BMC Kaius Review - Faster Than Your Gravel Bike

BMC markets the Kaius as a gravel bike in an increasingly-crowded gravel bike world. However, it isn’t even BMC’s first foray; rather, that goes to our ever-popular URS. The URS was unique for having built-in rear suspension (if only barely) and mountain bike-centric geometry. It was a vision of gravel bike geometry against a gravel bike market that was still trying to figure out how they wanted a bike to handle. The BMC Kaius in comparison swings a bit back from mountain bike inspiration and toward the drop bar market.

More specifically, it draws a whole lot of inspiration from the Teammachine SLR race road bike.

 

The Teammachine SLR road bike is positioned as the brand’s race road bike, with only minimal concessions to comfort at the altar of the aero efficiency gods. Does the BMC Kaius gravel bike make sense in the gravel bike market, much less alongside BMC’s own URS gravel bike? We break it all down.

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Kaius Frame Details

BMC has an enviable design language. Folks recognize the sharp angles, trim bike profiles, and uniform fonts they use across all models. They even were at the forefront of internal cable routing, staring with the BMC Roadmachine in 2016. The BMC URS release saw those unique BMC aesthetics brought to the gravel bike world. Kaius enters a market far more diversified than before, with other bikes like the Cervelo Aspero that match the traditional BMC design brief. Where does Kaius fit in then?

To start, the Kaius feels to be what is effectively a gravel version of the BMC Teammachine SLR01. For one, the bike is unapologetically made for going as fast as possible on gravel. Much of that bears out in the geometry - more on that shortly - but you can see it in the core weight numbers. Here are the details:

• A 56cm frame weighs in at 910g, with an uncut fork weighing in at 400g. 
• A proprietary BMC D-shaped seatpost weighs in at 160g. 
• A one-piece ICS Carbon Aero Cockpit designed specifically for Kaius weighs just 315g. 
• A complete module (of the above components plus hardware) weighs 1785g.

These are numbers generally associated with a race road bike, and lighter than most other gravel bike frames. 

Now on to that one-piece setup. The one-piece setup offers up the expected line of benefits, namely lower weight, improved stiffness where you want it, and improved aero benefits when paired with the integrated cabling. But what’s unexpected is that the one-piece bar comes in just one particularly narrow width: a 36cm center-to-center width at the tops and the 12.5-degree flare increases the width to 420mm at the drops. BMC says the standardized narrow width follows along with road racing trends, though it should be noted that Teammachine SLR01 frames with their own one-piece stem aren’t locked into the same bar width across sizes. It should be noted that different frame sizes receive different stem lengths. 

This one-piece handlebar setup is found only on the Kaius 01 ONE; anyone looking at other Kaius models will not be locked into one bar size, though the carbon bar and stem combination will be heavier. Want to swap bars on the Kaius 01 ONE? Our custom bike program could make that happen. 

Really, the one-piece bar here is one example the Kaius wearing its Teammachine relationship on its sleeve. The Kaius has the same closed thru-axle dropouts that hide visible driveside dropout threads, accentuated by similarly beefy tube shaping that seems vaguely aero-influenced. It even uses BMC’s Aerocore concept, or the Swiss company’s way of integrating the bottle cages into the frame to make the frame more aerodynamic with water bottles than without.

Other critical bits to note: Kaius offers a max tire clearance of 700c x 44mm tires, and that’s quoted with a minimum 6mm clearance on each side of the tire. Kaius is compatible with both 1x and 2x drivetrains with a front derailleur. And of course, there are two mounts for water bottles on the frame, a third mount under the downtube, and a mount for a top tube bag.

And should riders want to increase the Kaius’s gravel orientation, Kaius can be swapped for a 27.2mm seatpost with a shim, and therefore a 27.2mm dropper post. Bikes that use the two piece ICS stem can swap for BMC’s MTT stem, a partnership with Redshift Sports that adds suspension vibration damping at the stem.

Geometry

For a bike that pulls so many features from the Teammachine, the geometry still skews toward the URS and its progressive gravel geometry. The most critical part of this comes form the long reach measurements across all sizes of the Kaius, which when paired to a shorter stem as spec’d by BMC, is awfully reminiscent of BMC. Stack height across all sizes quite a bit lower too, and more in line with the Roadmachine endurance road bike. 

