Bontrager’s new Aelous wheelset is hyper-focused aerodynamics and speed- dubbed by the company as “the fastest wheel we’ve ever created”. We had a chance to put them through the paces and races – do they live up to the claims?

The line is an expansion of the previously released Aeolus 37 RSL (not to be confused with the 37V gravel wheel). This wheel is Bontrager’s departure from the Aelous XXX design, taking the new version to disc and tubeless/tubed only. Now, this shouldn’t be shocking, but Bontrager and the teams they supply are racing the wheels tubed or tubeless depending on the conditions. No more glue and stretching tires – just sealant or latex tubes.

A wider rim for aero gains

Bontrager focused much of their attention on the new rim shape of the Aelouls line. The 37 RSL (a new profile to the Bontrager wheel line) boasts a slightly wider 21 rim width and a 28 overall width. Bontrager wanted to keep these wheels as light as possible and concluded that the rim width, in conjunction with the class of riding this wheel would excel at, didn’t merit a broader cross-section.

In the deep end of the expanding Bontrager RSL family are wheel depths aimed at all-out speed and aerodynamic performance. The line has new options in the 51, 62, and 75mm deep profiles – giving the RSL family four options for different conditions.

The deeper section rims (51, 62, and 75mm) received a wider rim and closer attention to the aerodynamic performance of the wheel. Bontrager moved to a slightly wider 23mm inner width (over the 21mm inner on the Aeolus RSL 37 model) and a 31mm outer for these wheels. The team at Bontrager also maximized their development time on the new wheels by going straight to 3D CFD modeling from the beginning. Utilizing the number crunching abilities of super computers, they were able to run their programs non-stop until the best results were found in both low and high speed conditions. The overall findings were that the wider the rim (within reason), the better performance, proven to roll with less drag & rolling resistance, and provide a better aerodynamic connection with the tire. They found that the 23mm inner width matched with a 25mm tire yielded the fastest setup in testing.

Rim details

The new Aeolus rim is not hookless but has a beefy shape thanks to its 31mm overall width. The wheel is crafted from Bontrager’s RSL-level OCLV carbon, a construction they claim comprises some of the lightest and strongest carbon fiber available. Compared to the Aeolus Pro wheels, the RSL level wheels have a raw carbon finish that shows the individual carbon sheets in the right light.

The trim color is a deeper black/carbon, with a laser etched-style logo on the rim. In recent years Bontrager changed the chemical finish of their carbon to stop fading and discoloration that happened in the early (2011) versions of the Aeolus D3 wheels.

Hub details

With a new wheel comes an updated hub, and the Bontrager RSL is no different, employing the latest high-end road race hub from the masters at DT-Swiss. The Bontrager-styled DT-240 EXP hub is the same across the entire Aeolus RSL wheel line.

Bontrager’s take on the DT-240 EXP is different than others using the same base hub on their high-end wheels. Bontrager plays up the flange and gives a shield over the spoke head – adding styling that sets it apart from the sea of straight-pull aesthetics. This stying uses a unique straight pull spoke design, with a spoke head that wedges into the flange cutouts.

The hubs come stock with 12mm endcaps and an 11spd freehub body. You can swap the end caps for 15mm for those wondering, and the freehub body is compatible with other Ratchet EXP freehubs like XDR.

Actual Weights

  • Bontrager Aeolus RSL 51 weight: 1460g/set
  • Bontrager Aeolus RSL 62 weight: 1516g/set
  • Bontrager Cloth rim strip: 24g
  • Bontrager plastic tubeless rim strip: 60g
  • Bontrager tubeless valve core: 6g

Hands-On: Aeolus RSL 51 – Jordan

Set up

Like all Bontrager wheels – the new RSL 51s arrive with a reinforced cloth rim strip for tubes and a plastic Bontrager tubeless strip. We opted for the tubeless strip for my setup – following the directions of the manufacturer. The strip itself is 60g per strip, so if you did choose to roll with another tubeless setup – say Stan’s tape, you can lighten this wheelset even more.

