Bontrager Aeolus XXX 6 – Review

It’s been just over a year since we first shared Bontrager’s Aelous XXX lineup with you. We had just had them for a few days when we shared our First Look, but we said “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.” But that was a year ago and since then we have had plenty of time to put real miles on the wheels and find out how these stacked up. So, did they live up to our expectations or let us down? Well before we dive in let’s do a quick recap.

The Bontrager Aeolus XXX 6

Bontrager is Trek’s in-house component company. But don’t be mistaken thinking that this means Bontrager is just making low cost – generic products. Quite the opposite in fact. Bontrager is one of the most underrated component manufacturers out there. We previously covered the Aeolus 3 D3 Clinchers and Aeolus 9 TLR D3 Clincher. We liked them so much that there has been a set hanging around the AeroGeeks garage for … “testing” purposes. Bontrager not only stands its ground against the purpose built wheel manufacturers, they also actively compare themselves to the competition.

Development of the Aeolus XXX line 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 captured the entire development process in the white paper you can download here.) 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.

The entire Aeolus XXX line is 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.

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. Their 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 Aeolus XXX line 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 (the ones we have been riding with) that offers their top end speed, bringing an ultra-aero wheel to more riders and conditions, is $2399.98.

The Aero Data

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.

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

As fans of the previous generation Aeolus wheels, we really were looking forward to some extended ride time with the Aeolus XXX 6. Our one hesitation coming into this review however was the rim depth – at 60mm this was quite a bit shallower than the 80-90mm wheels we spend the majority of our time on. So, our analysis of cross wind stability was a bit skewed (it’s not easy or fair to compare an 80/80 setup with a 60/60 setup). So, acknowledging this, we still want to call out just how stable these wheels were. Even in an inconsistent wind – the wheels tended to ride consistently. You don’t get that harsh on\off feeling that some wheels (even a 60mm wheels from a generation or two ago) can sometimes give.

Flat out speed is something that is equally unfair to compare between wheels of varying depths, but we are going to try. Bontrager’s data (which we always will be somewhat wary of any manufacturers data) suggests these are world class – and our measured ride times do support this. We wish we had gotten these in the available disc brake configuration so that we could have swapped them onto one of our road bikes with similarly deep wheels to better quantify the speed. But even so, anytime you show up on a ride with the shallowest wheels in the group and you feel no additional effort to match the group speeds – it says something about the wheels.

Braking was the area we were looking for the strongest improvement compared to the original Aeolus wheels. 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.” The Aeolus XXX6 however was more than up to the task. We felt these wheels were on par with or better than the majority of carbon wheels on the road today in the dry and even more so in the wet. (Though the manufacturers that that have gone with a heavily dimpled or grooved surface are still king of the rim braking surfaces.) Braking was consistent with a natural catch feeling (no pulsing or grabbing) where you can easily modulate the brakes to your specific needs.

Wrapping Up

So, did they live up to our expectations? The improvement in the braking alone was enough to make that an unqualified yes. Add to that the improved crosswind stability and the Aeolus XXX 6 is a definite winner. Which brings us to our biggest disappointment with the Aeolus XXX line – where is the Aeolus XXX 8/9? The Aeolus XXX line are Bontrager’s fastest wheels and there is nothing for the time trialist \ triathlete. When our biggest disappointment is that there is no wheel for our primary discipline, we will admit it shows that we really like these wheels. But unfortunately, it also means that we will reserve the Aeolus XXX for our road bikes for now and keep crossing our fingers for a deep triathlete specific version in the future.

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