What's Cool In Road Cycling

Bell Star Pro Aero Helmet Review

Two of the biggest concerns about my buying an aero helmet have been the look, and how well they cool my head – so can staying cool and looking cool co-exist in an aero helmet? Bell says yes, and submit the Star Pro as Exhibit A.


Aero road helmets have in recent years moved surely from novelty to mainstream in the pro peloton. Most, if not all of the major helmet makers now offer their own version of an aero road helmet. The Bell helmet company started in 1954 making motorcycle helmets, and are likely the most well known moto helmet maker in North America. Those many years of developing helmet tech for high-speed moto races has given them an enviable depth of knowledge that’s been used to develop to their cycling helmets.


The basic problem is that a smooth surface is generally considered the best for aerodynamics, but once you start cutting holes for ventilation, it becomes less aerodynamic. More holes equals a cooler head, but also more disruption to the air flowing over your noggin, which in turn creates drag that slows you down.

Add in the essential element that a helmet is first and foremost on your head for protection, the idea to create something to both cover, and not cover becomes a problem that requires a lot more thought and ingenuity than you might think.

Deep from the archives – an ad for the Bell V1-Pro c. 1980.

As a teenage motocross racer, I remember Bell was the only helmet anyone racing would consider buying. A few years later, when I started racing mountain bikes in the early 1980’s and required a helmet (just for the races) – Bell was again the logical (and almost only…) choice – quick show of hands of you owned a V1 Pro? It looked like a cereal bowl, but had a certain “I mean business” look about it that was one of the best tools we had for psyching out opponents on the start line.

While Euro-styled lids became de rigueur in the our Euro-peloton influenced consciousness for some of the past 10-15 years, Bell has in recent years (although never absent from the forefront of the cycling helmet scene) been making a resurgence with more style conscious designs and better technology for both protection, and aerodynamics.


The Bell Star Pro is Bell’s Protour level offering, worn by Team Lotto-Jumbo as proof that it belongs at the top level of cycle sport.

How’s it look?  As you can see – it’s smooth and round – excellent for passing through the air quickly.  There are only 15 vents on the helmet, (low by most road standards today), thirteen of which can be closed off with an on-the-fly closure that’s also designed to smooth airflow even more.

The Star Pro is available with the detachable eye shield in your choice of either a Zeiss or a Transitions lens, intended to be worn in place of glasses. It slots into the browline and stays in place via small magnets. The magnetic field also hold it in place when you want to store the shield at the coffee stop.


The shell is a cageless design made from two layers of foam – each of different densities, to better handle crash management, and allow space for the vent-closing mechanism. The inner layer is a lower density foam to better cushion the head, while the outer layer is a denser version to increase overall impact protection in both low- and high-impact blows.

Another reason there are two halves to the shell is to accomodate the nifty vent closures – they’re handily contained between the two shell layers and disappear from view completely when opened. It’s a slick design that wasn’t the easiest thing to create given the spherical shape of the helmet surface.

It comes in three sizes (Small, medium, and large), a lot of colors including all the standards (white, black, and fluo), and my medium sized tester weighed in at 287 grams without the detachable eye shield.


It’s All About the Airflow
Air flow around the outside of the helmet is part of the big story here, (and what makes this one faster), while airflow inside the helmet is the other part of the story, and what keeps your head cool. Let’s start with the outside…

The shape is a fairly classic teardrop-style, which after many years of being perfected, still looks good, and still works.

This graphic from Bell shows how the Star Pro is faster in both with vents open and closed.

This big plus of the StarPro’s shield is that it ups the aero-quotient by directing airflow around the helmet, and smoothing out the turbulence that comes from the non-aero shape of most faces.  When it comes to going faster, that all makes the most sense, but if you’re wondering why we don’t see more pros wearing the eye-shield in races, you’d best ask their individual eyewear sponsors.

Bell were serious enough about design of this one that they used both the Faster low-speed windtunnel and also built their own wind tunnel in-house so shaping ideas could be tested as quickly as the designers thought ’em up.

The vents on the sides and top to the helmet can be closed with a small slider on the top of the helmet, which smoothes out the airflow even more, making it that much faster.  Testing this one in the winter months, these closed vents were handy in blocking out some of the colder air, and keeping my head a bit warmer.


