We review the world championship winning Cube Aerium C:68X SLT triathlon bike

Cube began developing the Aerium C:68X back in 2020, quietly refining concepts and shapes long before the wider world knew what was coming. By the time the first prototypes were revealed in 2022, it was clear Cube wasn’t simply updating its triathlon platform—it was chasing every last aerodynamic gain the rulebook would allow.

Fast-forward to today and the results speak for themselves. An Ironman world title and a record-breaking bike split from Lucy Charles-Barclay have cemented the Aerium C:68X as a bona fide weapon at the sport’s highest level. All those hours of CFD modelling, wind-tunnel testing, and meticulous component integration appear to have paid off handsomely for the pros.

But cutting-edge performance at the pointy end of the field doesn’t always translate seamlessly to the needs of everyday athletes. So the question remains: beyond its elite pedigree, is the Aerium C:68X also one of the best triathlon bikes for age-groupers? Let’s find out.

Cube Aerium C:68X SLT builds

The Aerium C:68X is now available in three full bike builds starting from £6,499 (US pricing N/A).

The SLT version that we got our hands on (£8,999) is the top-of-the-range model, with 12-speed Shimano Dura-Ace shifting, 80mm carbon triathlon wheels and Cube’s unique frame-integrated hydration system.

The C:68X may look similar to its predecessor, the C:68, at first glance, with the unique ‘Twin Head Tube’ for claimed aerodynamic improvements carrying over.

‘3.6 watts faster’

However, Cube claims its new tri superbike is 3.6 watts faster, having refined every part of the bike apart from the Twin Head Tube, seatpost and between-the-arms (BTA) hydration system.

The handlebars are smaller, the head tube narrower and the fork deeper in the name of aerodynamics.

The extensions have also changed shape and fascinating things are going on inside the frame.

The weight has dropped, too. The full bike comes in at 9.1kg / 20lbs without the in-frame hydration system and around 9.7kg / 21lbs with it.

Cube has gone big on versatility with the Aerium C:68X, supplying a huge array of accessories to suit your needs.

The aerobars, with extensions courtesy of Profile Design, come with all the riser blocks, bolts and washers you and your bike fitter will need to achieve your perfect position. There’s plenty of fore/aft at the seatpost too.

When it comes to storage and hydration there’s even more choice. You have the option to run both BTA hydration and the new in-frame hydration system together, or neither, thanks to all the modular fixtures and fittings.

The in-frame hydration is filled via a bladder that fits into the frame just above the bottom bracket/ Alternatively the space could store a puncture repair kit.

You drink from the bladder via a straw that pops out from the front of the top tube storage box, or just straight out from the top tube if you’d rather take the box off.

Cube Aerium C:68X SLT ride and handling

Trickery aside, the Aerium C:68X is simply a phenomenal ride. It’s instantly noticeable how much less effort is needed to make it go fast compared to the best road bikes or lesser tri bikes. In a straight line it’s an absolute bullet.

Acceleration is impressive for a tri bike. On hills I didn’t feel like weight (from the bike, anyway) was holding me back.

The meaty tubes and bottom bracket area make the bike feel assured and stable. Even with 80mm aero wheels in February, it handled very well in crosswinds.

A wheelbase of just over one metre on a size medium frame adds to this stability. But this slightly compromises cornering.

The Aerium isn’t the very sharpest bike into corners. However, you’re more likely to ride it on rolling terrain rather than twisty urban circuits. So I appreciated the planted feel of the bike.

The bike also has plenty of bump-taming comfort, a boon for UK-based triathletes.

I felt confident riding over rough roads in my aero tuck. The overall impression I got during my test rides was smooth and stable.

I’m a big fan of the Profile Design 43 ASC carbon extensions, with the ergonomic shape in the middle of the bar providing a comfortable touch point for the forearms.

The base bars are also comfortable enough to grab for extended periods while climbing. You might want to add extra bar tape for long races with significant elevation.

Superb spec

The rest of the components and finishing kit, as you’d expect for a top-of-the-range bike, are superb.

