a joy to use and incredibly easy to install and remove the light without needing to remove the helmet. It is also incredibly secure with no amount of heavy metal head banging able to get the unit to shift. 

The rear light is a little fiddlier to fit with the helmet on. The light slides onto the mount in a sideways motion but it is fairly easy to miss one of the rails and have the light tumble off back into your hand. Once in place it it held firm but it would be nice to see the rear light get the same magnetic treatment as the front. 

The rear of the helmet with the light removed

The additional features are a welcome inclusion as they make the helmet a versatile and easy option to live with. For riders who commute, the ease of mounting lights is a real benefit, especially for winter riding and commuting. That puts the Circuit above the others at this price point at least in this aspect. However, it is not all sunshine and rainbows with the Circuit having a few shortcomings that are hard to ignore. 

It’s hot even by British autumn standards 

Having tested this helmet in British autumn with the average temperature sitting around 8-15ºC, I have found the Circuit to be noticeably warmer than other helmets I have tested over the same period. In autumn and winter, this is certainly not a bad thing. Heading out for an early morning weekend ride before the day has managed to wrestle its grasp of the temperature has been pleasant with the Circuit. 

The nature of the WaveCel construction means that the vents are not fully open and airflow is somewhat restricted through the helmet. At this time of year, it isn’t something of concern, however I can already tell on a few occasions when the temperature has crept up into the high teens that there is noticeably less airflow than in other helmets. In hotter climates, that will be disappointing given the size and number of vents present. I would say it has a similar cooling quality as an aero helmet without boasting any of the watt-saving design cues. 

WaveCel is fairly restrictive when it comes to ventilation

Considering the helmet is of a more traditional ventilated design and is deficient in any aero-design inspiration it is hard to not find yourself looking to either a better-ventilated or more aerodynamic helmet. Specialized’s Propero 4 is a full-on aero lid that has a lot of shared DNA with the S-Works Evade 3 however even with these outright aero credentials, I did find that there was a more noticeable through flow of air than with the Cirucit. 

The WaveCel construction leads to my other affliction with the Circuit. As a rider who finds himself at the sweatier end of the spectrum, it is likely that throughout a ride I will want to remove my glasses on a climb to prevent sweat from rendering the lenses all but useless. Firstly, the Circuit does do a better job than most at channelling the sweat built up away from the brow. The result has been that I have had fewer issues with sweat dripping onto the inside of my glasses which I have been very grateful for. 

Inside the helmet

This, however, doesn’t negate my need to stash my glasses throughout a ride. Typically given the choice I like to put my glasses in the vents above my forehead. It’s easy, and convenient, and keeps them from getting dirty and sweaty. But the honeycomb-like construction of WaveCel makes placing glasses in any vents impossible. This is far from ideal as it leaves few options for suitable places to store my glasses. In the past with helmets that lack the ability to hold glasses, I have found that placing them on the back of my head is the next best solution however, multiple times when descending I found that the rushing air would begin to pull my glasses from where they were kept. 

Glasses were difficult to securely stow

Would I buy this? 

Overall testing in British autumn I found the Circuit to be a good option for a cold weather and commuter helmet. For my ovalish head shape its fit is up there with the best on the market and it is nice to see the additional features on the helmet that make it a little more versatile.

Still, it’s hard to overlook some of the Circuit’s glaring flaws for general riding. WaveCel is yet to win me over from MIPS due to the weight penalty, cooling, and limitations around glass stowage. Although I didn’t get to test the helmet in any hot conditions, the WaveCel construction undoubtedly restricts airflow with the Circuit being noticeably warmer than other helmets at this price point that I am currently reviewing.

As a result, I think the Circuit is best suited as a helmet for a cyclist who is looking for one helmet for commuting and enjoying a cafe ride through the colder months. The ease of mounting lights to the helmet is to be commended with the magnetic Blendr mount an effective solution for mounting a front-facing light. 

The lack of aero optimisation may detract from the helmet’s appeal for some riders. That’s certainly a factor for me, but more importantly, the inability to stow glasses, the weight penalty, and poor cooling all combine to make this helmet far from my first choice.

Keep an eye out for more reviews of more brand’s second-tier helmet offerings in the coming weeks and months. Let us know if there are any helmets you are desperate for us to test in the comments section. 

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