We had no problem mounting Bontrager’s new AWT road tire and seating it with a floor pump. It took a few spins of the wheel in hand to completely seal, but that’s common.

Installing the wheels, adjusting the brakes, and spinning them up, I couldn’t feel any oscillation, something that I find common in the stand. The bike stayed nice and still with a slight twitch now and then, a sensation similar to adding the Silica Balance Shield.

The 28mm tire measured out to a wider 29.50mm and fit my road frame nicely. This ballooning effect could be troublesome to riders looking for the maximum-width tire, but some research could quickly narrow the scope. I don’t see any riders fitting a 30mm tire in an aero frame without clearance issues – but I’ve been wrong before.

The ride

I stuck to the fast tarmac close to home for my first couple of rides, where the winds are plenty and the roads are choppy. I started the pressure pretty high at 80psi front and rear to see how the tire felt. I quickly noticed that was too much air after hitting some local country roads and dialed it down to a smooth 75psi. The difference in comfort with the lower pressure is instantly noticeable, but I didn’t feel the tire squirm or bob – I felt very in control.

Rolling on open, unrelenting, wind channel roads, I found the wheels to hold steady very well. When gusts of wind would come either from passing cars or what have you, I felt a slight tinge of movement – like getting off the front from taking a pull, but that’s it. I liked the ease at which the wheels maintained speed; there was no soft spot, just steady rolling with no need to add effort to keep balanced.

Climbing and descending with the Aelous RSL 51s is like riding with a much lighter wheel. The 51mm deep wheels don’t feel like a hindrance; they spin up easy on super steep pitches and give the sensation of gaining speed in switchback style descents.

For racing, I swapped the Bontrager AWT for some Pirelli P Zero Race TLRs, and these brightened up the wheels a lot. The supple rubber gave me sensations of riding my tubular and was still riding at a comfortable 75psi.

Sitting in the pack, the Aeolus RSL 51s felt awesome. When surges in the group hit, I responded with less power (maybe I was feeling good that day) and stayed comfortable. In the wide-open sprints or trying to bridge up to a group, these wheels feel like an extra gear – holding speed easily and abundantly.

My only complaint about the wheels is at the $2400 price tag, and they should come with a wheel bag or something to protect your investment. Yes, all the Bontrager Aeolus wheels come with the “Guaranteed for life” carbon warranty, but I was bummed to see no bag in the box.

Hands On: Aeolus RSL 62 – Zach

When it comes to aero wheels, I typically reach for depths of 50mm or less. Most of my riding is a solid mix of wide open flats where having an aerodynamic edge is a huge benefit, and steep, short punchy climbs where the opposite is true. But with Bontrager claiming big benefits in both high and low speed cross winds and a fairly light package for a deeper wheel, I requested the RSL 62s.

The timing of this launch coincided with the new SRAM Rival eTap AXS group, which means that so far, all of my time with these wheels has been on board that test bike – a Mosaic RT-1d.

Setup:

These days, I usually go straight for the 28mm tires for the road. I’m fully on board with the “wider tires are faster” school of thought that is gaining traction. However, Bontrager says that these wheels are fastest (at least aerodynamically) when fitted with 25mm tires. So I went with that recommendation and mounted up a pair of 700c x 25mm Bontrager R3 Hard-Case Lite TLR road tires.

Shown with Vittoria Corsa Control TLR Tires

While the hot patch on the tire may say 25mm, when mounted to the 23mm internal width rim, the tires actually measured just over 28mm wide. That makes the tire almost as wide as the rim where the two meet.

Using the included Bontrager plastic tubeless rim strips, setting the tires up tubeless was very easy. I will say that one of the plastic strips had a visible cut in it – that I noticed before mounting fortunately. You don’t want to use a strip with a hole in it, so a quick inspection of the strip before installing is recommended.

