Review: Bontrager Aeolus Pro 37V TLR Wheelset

Carbon fiber everything has been the pinnacle of high-performance bicycles and components for over 20 years. Just updating an alloy wheelset to carbon makes an immediate difference in ride feel, spin-up and comfort. For the most part, carbon wheelsets (like most carbon bits) are hand-laid and finished — resulting in excess materials and carbon dust. Kicking that process to the curb, Bontrager has partnered with CSS Composites to deliver their Aeolus Pro 37V and 49V road/gravel wheelsets, promising more sustainable and durable wheelsets now and into the future.

Bontrager Aeolus Pro 37V Wheelset Features:

• Versatile wheelset for road or gravel use
• OCLV Next thermoplastic carbon fiber material from CSS Composites
• 37mm depth and 25mm inner width for a a do-it-all setup
• Permanent logos integrated into the molding process
• Tubeless-ready (TLR) out of the box with rim tape and optional TLR rim strips
• Centerlock rotor compatibility
• DT Swiss Aerolite14, 17 spokes and Prolock alloy nipples
• Handmade in the USA with global components
• No rider weight limits
• Hooked bead for added tire security and compatibility
• Optional TLR rim strips add 65 grams and cost $20.99 each
• Max tire pressure: 28c – 90psi | 32c – 70psi | 40c – 50psi
• Weight: 850 grams (rear) and 680 grams (front) — 1530 grams complete
• MSRP: $1799.98 (XDR Driver $99)

Thermo-whatchamacallit?

Those unfamiliar with the typical carbon fiber layup process may not understand that almost every carbon fiber bike component is hand-laid into a mold using a “layup schedule.” This recipe dictates the placement of each layer of prepreg carbon to not only make the eventual shape of the item, but to also optimize stiffness, reduce weight or improve durability. Once all the pieces are methodically placed in the mold, it’s baked under high temperatures and pressure to eliminate air pockets, permanently adhere all layers together and make the sleek and smooth carbon fiber shapes we’re all used to. As you can imagine, it’s a labor-intensive process that’s reflected in the price of carbon fiber bike parts. And, once set in place, there’s no undo button, plus all waste isn’t reusable.

Enter CSS Composites, who has been grilling up custom-tuned termoplastic carbon rims since 2018 (on top of their decades of experience in the aerospace industry). Instead of traditional pre-preg carbon fiber sheets, CSS utilizes rolls of Toray nylon/carbon that is precisely cut by machines and tacked into place ahead of final shaping and finishing. Any waste can be repurposed and the raw materials don’t require as much care as storing single-use pre-preg carbon. CSS calls their material FusionFiber, but Bontrager calls it OCLV Next and the process combines the most advanced automation with skilled technicians to ultimately deliver the Bontrager Aeolus Pro 37V and 49V wheelsets. CSS’s operation, isn’t a one-size-fits-all kind of thing either — every brand partner can work with them to determine the shapes, specs and wall thicknesses to optimize the performance and ride characteristics of each wheelset using proprietary molds.  The Team at GCN toured the factory in Gunnison, UT (about 1.5 hours south of me) and delivered an inside look at the whole process.

Trek, Revel Bikes, Chris King and other brands are partnering with CSS to deliver a variety of unique wheelsets using their FusionFiber technology. Will it be the future of carbon fiber manufacturing? For some applications, it certainly could be.

Initial setup was… less than ideal

In addition to the unique construction process, to me, the specs of the new Aeolus Pro 37V are fantastic in every regard. Durability and ride quality are paramount, and the weight is definitely respectable, but not class-leading (especially if you opt for the TLR rim strips, like me). But, before getting too far downstream, let’s cover tubeless setup.

Initially, my goal was to test the road characteristics of the Pro 37V wheelset. They arrived tubeless-ready with standard tape — a departure from Bontrager’s typical TLR rim strips. Without the strips, the wheels are 1530 grams, but I had mixed results seating tires with that setup. Trek states that the minimum tire width is 28c, and I dutifully tried and failed miserably to seat a pair of Bontrager R3 Hard-Case Lite TLR 28c tires using the Bontrager TLR Flash Charger pump. Hmmm. Determined to make the 28c tires work, I went to my local shop to see if they could get them seated. The result? More frustration as I walked out the same way I entered — with a pair of unmounted 28c tires. 32mm tires were possible, but the 28mm’s had my number. I typically ride with 30mm+ tires anyway, but you’re on your own with smaller tires.

To further improve tubeless setup, I installed TLR rim strips, which finally made it possible to set up 28c tires. Not only was it easier to set up, I actually don’t mind the added weight of the rim strips since I’m changing tires out so often. But, if you can get your preferred tires mounted up without those strips, you’ll enjoy the lightest setup possible (1530 grams vs 1660 grams).

After wrapping up tarmac testing, I installed the Bontrager GR2 Team Issue tires and, even with the rim strips, they were pesky. With some patience and maybe a little luck, I was able to seat them and they have been fantastic since. A compressor and high-flow valves, like the Reserve Fillmore valves will all help.

