Khach Me If You Can

New Bike Day is the day that reigns supreme in every cyclists life. Going to pick up a brand new steed will always make any lyrca-clad aficionado giddy with excitement unrivaled by days usually reserved for this kind of glee by the “normal” population. A couple rungs down on stoke ladder is new wheel day. Multiply the typical excitement of a new wheelset with the 6 months I had to wait after ordering the RSLs on the release date in April 2021 and I was rightly salivating when my beautiful new wheelset had arrived. It was finally time to give them a spin.

Race Shop Limited

… or the RSL in the name of the wheelset. Race shop limited essentially means these wheels are tested in world tour settings. Which translates to the most effective marketing pitch to the cycling enthusiast with extra money in their bank account…. The pros use these wheels.

The RSL lineup was introduced as the brands replacement and upgrade to the previous flagship line up released in 2018, the Aeolus XXX.

The RSL wheels come in 4 depth options: 37mm for the climbing specialist, 51mm for the all arounder, 62mm for the sprinters, and 75mm for the time trialist. This greatly oversimplifies the range of the lineup as there are sure to be some overlap and gray areas depending on your specific riding style.

As a heavier/powerful rider who loves to go uphill and also intended to use the wheelset for triathlons, it was more like 50 Shades of Gray, albeit with far less bondage. Luckily the RSL wheelsets boasted improvements in just about every category, including weight and stability, meaning that any tradeoffs in my rim depth selection would be less pronounced.

Aerodynamics

Sorry weight weenies, with the exception of the hilliest routes, reducing aerodynamic drag is more important than reducing weight. This ignores personal preference in how reactive a wheel feels with added rotating weight, that is, how quickly the wheel appears to accelerate when power is stomped into the pedals and a potential to feel lag with heavier wheelsets.

Without going into an in-depth fluid dynamics discussion, the simple rule of thumb is that the deeper the wheel is the more aerodynamic it will be in a straight line. If we ignore all other variables (more on those in a bit) then deeper wheels will be faster by reducing losses due to drag. This is because deeper section wheels allow for more laminar flow around the wheel than shallower wheels by increasing the amount of smooth surface in contact with the air and reducing the length of turbulence-inducing spokes.

Drag force is a square root function of speed. Because of the addition of rotational velocity to forward velocity, the wheels are moving much faster relative to the air than any other part of the bike. This is why the wheelset is one of the best performance boosting upgrades a cyclist can make.

I was previously riding on the Roval CL50 50mm deep carbon wheels. By moving to a 62mm deep wheel I was hoping for some incremental gains in aerodynamics and to use the RSLs as my race wheel while keeping the CL50s for my everyday all-around wheelset.

Weight

The RSL 62s come in at a combined weight of 1520 grams. This is astonishingly light for such a deep wheel. To put it in perspective my 50mm Roval wheelset tips the scales at 1515 grams, meaning for my upgrade there was essentially no weight penalty as a tradeoff to my new aero gains. When comparing the RSL 62s to other wheelsets in the RSL lineups the weight differences are no longer negligible, but in my case it meant I was not likely to notice any acceleration lag or to feel a difference when seeking grades.

When you consider how wide the RSLs are with a 23mm inner width and a 31mm outer width you wonder what kind of carbon magic Bontrager is using to make these wheels.

Stability

Aside from weight, the main tradeoff to the aerodynamic gains of a deeper section wheel are stability, or more specifically crosswind stability. The higher surface area of deep section wheels means the same wind pressure on the surface results in a greater force on the wheel. Assuming you aren’t having a bad day, the last thing you want to happen when descending a mountain at 50 mph is to have a gust blow you across the road (which would then make it a VERY bad day). This effect is magnified with lighter riders that have less inertia on account of their lower mass.

Bontrager has claimed to have mitigated this tradeoff as well through the use of their new 3 dimensional fluid dynamics modeling process which allows them to model the aerodynamic performance of the wheel against all wind angles and conditions.

This also is where the beefy width of the wheel comes into play. A wider wheelset can be more stable, primarily be allowing for wider tires that will boast greater contact area with the ground in additional to lower rolling resistance and a more comfortable ride. I won’t touch the heated rim brake v. disc brake debate that incites so many online forums and cafes, but the additional clearances offered by a disc brake design is what makes a wheel as wide as the RSL 62 possible.

First Impressions

The phone call I had been not-so-patiently waiting for came mid October. My local bike shop had finally received both wheels and they were ready to install.

When I first saw them on my Madone SLR for the first time it was a work of art that rivaled Michelangelo’s Sistine Chapel. I am, admittedly, biased as this is MY work of art, but I stared admiringly for far too long. The wheels themselves are a bit understated as far as high end carbon wheels go, no flashy design or graphics with a discrete carbon weave; however, something about the glossy finish and extra rim depth on my pride and joy simply was the finishing touch to my dream build.

The first thing I did was spin up the rear wheel and let the ultralight DT-Swiss Ratchet free hub go. The deep hum was far lower than any free hub I had heard before. It was loud, yet not noisy. I was elated, this free hub was my new favorite song and I couldn’t wait to play it over and over again out on the road. To any laymen who may have been walking by I’m sure the sound was more akin to a hive of angry baritone bees.