Airflow around and inside the Star Pro is an impressive part of this helmet. It’s well known that keeping your head cool requires air flowing through the inside the lid, you can still buy helmets that offer nothing more than vents and holes cut into the helmet shell as adequate an cooling mechanism (they’re not.) The active ingredient in keeping your head cool under a protective helmet is that airflow – fresh air somehow getting in, and the hot sweaty air created by your head… getting out.


Air on the Star Pro flows in through 5 large vents cut above the forehead at the browline. They scoop air in and then direct it over the head via deeply cut channels (mine measured from 3/8″ – 1/2″ deep) to exhaust that hot sweaty air out the side and back vents.


Bell calls this “Over Brow Ventilation”, and the air flow and channeling are worth a closer look here too.  The deep channels both direct airflow over your head for ideal movement and venting, and also pull that air out through the exhaust ports.  You can follow the airflow along those green lines above.  Those side and back ports are really exit points for hot air, versus so many other designs who purport that holes anywhere on the head equal better venting and better cooling.  Vents don’t all work in the same way, but Bell’s work exactly as they should… and as you’d want.


Retention is thoroughly modern as well – a continuous loop of plastic encircles the whole head (versus less efficient designs that tighten at the back and cram the helmet back into the forehead).  It’s easily adjustable via a ‘floating’ wheel mechanism that tightens or loosens with a press & spin of the dial.


In making this one as aerodynamic as possible the helmet nerds at Bell also considered how airflow around the chin strap affected this performance. They call it the “Cinchlock strapping adjustor” and it helps keep the helmet strapping flat against the head.


The Star Pro uses a strap system that’s made from slightly thinner material than other helmets. But even more aggressive in cheating the wind is Bell’s left and right under-ear strap adjusters which are visibly smaller and thinner than anything else I’ve seen. The design allows the straps to lay flatter against the head than other designs thereby once again smoothing airflow and reducing turbulence and drag.

As Bell’s Sean Coffey told me: “Strap management was found to make a significant difference….we ran a test with the strapping twisted so that it was facing the wind direction. Keeping the strapping flat against the head saves 9.6 watts @ 50kph. This is why the strap management system on the Star sacrifices a certain degree of adjustability for speed. “

Cyclocross deity Mathieu Van der Poel rode a Star Pro to his 2014 World Cyclocross Championship, and prefers the adaptive ventilation for colder conditions. 

The limitation of the system is a reduced amount of adjustability. Everyone’s head is shaped differently, with ear and chin placements being ever so slightly different as well. It’s why most helmets, including other Bell models allow for both fore and aft, and overall length adjustment of these straps for perfect positioning for everyone. The Star Pro ear straps do allow for some fore & aft placement of the chin strap, but do not allow for any length adjustment – so if your ears don’t fit within the allotted space, you could be in for some irritation or a fit that won’t work at all.

This graphic from Bell shows how the Star Pro’s cooling works vs a bare head, and other helmets.

Strap It On
I’ve been wearing this helmet through the cold days of winter and I like the closeable vents that have helped keep out some rain, and keep in some warmth.  The temperature difference so far has not been really significant versus wearing a decent skull cap under a more traditional style cage helmet, but it’s been enough to notice – and that’s still wearing a skully.

The Cinchlock retention system has proven quite good too – and in spite of my initial concerns about the limited adjustability, it’s fit my head just fine.

Airflow under the helmet is noticeable with the vents open – the deep channels work well and I’d expect this to be a solid performer though most seasons – of course personal preference and perception will be the biggest proof of whether the Star Pro is right for you, but there’s enough well thought out technology here to make it worth considering.

• See more info: Bell Star Pro
   – $280 with shield
   – $320 with Transitions Shield

• Check prices on the Bell Star Pro helmet at Amazon.com.

I’ll leave you with this video from Bell that show a bit of the behind the scenes development on the Star Pro.


Note: If you have other experiences with gear, or something to add, drop us a line. We don’t claim to know everything (we just imply it at times). Give us a pat on the back if you like the reviews, or a slap in the head if you feel the need!

PezCycling News and the author ask that you contact the manufacturers before using any products we test here. Only the manufacturer can provide accurate and complete information on proper use and or installation of products as well as any conditional information or product limits that may limit their use.


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