When it comes to wheels, bike companies are rarely seen as providing the top-of-the-line product. While Giant, Felt, Specialized, and Trek all manufacture wheels, when it comes time to pick up a new set, athletes typically looking to the standard wheel companies like Zipp, Reynolds, Enve, and the like. And honestly, that’s a shame, because there are some great products out there. We previously covered the Bontrager (Trek’s internal component company) Aeolus 3 D3 Clinchers and Aeolus 9 TLR D3 Clincher. We liked them so much that there may be a set hanging around the AeroGeeks garage for … “testing” purposes. Bontrager not only stands its ground against the purpose build wheel manufacturers, they also actively compare themselves to the competition. Which is why we’re pretty excited to be checking out their newest wheels – the Aerolus XXX line.
The Bontrager Aeolus XXX
Lighter, faster, more stable, and better braking. That was the mission statement for Bontrager when crafting the Aeolus line. Basically, they wanted to better just about every criteria we think of when testing a wheel. This also meant that the status quo had to go. This would be a new line of wheels from the ground up. Bontrager captured the entire development process in the white paper you can download here, but first, let’s cover the highlights.
Development started not with the wheel design, but by better understanding the conditions the wheel would find. As an aside, FLO did something similar with their latest wheel sets. Bontrager performed a detailed research study on wheel aerodynamic stability. They started by comparing actual ride wind speed and yaw data with rider feedback indicating feelings of instability. Bontrager set up a Madone with a wind speed and yaw measurement sensor and tested different wheels on a windy day. When the test rider felt unstable, they flagged the data to determine what caused the instability. This allowed them to identify riding conditions that can make a wheel feel unstable.
Now came the actual design process. Aeolus XXX are optimized around 25c tires for aerodynamics and have an inner width of 21mm for a great ride and tire support with larger-than-traditional road tires. Rim width development started by creating a CAD model to mimic all reasonable rim shapes and a 25c clincher tire model that would properly change shape with each varying rim width.
After narrowing in on final shapes, the Trek prototype group machined three solid prototypes per model for wind tunnel validation. These shapes were chosen from a small zone on the optimal pareto front for drag/stability and had relatively similar shape.
Since late 2013, Trek has been using Walter H Beech Tunnel at National Institute of Aviation Research (NIAR, http://www.niar.wichita.edu/), located on the campus of Wichita State University. To make the tunnel bicycle-testing compatible, Trek has successfully built and installed a proprietary bicycle mount with an internal motor that drives the motions of bike wheels.
Trek follows a strict tunnel testing protocol. To document the tunnel’s operating condition on test day, WSU created an aluminum disk that is tested at the beginning of each test day as a calibration device. The results from the calibration disc also are used to validate variation in measurements for tests that are months apart.
For wheel-only testing, the test wheel (front) is mounted on the bike mount’s rear struts. For a typical wheel test, the inlet air speed is set to 30mph, and dynamics pressure (q =1/2 rho v^2) is held constant throughout the test.
Stopping was another critical element that Bontrager wanted to nail with the Aeolus XXX. When we previously reviewed the Aeolus 9 TLR we said “Braking was our one major issue with these wheels. Braking with the included cork pads just wasn’t up to some of the recent options from Zipp and Reynolds – and that was in the dry.”
For Aeolus XXX, Bontrager developed a brake track to provide exceptional rim brake performance in both wet and dry conditions. They invested in an automated laser machining center that roughens the brake track to an optimized level that maximizes braking performance when used with Black Prince pads. They call this technology Laser Control Track. Field testing comparing Laser Control Track braking performance to the top competitors determined that the Laser Control Track was quieter, had better modulation, braking performance and gave a better sense of control than the competition.
The Aeolus XXX hoops are matched to DT-Swiss hub internals with 36-point star ratchets laced with DT-Swiss Aerolite spokes. The graphics are laser-etched to provide a clean finish without additional weight. Like the Aeolus TLR that came first, the Aeolus XXX is 100% tubeless ready. All Aeolus XXX wheels are designed and domestically manufactured at Trek’s Global Headquarters in Waterloo, WI, USA.
The Options
Aeolus XXX is available in three rim depths for rim and disc brakes. All available in tubular and clincher versions. The Aeolus XXX 2 with a 28mm depth is the lightweight climber, strong enough for cyclocross and gravel riding and retails for $2399.98 as a set. The Aeolus XXX 4 with a 47mm depth is the do-it-all workhorse, fast and stable for everyday aero performance, $2399.98. And the Aeolus XXX 6 with a 60mm depth offers ultimate speed with unmatched stability, bringing an ultra-aero wheel to more riders and conditions, $2399.98. As AeroGeeks, lets dive into the Aeolus XXX 6 a bit.
Bontrager tells us that the Aeolus XXX 6 is lightning fast yet has great aerodynamic stability. If you compare Aeolus XXX 6 to prior Aeolus D3 TLR wheels, they have the speed of 70mm depth Aeolus 7s but handle like the 50mm depth Aeolus 5s. They provided us with a detailed comparison of their base specifications versus the Zipp 404 NSW and Enve 6.7.
What really stands out to us is the massive 28mm width – which we believe is a results of concentrating on 25mm tires versus 23m.
Next is the aero data. Again, Bontrager compared themselves against the Zipp and Enve wheels. (The one thing we aren’t 100% sure on is if the yaw degrees on the bottom chart are also for the top chart but we believe they are).
Bontrager also shared wheel on versus wheel off testing using a Madone as the bike of choice.
Our Thoughts
Well, to start with, this first look is a literal first look. A week or so ago we received a set of Aeolus XXX 6. Unfortunately, we have been extremely limited in ride time, so we are not yet ready to call this a review. Instead, we can cover a few highlights.
To start, the wheels look simply fantastic. The laser etched graphics and brake track are head turners. These are going to turn heads at the coffee shop, in transition, or at the start line of your local gran fondo. But of course, you aren’t still reading this to find out how they look, are you?
At 60mm these are a bit shallower than the wheels we typically test and as a result we know they are going to be a touch more stable. So far, they have gone beyond expectations. The winds of South Florida have not been too kind lately, but so far so good.
As for braking, similarly, we have been limited and everything has been in the dry lately. But these are a definite step (or three) from the previous iteration. They are much more predictable in their stopping abilities. We suspect part of this is the switch from cork to proper Black Prince pads. But the bite of the laser etching is noticeable as well.
We had a small challenge getting the tires mounted. With tubeless ready wheels we find that the wheels are built to have a very tight seal with the tire. And these seem to be no exception. The good news was our trusty Conti GP 4000 II had no issues being installed, but we did struggle with some other options.
Our big question beyond what we will find out in our long-term review is really where is the Aeolus XXX 8/9? We would love to see this shape upsized to a time trial style option.
Wrapping Up
Based on both the whitepaper details and our initial ride time, the Aeolus XXX is shaping up to be a winner. When our biggest issue with their predecessor was their braking – and that is one of the things that Bontrager optimized with this design – we had a hunch that these would be special. And so far, they have not disappointed. Stay tuned as we put some real miles on these wheels to find out if our initial good feelings hang around.