I had tickled 2 of my 5 senses with the looks and sound of my new wheelset. Tasting or smelling the wheels were unlikely to boost my admiration, so it was time to FEEL these things on the road.

Putting the RSL 62s to the Test

I turned onto the road and instantly hammered on the pedals. My Madone spun right up to speed just as she always had, alleviating any lasting fears I had of acceleration lag with my new deeper wheelset. As my speed climbed into the 20s I bent over low in my drops and continued to push watts into the drivetrain. Enthusiasm was surely going to squash any illusions I had of a recovery ride.

The first thing I noticed about the RSLs was the sound. Not the beautiful free hub sound, but the sound the wheels made cutting through the air. Anyone with carbon wheels, or who has been blown past by someone on deep carbon hoops recognized the WHOOSH WHOOSH sound deep wheels make. When ripping a descent at 60 mph a carbon wheelset can leave the impression of a jet flying past… silent until the rider is even with you and then woooooOOOOOOOSH. These produced something entirely different on top of that expected sound. The RSLs produce a mid-high pitch hum when cruising along that reminded me of someone rubbing their finger along the wet rim of a crystal wine glass. The sound was totally unique to me and I absolutely loved it, urging me to keep my speed up to keep the music playing.

The wheels certainly felt fast. At high speeds the RSLs feel like they want you to keep pushing faster, when you let off the power the bike continues to slice through the air feeling like there’s some kind of flywheel effect in play. My average speed seemed to agree with the aero gains of the wheels, but more importantly, my subjective seat-of-the-bibshort meter told me these wheels were the real deal. They felt amazing as if they had breathed a new life into my already punchy Madone.

Before going any further I should add that I opted to run the wheels with tubes and 25C Continental GP 5000 clinchers at 100 psi. The wheels were stiff and with the narrow tires at a high pressure the risk of discomfort from every imperfection in the road could have been high; however my Madone has Trek’s patented Isospeed decoupler system which makes for a much more comfortable ride and likely hid the tradeoffs of my tire and pressure selections.

Leaning into corners at high speeds felt amazing as well and gave me confidence in the handling of the wheelset. No surprise here, I wasn’t expecting any tradeoffs in handling. My main concern would be how the wheels performed in a cross wind with the additional pressure forces.

For the first time I was happy it happened to be a windy ride as this meant I could run the wheels through the full gambit of my elementary tests.

Wind speeds were about 10mph with occasional gusts up to 15-20 mph. The gusts are far more of a concern as you can feel the pressure on the wheel more as the wind suddenly picks up and lets off. With a steady wind the rider’s feedback loop can subconsciously adjust for the side pressure. After initial adjustments are made you can find equilibrium and ride it out.

Alright, let’s cut to the point, I could absolutely feel each gust in the wheels, unfortunately Bontrager had stopped short of working actual magic on the RSLs to overwrite the laws of physics. What was shocking to me was that even with 20% more surface area, the 62mm RSLs felt no worse in the cross wind than my 50mm Roval wheels. All else equal, I should have had 20% more force to wrestle out of my handlebars to stay on the road.

This quelled the initial skepticism I had of Bontrager’s touting of the new 3D modeling process and cross wind performance claims. Just about every new cycling product makes incredible claims that at best need to be taken with a grain of salt. Again my seat-of-the-bibshorts meter was telling me these claims had a sound basis. I was going to have to seriously reconsider my plan to use the 50mm wheels as my everyday set of hoops.

Critiques

I’ve yet to find a perfect product. Despite the awesomeness that come with the RSLs, no review would be complete without discussing a few of the remaining tradeoffs.

Weight: What? Didn’t I just rave about the weight being a pro of these wheels? Well, yes… in comparison to my existing budget friendly Roval CL50 wheelset. The RSLs really are astonishing light for a wide 62mm wheel, but if shaving rotating weight is you main goal is would be wise to look at the 37 and 51mm RSL options.

Price: The RSLs are not expensive relative to a top of the line carbon wheelset, but this is akin to picking the cheapest diamond ring… they still hurt the wallet. At $2700 before tax there certainly are cheaper options. The difference between the RSLs and a cheaper slightly heavier carbon wheel amount to incremental gains and only the buyer can decide if those gains are worth it. For me, the crosswind stability made these easily worth the extra cash.

Availability: At a time when you’d have better luck panhandling for gold than actually finding in-demand bike components, these wheels are no exception. I placed the order the day they were released and still had to wait 6 months for them to arrive. A quick search tells me they are still out of stock, but the actual current lead time of the RSLs is anyone’s guess.

Aesthetics: The wheels are beautiful and I love the way they look on the bike. However, they are understated. If you want to really turn heads with a loud in your face design, these aren’t it. I personally would have liked to see a more pronounced showcasing of the carbon weave. This is a bit nitpicky, but in my opinion needs to be listed as a con.

Final Thoughts

The Bontrager RSL 62mm wheel is an amazing product of research, development, and engineering. They simply FEEL fast. My best attempt to describe this is that as a cyclist I had rides where I feel great and rides I feel a bit flat. With the RSLs the great rides feel like adrenaline inducing joy rides where I’m hard pressed not to grin ear to ear, the flat rides feel a bit less so. Without controlled tests to show actual numbers that’s the best I can offer.

Will the RSL 62s make you a better rider?… I have no idea, but I am willing to bet you’ll love the experience.