Can deep wheels be fast and not sketchy in high winds? Bontrager engineers set out to achieve a low-drag, low-side-force aero wheel, and have largely achieved that in the new Bontrager Aeolus XXX 6.
The 60mm rim is super-wide at the brake track — 28mm, in fact — but tapers down to more of a pointed rim bed than other stable-in-crosswind aero wheels like the Zipp NSW that have snub-nosed spoke beds.
Bontrager also added a new laser-etched brake track for the Aeolus XXX line, which also has less deep rim versions in the 2 (28mm) and 4 (47mm), as well as disc-brake and tubular options for all rim heights.
Side pressure, but without the sudden jerks
After riding the wheels on a number of blustery Colorado days, I can say the wheels handle calmly for such deep aero hoops. On days with 20-30mph steady winds and higher gusts, I didn't feel like the wheels were dangerous.
Make no mistake, you can certainly feel the wind pressure on the wheels pushing you sideways, but there were no sudden changes in pressure yanking the front wheel.
The XXX 6 felt similar to the Zipp 404 NSW, which I've been riding for months. Is either better than the other at handling crosswinds? I have no idea, but both are leaps and bounds ahead of early aero wheels that were designed strictly for drag reduction.
You can read about Bontrager's detailed efforts and minimizing side force in the wheel's design here.
Great lateral stiffness and low weight
I did most of my testing on an older ( 2012) Specialized S-Works Tarmac. Clearance for the fat wheels was minimal, maybe 3-4 millimeters between the brake track and the inside of the chainstays. Now, I would not recommend you buying these wheels if your bike has similar clearance, but the old Tarmac proved a great tool for testing lateral stability on the wheels.
As a heavier rider (185lb /84kg), I could only get the wheels to touch the chainstays when doing an all-out uphill effort. Under normal riding circumstance, even when climbing slowly out of the saddle, the wheels did not touch the stays.
Again - this setup is not recommended, but it did showcase how tightly the wheels track.
Further, the wheels don't feel vertically like 60mm carbon wheels, which are usually pretty harsh. Thin spokes have more give than rigid carbon rims, and, typically, the taller the rim (and thus the shorter the spokes), the harsher the ride. Now, you won't mistake these wheels for box-rim hoops, but they are noticeably more forgiving than your standard deep aero wheel.
At 1,530g, the wheels wind up nicely. The DT Swiss internals with a 36-point star-ratchet system engages quickly. I did a fair amount of climbing on the XXX 6s, and didn't feel like the wheels were anything close to a detriment. Of course, a shallower rim would be lighter, but the 500g rims aren't exactly boat anchors for a 60mm depth.
Braking - quiet, better than previously, but still a carbon surface
The new laser-etched brake track adds a bit of traction for the SwissStop Black Prince pads. Compared to ENVE's dimpled surface or Zipp's grooved track, the Bontrager surface is much more subtle, and the brake's bite is similarly muted. That to say, braking is stronger than on flat carbon, but not as powerful as ENVE or Zipp's system.
Another difference against Zipp and ENVE - the Bontragers are much more quiet. ENVE and Zipp's textured tracks can make a bit of a video game noise when slowing. The Bontragers are nearly silent.
Besides there being no squealing or humming, there is also no grabbing, pulsing or fading in the braking on descents.
Testing with Shimano's excellent Dura-Ace 9100 calipers, I was able to one-finger brake down sharp and steep descents. You won't mistake the setup for discs, of course, but it's good for carbon.
Testing with the Trek Madone aero brakes, the wheel and pads' braking is less impressive, but that is more to do with the reduced leverage on the aero brakes.
More speed at speed
Of course, the primary point of aero wheels is the aerodynamic benefit - the reduced drag at speed. The faster you go, the greater a factor aerodynamic resistance becomes. And, thus, the less drag, the better.
Here, Bontrager claims it matches or beats ENVE or Zipp at all yaw angles from zero up to 15%, but then give up a little to its competitors at more extreme yaw angles.
From just riding, I can't tell a difference between the three in terms of drag; they all feel fast to me.
One clear difference from Bontrager and the ENVEs I rode is the solid quick release; on ENVEs last year I yanked the rear wheel out of the dropout a couple of times on very steep climbs when trying to respond to attacks. ENVE has since changed its QR design, but Bontager never needed to - its solid, internal-cam design with a sturdy lever is rock solid.
Summary - Nothing out there markedly better
After a month or so of riding, the Bontrager Aeolus XXX 6 wheels appear to live up to their billing as a fast, stable carbon clincher. On windy days the wheels have a noticeable side pressure like any tall-rimmed set, but there isn't any sudden jerkiness.
Similarly, for such a deep wheel, the comfort is fairly good. While some engineering certainly went into the layup for this, the extra girth the 21mm internal-rim width allows for clinchers can't hurt, either.
For me, ride feel is right on par with the latest hoops from ENVE and Zipp in terms of acceleration and handling. Stability in crosswinds is much harder to pin down, but it is noticeable on these wheels. Is it better or worse than ENVE or Zipp? I don't know.
The braking is not as strong as with the textured tracks of Zipp or ENVE, but it is much quieter than both. So pick your poison there.
While I have experienced and seen carbon clinchers from many brands delaminate over the years, I have never seen a problem with Bontrager for braking heat. Further, the company claims it has only had two failures in more than 100,000 wheels, and both of those were minor, with only slight deformation, not a blowout. All that to say, I have confidence in Bontrager's construction.
Bottom line: I would happily race or ride these any day, especially when using Shimano's excellent 9100 calipers.
Are the Bontrager Aeolus XXX 6 the absolute best for the 60mm category? Possibly. I can say I haven’t ridden anything markedly better.