To install the strips, I start by lining up the valve holes on the strip and the rim, and then insert the tubeless valve to prevent the strip from shifting as you snap it into place. Then simply stretch it over the rim until it snaps in. You may have to massage the edges of the strip down into the side pockets of the rim channel – I did this (gently) with the flat tip of a plastic tire lever just to be sure everything was seated properly.

One of the big benefits of the plastic strip design is that it provides a perfectly flat seat for the tubeless valve. As a result, you don’t have to crank down on the valve nut to try and get it to seal. The whole process is much less finicky than installing tape, and results in a nearly air tight seal allowing the tires to easily pop into place with many floor pumps. I was able to install both tires without using any tools – the fit is snug, but not so tight that it requires tire levers.

It’s nice that Bontrager gives riders an option when it comes to the tubeless tech. For those that just want the absolute easiest set up, the plastic strips are hard to beat. But for those who want the lightest set up, the typical tubeless tape will get you there.

Once mounted with Bontrager sealant, the tires have held air quite well – only leaking down a few psi between rides. I make it a point on new wheels to try and install and remove tubeless tires without using any tools to find out how easy tire installation is when using proper technique. Both the Bontrager and Vittoria tires easily went on and off without issue, and without having to resort to a tire lever – so if you’re struggling, make sure to pinch the tire beads into the center of the rim channel which gives you more slack to work with.

The Ride

Out on the road, the RSLs immediately hit you with a sound that is unlike anything else in the Bontrager line up. I’ve had quite a bit of time on the new Bontrager Aeolus Pro wheels, and the RSLs sound, and feel quite different. They just have that lively reverberation that only super light, deep carbon wheels have. Coincidentally, they also act as a megaphone for any bike-related noises. So if you have a disc brake rotor that is slightly rubbing, you’ll probably notice it more with these mounted up.

After riding the 62s on some very windy days that included some very exposed, high speed descents I’m inclined to believe Bontrager’s claims of offering improved stability in high and low speed conditions. Blasts of cross winds that normally would lead to a white-knuckled grip of the bar were shrugged off with a slight tug at the front wheel. I wouldn’t reach for the 62s for a day of big climbs and descents, but for those rides with plenty of flats and gradual hills, the wheels are surprisingly versatile. More importantly, on wide open stretches of pavement where there’s no hiding from the wind, the Aeolus RSL 62s do a admirable job of cutting through the wind, maintaining their heading all while giving you a noticeable boost in speed.

Initially set up with Bontrager R3 Hard-Case Lite TLR tires which have proven to be quite durable, I wanted to try out the wheels with something else for the sake of testing. Moving to a pair of Vittoria Corsa Control Tubeless Ready tires also in 700c x 25mm size, the ride got even sweeter. Like the R3s, these 25mm tires measured over 28mm on the wider rims, and sealed up tubeless without issue. Running 70psi in both tires, the ride of the Vittorias was ridiculously supple and seemed to improve cornering confidence on high speed turns.

Conclusion

The Bontrager Aeolus RSL 51s are a performance wheelset and come at a performance price, but if you want a wheel at the sharp end of aerodynamics – they are worth a hands-on look. The price is what you’ll pay for a wheel of this quality from most carbon race manufacturers. Still, the warranty coverage is fantastic—highly recommended for those who race road and crits as a do-it-all set up with climbing ability.

20 COMMENTS

  1. “I’m fully on board with the “wider tires are faster” school of thought that is gaining traction.”

    Not to claim that this is definitely debunked, but here’s something:

    https://www.bicyclerollingresistance.com/specials/grand-prix-5000-comparison#drop45

    Wider tires only win if you over-inflate them. Once you set them up for the same absolute deflection (ie. same level of “comfort”) the rolling resistance between 23/25/28/32 is basically the same.

    Wide tires have more headroom for comfort and traction, but at the cost of aerodynamics and weight. Rolling resistance pretty much cancels out when set up with comparable ride characteristics.

