A Hands-On Review of the 2023 IMWC-Winning Cube Aerium C:68X

If you didn’t see Cube’s new tri bike during the 2023 Ironman World Championship women’s race coverage, you were probably watching the race with your eyes closed. For four hours, 32 minutes, and 29 seconds Great Britain’s Lucy Charles-Barclay rode her Cube Aerium C:68X alone down the Queen K with no one blocking her view. Not only did Charles-Barclay break the tape for the win, but she set a new overall course record and had the fastest bike split of the day.

For those who are unfamiliar with the Germany-based bike brand, Cube has a very big following in Europe, but it’s rare to see their bikes stateside. To illustrate: At last year’s Ironman World Championship bike count, Cube ranked 11th in Nice at the men’s race; in the women’s race in Kona, Cube barely made the list at 19th.

So I was fortunate enough to get my hands on a Aerium C:68X SLT—similar to the one Charles-Barclay rode to her win, though she used DT Swiss Wheels and a custom Cube cockpit—to test for a few weeks during one of the arguably most rainy years in Southern California’s history. Read on for my real-world observations and review.

Cube Aerium C:68X Review: Stats, Features, and What’s New

So first we’ll start with a little background on the Cube Aerium C:68X. Launched last year, we had already seen Charles-Barclay on a prototype version of the bike at the 2022 edition of the Ironman World Championship. Both versions were different than the most recent previous model, the Aerium C:68 TT, in that the C:68X boasts integrated in-frame hydration—in addition to the already-existing disc brakes, on-frame nutrition storage, and included between-the-arms (BTA) hydration storage that were found on the C:68 TT. In other words, the new C:68X has added that in-frame hydration bladder (located just above the bottom bracket) and has improved aerodynamics (3.63 watts faster than the Aerium C:68), steering, and overall weight—all according to Cube.

The resulting bike is unique from other “superbike” options in many ways, but also similar at times: Frame highlights include a very unusual “Twin Head Tube” with a head tube cutout that’s meant to increase aerodynamics and improve steering performance (more on that later), a super-low seatstay for aerodynamics, a very deep fork (likely to help with integrated disc-brake aerodynamics), the aforementioned included BTA integrated hydration, built-in top-tube nutrition storage, and the new in-frame hydration bladder/storage compartment above the BB. The front end is unsurprisingly integrated—as most superbikes are—but you do have the option to swap out extensions, and the model we tested came with the very-impressive Profile Design 43 ASC aerobars.

In terms of stats, we’ve posted the geometry chart far below, and the size medium Aerium C:68X SLT build we tested weighed in at a medium-ranged 22 pounds, 4 ounces with all integrated hydration/nutrition storage attached, but unfilled. Below is a table of comparably spec’d and sized tri bikes that I’ve weighed in person with similar hydration and nutrition storage features.

Cube Aerium C:68X weight vs. Felt IA 2.0, Scott Plasma 6, and more

Elsewhere, the Aerium C:68X SLT test bike specs included Shimano Dura-Ace Di2 12-speed all across the board with a Newman Advanced SL R.80 Streem 80mm wheelset—another stateside rarity. It should be noted that while my test bike used a front derailleur, Cube has a very elegant cover if you want to go 1x and sans front derailleur.

Cube Aerium C:68X Review: The Ride

Despite the overall beefiness of the frame—thanks to the overbuilt bottom-bracket section that houses the hydration bladder or storage, the huge head tube, and the larger-than-normal seat tube—I was immediately impressed by the smoothness of the C:68X’s ride quality. I found it to eat up both medium- and high-frequency bumps/chatter, and while big bumps weren’t soaked up quite as well (maybe thanks to the 80mm wheelset), it was still on the smoother end of superbikes I’ve tested.

When it comes to responsiveness, I found the C:68X to be lively but not exactly super snappy. There’s a small bit of lag on the windup when you stand up and hammer the pedals, but once the frame sets up, it doesn’t feel squishy or noodly. Given the size of the tubes I expected something super super responsive, but I wasn’t sad with its actual performance. Great for powering over rollers, but you probably won’t win a group-ride sprint if you’re not on the right wheel—but big whoop.

Cube Aerium C:68X Review: Handling

The smooth ride also paired well with the fact that this bike handles a straight line extremely well—even when tucked into an extremely aggressive front-end position far past the front hub and in buffeting crosswinds. Even with the 80mm wheelset, I was very impressed with the way the C:68X handled in blustery crosswinds on sketchy descents. Right out of the box, I was hitting near 40mph on windy descents without any…”puckering.”