You’ll be at ease knowing that maximum allowed tubeless tire pressures are well above what you would ever inflate them to. So, rest easy with the 37V’s — you won’t come close to maxing them out if you feel the need to ride higher pressures (even though you shouldn’t). At my 175 lb. rider weight, I’m running between 55-60 psi. with 32c tires and 36-38 psi. with 40c gravel tires.

Rocking the tarmac

Hot on the heels of my time with the ultra-fast and light Zipp 353 NSW wheels, I dove headlong into the 37V’s. Admittedly, it’s an unfair comparison, but still these wheels have a lot going for them. As mentioned, the 37V’s are not going to compete well in a “gram-counter challenge.” They are respectable and do tip the scales on par with the Zipp 303S. Out on the open road, they do spin up well and test out among the better wheelsets I’ve ridden in my standard roll-to-stop testing.

If you’ve perused the interwebs for carbon wheelset failures, you’ve likely seen some pretty scary images. With thousands of miles under my belt on carbon wheelsets, I haven’t had a single issue (knocks wood). Disc brakes have further reduced the chances of failure due to removing braking heat and friction from the sidewalls. I’m also convinced that modern carbon wheelsets from major brands are more durable and reliable than ever. Further adding to my confidence, OCLV Next boasts no rider weight limits with a lifetime warranty to the original owner. Honestly, very few wheelsets are backed up so well. Knowing that, any carbon concerns are put to rest.

The shape of the 37V’s screams versatility — both to cheat the wind and also spin up and climb well. 37mm depth isn’t all that deep by today’s standards, but it certainly doesn’t drag you down. Aerodynamics are good, but you won’t unlock any cheat codes like you would with the deeper 49V model or, some of my favorite Aeolus Pro 51’s. I feel like the depth is great for all-round road use.

Once rolling, the ride characteristics of the long-chain OCLV Next thermofibers come into play. It didn’t take me more than a few pedal strokes to notice the isolation they provide. Small road chatter and imperfections are either muted or reduced in a noticeable way. On the flip side, that vibration reduction does result in a little less lively, playful feel to them. Over the course of a long ride, that reduction in micro-vibrations allows my body to feel more relaxed and comfortable compared to a more taut-riding wheelset (like the Elitewheels Drive G45). In spite of that, I’d be lying if I told you I didn’t miss the pop of livelier wheelset. But, truthfully, my 49-yr-old lower back really appreciated the cool, calm and collected ride of the 37V’s. I’ll take that as a win. 

Regarding the comfort of these wheels, Trek has stated:

“Tested on Paris-Roubaix’s roughest cobbles, the new Aeolus Pro 37V wheels provide 15% more radial deflection and reduce vibrations by 5% while being over 100g lighter than the previous Aeolus Pro 3Vs.”

Lateral stiffness and handling on mountain descents are excellent and so is stability aboard the Ari Veyo SL they were tested on. It’s interesting just how much small variations in rim shape can make or break stability. In all my miles, I’ve had zero stability issues in strong crosswinds. If you live in a windy location, these are a great wheelset. In the end, my climbing and rolling segment times are within spitting distance of my best times. So, all that smoothness isn’t slowing things down when the stopwatch is the authority.

The Aeolus Pro 37V’s are made for gravel

While I did enjoy these wheels on the road, where they really shine is on the gravel. That 25mm internal width does wonders for tire shape, comfort and performance. 40c tires will measure out to 42c and that added volume can be felt. Once configured, I dropped them on the Open WIDE gravel bike and never looked back — venturing into mixed-condition rides with absolute confidence.

As mentioned, the long-chain polymers used to make OCLV Next not only smooths out pavement, but it also significantly quiets gravel terrain. After just a few hundred feet of gravel, I was once again smitten by the smoothness these deliver. On the smoother gravel tracks, they feel fast and confident. And, on more burly terrain, I couldn’t even get them to bat an eye. Take, for example, this mixed-gravel route that I ride regularly. It consists of road climbs, rolling gravel and technical singletrack. The harder I pushed them the more they responded without missing a beat. Bonkers.

After putting them through their paces on all the local routes, I’m sold on the quiet demeanor of these wheels on top of the durability they provide. Looking them over with a keen eye, I can’t find any signs of wear. And, the baked-in logos will never peel off or get scratched.

Testing has continued into warmer weather, with trips to Southern Utah as well. I have had several square-edged impacts that compressed the tire to the rim with a thud that hurts your soul. I’m happy to report that no rim damage has happened and the 37V’s remain true and undamaged.

After riding a number of Bontrager wheelsets, I remain impressed with their hubs and the Rapid Drive 108’s used here are no exception. They spin up fast, roll along nicely and offer excellent engagement. I didn’t think much about their engagement speed and that’s a good thing. Truthfully, they feel on par or better than any hubs in this price range. The overall build quality is outstanding and I do love the quiet performance of the 37V’s and the sustainability of the OCLV Next material.

Review period: I have tested the 37V’s over 500 miles over a period of 7 months as of publishing. Testing will continue and any updates added here over time. 

Buy Now: Available from TrekBikes.com