Hydraulic disc brakes provide plenty of stopping power; Selle Italia’s Watt saddle is one of my favourites for tri; the Newmen Advanced SL R.80 Streem wheels mated to Continental GP 5000 TT tyres is a rapid combination; and Shimano Dura-Ace Di2 shifting is as good as it gets in 2025.

You can shift from the base bars or extensions. The 54/40t chainset paired with an 11-30t cassette provides a wide range of gears with plenty at the top end.

Cube Aerium C:68X SLT hydration and storage

The biggest change to the Aerium C:68X over its predecessor is the all-new in-frame hydration, which Cube says was influenced by Charles-Barclay’s preference to be as self-sufficient as possible on the bike.

Using the BTA hydration, in-frame bladder and bottle inside the frame means you could carry well over two litres of liquids, for example water or electrolyte drinks, reducing time spent refilling at aid stations.

Cube supplies two bladder sizes for S/M and M/L frames, with a 750ml capacity for the larger one.

The sheer number of tubes and attachments with a tiny space above the bottom bracket to fit it all into was quite baffling at first, and routing the refill and drinking tubes through the down tube and out through the front of the storage box was quite tricky.

Mid-ride refill issues

When all became clear I couldn’t help but be rather impressed (mostly with myself for working it out, despite sparse instructions) and the system is also very modular, with lots of possibilities to refine the set-up to your preference.

For example, there’s an in-frame funnel if you want to use the hydration system without the top tube storage.

It was easy to drink from while riding, although there’s quite a strong plasticky taste, but filling up on the fly wasn’t so easy.

I found myself needing to shake the refill port to get the liquid to drain into the bladder, which wouldn’t be ideal mid-race and could negate any time saved by using the bladder for additional hydration in the first place.

The BTA hydration, which affixes magnetically and can hold up to 750ml of liquid, worked brilliantly, and was much easier to fill on the fly.

While I appreciate the ingenuity of Cube’s engineers, my preference would be to stick with this plus a water bottle for hydration and use the frame storage box for storing tools and/or essentials, with the top tube storage used exclusively for nutrition such as energy gels or energy bars.

It’s also worth noting that the frame storage box itself is also quite difficult to open, requiring a lot of force and some nails to prize it out.

Cube Aerium C:68X SLT bottom line

To conclude, I was highly impressed with the Aerium C:68X, appreciating its superb speed in a straight line, predictable handling and versatility.

You can chop and change the set-up and accessories to suit almost any triathlon distance or positional preference, giving you more value for your £8,999.

While that’s a huge chunk of cash, it’s actually less expensive than top-end bikes from numerous competitor brands.

The new in-frame hydration is the party piece aesthetically, but I was more impressed by the less obvious improvements such as the narrower front end and lower weight.

While some will appreciate the huge volume of liquid you’re able to carry from the outset of an Ironman race on the Aerium C:68X, I found the in-frame hydration system a bit too awkward, and wouldn’t opt to use it myself.

In the Aerium C:68X, Cube has delivered a worthwhile upgrade over the outgoing model, though I believe it could be refined further still.

For more go-fast gear, don’t miss our guides to the best aero road helmets and the best tri-suits.

Meet our tester

Jack Sexty is an expert cyclist, bike handler, and connoisseur of all things bike and triathlon related. Jack used to be part of the 220 Triathlon team before starting up his own cycling publication. He knows what it takes to build and ride a high-performing triathlon bike and is the best in the biz for sniffing out the best bikes to recommend to triathletes of all abilities.

Cube Aerium C:68X SLT specs

Price:	£8,999 (US pricing N/A)
Weight:	9.1kg / 20lbs (9.7kg with hydration accessories)
Frame:	Aerium C:68X
Fork:	Aerium C:68X
Gears:	Shimano Dura Ace Di2
Brakes:	Shimano Dura Ace BR-R9270 Hydraulic Disc
Wheels:	Newmen Advanced SL R.80 Streem
Finishing kit:	Continental Grand Prix 5000 TT tyres, Cube Aerium C:68X Cockpit System, Cube Hydration and Storage System, Selle Italia Watt SF Magnesium saddle
Buy if…	You want a versatile tri bike for all distances, and are prepared to splash the cash