Bontrager today launched the latest range of Aero carbon fiber wheels. Offered in depths of 51, 62 and 75 mm, most of the claims and features are about what you would expect. They are more aerodynamically efficient, more stable in crosswinds and wider than before. However, all three new wheels are not only discs, but also clinker, including for the professional teams sponsored by Trek and Bontrager, which are supposed to use them from the beginning of this season.
In other words, there is no tubular. No brakes on the rim.
The latest frontier in air wheel performance
The evolution of air wheels over the years can be summarized in several key stages. First of all, the designers were primarily concerned with shapes that were fast in a straight line, leading to all sorts of nominal V-shaped rims. Then, cross-wind speed became a bigger business, which attenuated all those shapes, making cross-sections look more like a U than a V. When engineers put more emphasis on cross-wind stability, those U-shapes became rounder and also fatter overall.
Tire beds have continued to grow in size – albeit continuously smaller relative to the outer width of the rim – as designers now look more at running efficiency as a way to achieve higher speeds.
The latest shapes of the Bontrager rim have been developed with the help of new and fancy computers from Trek HQ, which not only run 3D fluid dynamics simulations, but actively help engineers adjust the shapes to achieve the desired characteristics. So yes, Bontrager actually says that while significant traction improvements are getting harder and harder to get from modern airline wheels, there are still some juices out there.
Aero matters aside, however, what will probably be more visible to everyday riders is the wider width of the inner rim. The three newest Aeolus aero wheels from Bontrager have very generous outer widths of 31 mm, matching the inner ones of 23 mm, both of which are supposed to be optimized for tires with a width of 25 mm (printed width, which would throw up to about 27 mm wide a rubber bed). In this configuration, Bontrager claims some “off-graph” gains in terms of both efficiency and stability.
Things get more interesting when you include rolling resistance in the equation. Beds with wider rims have long been seen as a way to improve tire efficiency, given their wider shape, increased air volume and lower operating pressures, but only recently have wheel brands incorporated this aspect so deliberately. in design toolboxes.
When both aerodynamics and rolling resistance (including the transition from tubular to tubeless clinchers) are taken into account, the simulated numbers become quite interesting. Bontrager says a front-end platoon rider traveling at approximately 45 km / h (28 mph) will save 6.3 watts of effort when using a tubeless Aeolus RSL 51 instead of a tube-equipped Aeolus XXX 4 (disc brake for both). And in a 1,500-watt sprint – where aerodynamic gains would be increased – Bontrager demands a total saving of 34 W when using the new Aeolus RSL 62 with tubeless tires instead of the tubular Aeolus XXX 6.
Speaking of racing, Bontrager says Trek-Segafredo riders have used the new wheels this season, including tubeless tires from Pirelli’s sponsor. In fact, Bontrager says Jasper Stuyven started on the front wheel Aeolus RSL 75 and Aeolus RSL 62 in his Milan-San Remo victory (moving only to an older XXX tubular after a puncture due to the alleged limited supply of wheels us at the moment).
By the way, the tubular and brake wheels on the rim are not completely dead at Bontrager, although they are clearly on the life support.
“We will continue to have rim braking options for transportable wheels and, in fact, the Pro 5 wheel brake is one of the best-selling wheels,” said Alex Applegate, Bontrager’s marketing manager. “As for the tubular, we will continue to have the Aeolus RSL 37 offered in a tubular. 37 has a narrower profile, is more optimized for lightweight climbers and makes more sense for tubular applications. That wheel will remain in line. ”
Model details, prices and availability
In addition to the inner and outer rim widths, the three Aeolus RSL TLR wheel models – RSL 51, RSL 62 and RSL 75 – share the same stainless steel spokes with DT Swiss Aerolite blade (with 24 front and rear holes) , Externally located DT Nipples Swiss Pro Lock and low-profile Bontrager cartridge bearing Center Lock disc brake hubs, which combine features from the DT Swiss 240 and 180 hubs and use the company’s latest Ratchet EXP steering mechanism.
The claimed weights for the three depths are 1,410 g, 1,520 g and 1,645 g per set, all with a retail price of USD 2,400 / USD 3,800 / GBP 2,000 / EUR 2,400. The wheels will be sold individually if the riders want to organize a staggered configuration and none of the wheels has any weight limit of the rider.
For trips with more reasonable budgets, Bontrager also offers the Aeolus Pro 51 TLR disc, which uses the same rim shape as the Aeolus RSL 51, but with a less expensive level of carbon fiber, the same spokes and spheres and hubs Bontrager similar. based on the 350 model of the DT Swiss mid-range. The retail price is 1,300 USD / 2,200 USD / 1,300 GBP / 1,300 EUR, and the claimed weight is 1,590 g per set.
One thing to keep in mind regarding tire compatibility and claimed weights is that Bontrager cites those tubeless figures, including molded semi-rigid plastic rim strips that provide the inner seal and bead locking capabilities needed to maintain the entire sealed system. Each of these rim strips weighs 60 g, but since they are not needed to run tubes, the actual weight is actually a little lighter. Bontrager also offers a ready-to-use tubeless tape system that still retains air tightness while saving about 100 g.
We launched the Aeolus RSL 51s here for review, and the actual weight is only 650 g for the front wheel and 770 g for the rear, for a total of 1,420 g without rim strips – a really impressive figure for carbon discs compatible with discs, this depth from a mass brand.
Looks like we’re in the “fourth winter” here in Colorado, but hopefully this is the last round before spring comes seriously, so I can finally get to that. Stay tuned for a more in-depth review soon.
For more information, visit www.bontrager.com.