Elsewhere you’ll see numbers reflective of a racey gravel bike. That includes the short 420mm chainstays, steeper head angle, 73-degree seat angle across all sizes, and lower (for a gravel bike) trail figures that indicate a bike that’ll have just a bit more responsive steering. In fact, the 68mm trail figure isn’t too far off from a standard road bike much less other racey gravel bikes.

One final note here: 80mm bottom bracket drop! We tend to pay attention to bottom bracket drop moreso than the average group of bike nerds because of how often we’re descending down canyons at high speeds. A low bottom bracket isn’t always a one-way ticket to increased stability, but we’re excited to see increasingly lower bottom brackets in the name of straight-line stability. Dave Moulton might disagree with our assessment of low bottom brackets, but there’s a reason why we’re not all riding bikes with zero bottom bracket drop: they make you feel tippy and like you're riding on top of the bike. A low bottom bracket makes you feel like you're riding more in the bike, providing much of that straight-line stability we crave. 

In short, the Kaius geometry suggests a bike that will make the rider feel like they’re sitting in it, rather than on top of it. 

Kaius Builds

BMC Kaius is launched with three builds: Kaius 01 ONE, Kaius 01 TWO, and Kaius 01 THREE. Of course, if you want a build that’s different from what BMC offers, we can do that too. 

The Kaius lineup starts with the Kaius 01 THREE. It features a two-piece stem that hides cables in the frame and can be paired with any handlebar; here it has an alloy bar and stem. This model receives a SRAM Rival AXS 2x12 groupset using CRD 400 carbon wheels, Pirelli Cinturato Gravel H 40mm tires, and a Fizik Vento Argo R5 saddle.

One step up is the Kaius 01 TWO. It also features a two-piece stem that hides cables in the frame and can be paired with any handlebar but upgrades to a carbon handlebar. This model receives a SRAM Force eTap AXS 2x12 groupset paired to Zipp 303 S carbon wheels, Pirelli Cinturato Gravel H 40mm tires, and a Fizik Vento Argo R3 saddle. This is likely our favorite build as the Force AXS groupset cuts quite a bit of weight from Rival, and the Zipp wheels are one of our favorites.

At the top of the lineup is the BMC Kaius 01 ONE. This is the only model to feature the one-piece handlebar and stem, and is color-matched to the frame. This one uses a SRAM RED AXS XPLR 1x groupset, Zipp 303 Firecrest wheels, Pirelli Cinturato Gravel H 40mm tires, and a Fizik Vento Argo 00 saddle.

Our Take

While many might scoff at the idea of a gravel bike essentially being a road bike, what we’ve seen from our clients use of gravel bikes is essentially that: a road bike with bigger tires. The Kaius adds a whole lot more stability to the mix than a standard road bike, however. And paired with it's aero intentions, the Kaius looks to be best suited to those who are grinding out long miles in the saddle in wide-open spaces with nary a paceline to brace the wind. Translation: its a gravel race bike through and through. 

The narrow 36/42cm bars on the Kaius 01 ONE might steal headlines, but the meat of the Kaius lineup receives traditional bar widths. If you’re looking for a gravel bike that does the road and singletrack combination it bit more seamlessly, BMC is happy to offer up the URS, a bike we think does that with ease. Kaius is a gravel bike that performs at it's best when you’re on you’re own on wide-open farm roads without a paceline to break that inevitably nasty headwind every gravel race seems to have.

That the Kaius strives to be as efficient as possible won’t resonate with everyone. It is a more specialized piece than the traditional jack-of-all-trades gravel bike. For those folks, there are a ton of other gravel bikes that’ll fit the bill. But for those who resonate with the Kaius mission prompt? We think there are few gravel race bikes that fit the bill better.

Conclusion

Gravel riding is different according to the region you’re riding. Gravel bikes are therefore pitched as a Swiss Army Knife to tackle any array of conditions you might see. But the fact of the matter is that not everyone needs - or wants - something that can do it all.

For those who will spend a lot of time riding against a strong headwind, or want to cover miles as efficiently as possible on the dirt and pothole-riddled roads we face, the BMC Kaius is a formidable tool. And if it's not the tool you need, no worries: there are plenty of gravel bikes to choose from.

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