    • “Wider tires only win if you over-inflate them. Once you set them up for the same absolute deflection (ie. same level of “comfort”) the rolling resistance between 23/25/28/32 is basically the same.” – true, but only for the smoothest roads. Wider tires cover the bumbs/small holes much better than narrow ones.

      • No, that’s exactly what they tested for. When inflated so that each tire would absorb the same height of bump (in this case 4,5mm), they then got almost same exact rolling resistance for each width.

    • On these wheels, a 25mm tire measures 28.5. Same weight as a 25mm tire on any other rim, and Bontrager claims this setup also yielded the fastest set up in terms of aerodynamics. Then the wide rim allows you to run lower pressures to get a more compliant ride, so maybe what I should have written was that I’m fully on board with the “wider rims are faster”w which result in wider tires by default?

      • Fair enough, but there’s a widespread belief these days that wider tires are simply faster while also being more comfortable (due to better absorption of road imperfections or some such). Case in point, above.

    • I appreciate the efficiency! Ask your market research people to figure out the most impressive bar graph, then manipulate the scales to show your data in (virtually) the same graph across three scenarios.

      So yeah, totally with you on how disgraceful these are… but I guess people who read the scale (or read anything) are a minority these days.

  2. i’m sure these are nice wheels. But we’ve entered an era (actually some time ago) where $2500 wheel sets are pretty much the norm. Kinda bums me out.

    • Yeah, the price is pretty wild. Fortunately, there is a new generation of much more affordable carbon wheels like the Aeolus Pro which are close in performance (and probably better performing than top of the line wheels 10 years ago). You could buy two sets of Pros in different depths for almost the same price as a pair of RSLs.

      With that said, the RSL wheels are definitely a big step up from the Pros, but you’ll have to pay for it. And as Jordan said, at this price, they should really include a padded wheel bag to protect your investment!

  3. As I said in the first post about the product, I can’t for the life of me see a non-cynical reason why they would feel the need to come up with another proprietary spoke head interface. This, and all the other press about it, just kinda says “it has this” (if even mentioning it) but doesn’t give a reason for it. Even a purely marketing reason like “this unique spoke head design allows for clearance for the small cover – called the Bontrager Spoke Cowling – over the spoke heads at the hub, producing a fairing like effect and smoothing airflow around this otherwise busy, turbulence inducing area of the aerodynamic system” would be nice.

    These are visibly different than the older T head design that some Bontrager and Roval wheels used a few years ago, which already weren’t always widely available, especially to an IBD that wasn’t tied at the hip to Big T or Big Red S (but could be made in a pinch by squishing a “regular” straight pull spoke head in the vise).

    From the image, the spoke head on this seems to be a three dimensional trapezoid – I’m not sure what that would be called besides a trapezoidal prism (9th grade geometry was a long time ago) – and this article even specifically calls it a “..unique straight pull spoke design, with a spoke head that wedges into the flange cutouts.”

    I’d love to hear a reason they did this, without one it just makes it seem like this is an attempt to capture another tiny bit of revenue by directing money from even something as simple as spoke replacement through Trek. And I’m sure this relatively small batch spoke will be a couple dollars more expensive than a normal DT Aerolite, and certainly more than a CX Ray straight pull.

      • Thanks, Jordan. I look forward to hearing back.

        I guess what I mean when I say I can’t think of a non-cynical reason for this given current information is that, essentially every other time there’s a proprietary or novel spoke design, there’s at least a stated reason for it AND it’s different enough from a/the existing “standard” (read: stainless steel spokes) that you can kind of talk your way into it. And a lot of the time, it’s the reason you get that wheelset, not something hidden in the details.