Why is this important? Well, you don’t get fast bike (or run) splits in windy, sketchy places like the Queen K in Kona if your bike is blasting you all over the place and you’re puckered for hours straight.

My best guess is that the head tube cutout helps with crosswind handling (something Cube’s engineers tout), but the C:68X also doesn’t have the most aggressive side profile out there (though the fork is quite deep). I’d rate it somewhere in the middle of superbike side profiles, according to my “eyeball wind tunnel.”

In terms of cornering, the C:68X isn’t as scalpel-y as an Argon 18, but it’s very predictable through sweeping turns, and it gave me plenty of confidence to lay off the brakes or even change my line if need be. And of course in tri, comfort and predictability are two of the most important things—we’re not racing crits here.

Cube Aerium C:68X Review: The “Tri Stuff”

For sure I loved the ride and handling on this bike, and I was excited to see that Cube had finally joined the in-frame hydration rank-and-file. Only a few brands are still holding out against the rising tide of in-frame, onboard hydration—Trek, Orbea, and until recently Quintana Roo come immediately to mind.

But in practice, I struggled at first with the in-frame hydration bladder/system. (I had no problem with the fantastic BTA hydration system, however.) First, while Cube advertises 750mL of in-frame bladder capacity, I found it nearly impossible to fill the bladder to max, then fit it into the space allotted above the bottom bracket. (It’s also worth noting that you can use that compartment for either hydration or storage, not both at the same time without some bladder acrobatics. You can, however, use the battery compartment if you’re running the SRAM version, according to the Cube.)

I had to end up squeezing out about 25% of my fluid—which actually squeezed itself out via the refill reservoir on the top tube and all over the bike itself while I crammed it in. Some practice on how much to actually fill before fitting it into the bike is required.

Second, I had very little luck refilling the bladder while on the go via the top-tube-located refill reservoir at first. I was only able to get the refill reservoir to drain into the bladder after repositioning the hydration bladder into an optimal shape in the (very tight) storage area in the frame—which shares real estate with the Di2 battery—and tinkering with the bladder/hoses. If it wasn’t positioned correctly, the fluid would sit in the reservoir and never drain down.

This wouldn’t be the first frame design to struggle with onboard hydration refills—ironically Lucy Charles-Barlcay’s last sponsor, Specialized, was notorious for issues refilling the hydration reservoir in the last version of the Shiv. However, other brands have solved the refilling issue by using a box-like reservoir—like the Scott Plasma 6, the Ventum One, the Cadex Tri, and the Felt IA 2.0. Canyon’s latest Speedmax line uses a hydration bladder, but it’s located right next to the refill port and doesn’t require any hoses between the refill port and the bladder itself; it’s also given a bit more real estate where it’s positioned inside the downtube.

Elsewhere, the BTA hydration system is fantastic (it holds 750ml of liquid), with an ingenious little “door” for on-the-go refilling, and the top-tube nutrition storage is spacious and excellent as well. Both hydration hoses actually work very well—finicky bladder refill learning curve notwithstanding—and you won’t need to move from aero to get your fluids.

I also loved the Profile Design 43 ASC aerobar extensions, but of course that’s just a good spec call.

Cube Aerium C:68X Review – Final Thoughts

There’s a lot to love about this update to an already-excellent tri bike—the handling, the ride quality, the spec, and even the price. It has plenty of tri-specific features, and more than anything I really appreciate how much confidence the setup gives you in even the most aggressive of positions and conditions. Like many superbikes today, the Aerium C:68X is a great all rounder with only one little caveat.

However, I can safely say that even if you couldn’t refill the in-frame bladder while riding (which isn’t the reality, it just takes some specific positioning to get right), that would be ok. If you could only refill the fantastic BTA hydration on the go and simply start out of T2 with a full hydration bladder, that would probably be enough for most people and still be a net benefit overall. When you get the bladder working correctly, it’s actually a very good system all together.

And while I can’t quantify many of the benefits that Cube’s engineers are excited about—less side forces in crosswinds and better overall aerodynamics, for instance—I can say that the Aerium C:68X is a notably stable bike that certainly feels very very fast in all conditions. It’s no wonder that this is the bike of choice for the fastest woman in Kona, ever.

Cube Aerium C:68X Geometry Chart