        Berd says use these shoelaces instead of stainless steel, and you’ve got crazy light spokes with unique ride characteristics. You can not think it’s worth the price delta over a CXRay – about double the cost per spoke, $8ish vs $4ish not including any different cost associated with a wheel builder’s labor – but there’s an obvious reason for it: they’re light

        Industry9 says we use these proprietary aluminum spokes because they’re lighter, maybe stronger in some ways, and most importantly, can look ridiculously cool if you want to get wild with your color combos.

        Spinergy is still out there somewhere doing Spinergy things in the name of lightness and general weridness.

        My friend Andy Goh of Wheel Angel & Velotechnic has his wheels with carbon fiber spokes available, again in the name of lightness and maybe strength.

        In all these cases, you’re not just incidentally locking yourself into funky hard to get proprietary spokes that may be hard to find replacements for three or four years from now when you buy one of those wheels, you’re probably buying that wheelset specifically BECAUSE of the spoke design. Something about it spoke to you, pun not intended, and go into it willingly.

        With these wheels, it seems like it’s a little detail that’s buried in there that will make these less consumer friendly sometime down the line when a spoke breaks. And here it doesn’t seem like something the standard consumer of these wheels is going to know about when they got into it. BERD, Spinergy, I9, and various iterations of carbon spokes are all blatantly obvious that something is funky. Whereas with these it just looks like a regular straight pull hidden behind a little cover or cap (like old Zipps) – even pretty serious bike tech dweebs wouldn’t catch on that these are funky and proprietary because they’ve hidden it.

        As I said in the parent comment, if Bontrager had just sent in the marketing guru and had them change up the ad copy to invent a nonsensical reason for doing them we’ll call it Bontrager Imagineered Spoke Cowling: Uniquely Integrated Technology (BISCUIT, for short), then it wouldn’t seem (to a cynic) like a sneaky, somewhat anti-consumer way to forcibly increase reliance on a Trek Authorized Service Center.

        • These spokes are not a Bontrager marketing thing. They are DT Swiss T-head spokes, the same as they use on their DT Dicut wheels, and which they have been using for 7? Years already. Not to be confused with Straight Pull spokes on their other wheels. Only the top of the line road wheels from DT Swiss come with their T-head spokes.

          They make for some great Aero hubs with thin flanges, compared to their not so aero Straighpull spoke hubs.

          • I’d be happy if these were normal t head, but for some reason they don’t quite look like it to my eye in these photos – to me it looks sort of squared off rather than having the “classic” t shape sort of point.

            It’s entirely possible it’s just the angle of these photos that obscure the “pointiness” of the spoke head, and frankly I (obviously) hope it’s just that, because I’m obviously irrationally disturbed at the idea of another new spoke standard for no reason. But given what I’m perceiving from these photos, plus the fact that it describes a “unique straight pull spoke design” leads me to think it’s something different. But I’d be thrilled (perhaps too strong a word) to be wrong.

  4. “This stying uses a unique straight pull spoke design, with a spoke head that wedges into the flange cutouts”

    Not really unique. Same hubs that DT uses for their DICUT wheels, and the same T-head spoke that has been available for quite some time now. I don’t see what the big controversy is.

      • Ok yes, I see it now. And you are right, it’s Trek is basically forcing you to go to their shops just for a simple spoke. Soon they will have their own proprietary air that can only be had at their service centers.

    • OK, we just confirmed with Bontrager that these ARE a standard DT Swiss Aerolite Straight Pull T-head spoke. The Bontrager hubs seem to use a more captured spoke head slot than other hubs, which obscures part of the spoke head – which is why they looks slightly different. Trek does stock them since they aren’t the easiest to find, so replacements can be found through any Trek Dealer.

      • Hard to tell in those pics for sure. I just din’t want to take anything away from the time invested Mr. Walrus has in this. Still agree with the premise of availability though, just not in so many words. Even though this isn’t another proprietary spoke, T-heads have been around a while, but only to the OEM’s. Almost impossible for independent shops to source. Not surprised really, it’s modus operandi for a big box brand’s to keep everything to themselves, even something so simple as a spoke.

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