BMC Kaius 01 One review

The BMC Kaius 01 One is the top-tier version of the Swiss brand’s first gravel race bike. It combines cues from both the adventure-focussed URS and the Teammachine SLR 01 road race bike to create a bike that is fast and capable off-road, and definitely one of the best gravel designs now on the market.

Its compact frame and compliant seatpost create a decent bit of seated comfort, while a fast ride feel is created in part by a sleekly integrated design and also by the narrow 36cm bars.

The bike is lightweight and – as usual from BMC – seems beautifully finished, with good attention to detail across the frameset and spec list.

A five-figure pricetag will exclude plenty of potential customers, though, and the bike’s white colour scheme, while undoubtedly looking beautiful on Instagram and on the shop floor, isn’t the most practical option for normal riders.

That said, in the Kaius BMC has taken an original approach to the gravel genre and has pulled it off nicely, as Pauline Ferrand Prevot’s win at the inaugural Gravel World Championships goes some way to highlighting.

BMC Kaius 01 One development

When BMC first properly committed to the gravel niche the brand released a bike somewhat out of left field. Considering the company’s strong road heritage, the radical design of its first gravel bike, the URS, looked to have more in common with BMC’s cross-country mountain bike platforms than it did its road-going ones.

Indeed, the URS shared features such as an MTT (micro travel technology) damper ported over from BMC’s hardtail mountain bikes, and its slack steering geometry was broadly similar too.

There was the sense that BMC was addressing gravel by pegging back from mountain bike territory rather than pushing on from road, as is the approach of many brands in their gravel designs.

It was an unexpected move, but BMC pulled it off with success. The URS was widely received as an innovative take on the gravel category.

In some sense then, the new Kaius is the gravel bike that everyone knew BMC could make, for it does seem more of an extension of road than a dilution of off-road. It meets the URS in the gravelly middle, but comes from the other direction.

It’s clean and it’s aggressive and its design bears strong resemblance to the brand’s road models, but is none the worse for taking a more familiar approach.

In fact, for the type of gravel riding I and many others enjoy, it could be even better than the URS it sits alongside.

BMC Kaius 01 One frameset

Unsurprisingly considering the Kaius looks so much like BMC’s road race bike, the Teammachine, the brand says the Kaius’ construction is designed to be stiff and light, and plenty of the truncated aerofoil tube profiles are shared between the platforms too.

Although not to the same extent as the brand’s aero Timemachime Road 01 bike, the Kaius also takes on the Teammachine’s ‘Aerocore’ feature, where the bike’s bottle cages are specifically shaped to integrate smoothly with the down tube and seat tube.

It’s a neat way that may create a marginal gain, but I do wish BMC would adjust its logo so the down tube cage footprint doesn’t encroach onto the top of the ‘B’ and ‘M’.

For a brand that otherwise finishes bikes to such an impeccable standard (for example, the enclosed thru-axle threads on the driveside dropouts are a delightful touch), it’s a niggle that should be rectified.

The Kaius isn’t all performance and no practicality, though. Its compact front triangle exposes plenty of seatpost in an attempt to introduce flex and improve seated comfort, while BMC says even though it has achieved an impressively light build weight of 7.7kg in the top spec Kaius, the frameset has actually been reinforced in areas likely to take knocks out on the trails.

Despite the Kaius’ raciness, tyre clearance is generous at a claimed 44mm for 700C tyres, and the bike is 2× compatible as well. BMC crams all these features into a road Q-factor by slimming down the driveside chainstay considerably.

However, thanks to the PF86 bottom bracket standard the bike uses – which in my view is one of the best standards a bike can use – BMC promises no compromise in pedalling stiffness thanks to the large tube widths PF86 allows.

BMC Kaius 01 One build

At the bike’s front end things take a turn back towards going fast. BMC has historically done internal cable routing better than most and here it’s employed its ICS cockpit design.

ICS routes cables inside the cockpit and down through an enlarged upper headset bearing via beautifully profiled spacers.

This approach is used to improve aerodynamics and smarten the looks on many of BMC’s top end road bikes, but interestingly the Kaius takes it a step further by using a narrow bar width that measures just 36cm at the hoods, reflecting the recent trend in trying to narrow the rider’s frontal area.

Trek’s new Madone is another recent launch that attempts to take advantage of the approach’s benefits.

What’s more, all bike sizes get the same width of bar. For larger riders or those used to wider bars, this spec choice will likely take some getting used to (particularly when climbing out of the saddle, due to the reduced leverage).

Based on my understanding though, the science does tend to universally stack up regardless of how an individual subjectively gets on with that bar width – narrower bars generally make the rider and bike system more aerodynamic.

If it’s a deal-breaker though, the Kaius models below this one use more conventional, size-specific bars and stems, with which this bike is compatible too.

The more rearward finishing kit is less controversial. The Fizik Vento Argo 00 saddle is both comfortable and light, and the Kaius seatpost is excellent.

Despite being light, its levels of fore-aft flex were excellent, being enough to meaningfully improve seated comfort without being too much as to feel unstable.

While the specced seat post is D-shaped, the Kaius accepts a regular 27.2mm round post in conjunction with a shim in a similar manner to the Giant Revolt Advanced.

It is excellent to see BMC both offer an excellent original component here as well as the option to easily change it should the user want to customise their bike.

The wheels and tyres BMC specced on the Kaius are on the money for the bike’s intended use too. Pirelli’s Gravel H tyres roll quickly but have just enough of a profile off-centre to extend their grip while cornering off-road.

Zipp’s 303 Firecrest wheels are a high-performance all-rounder. I’d suggest their 40mm rim depth to be a little deep for more technical gravel, where a truly low-profile rim might offer a little more compliance, but for light gravel and road riding they are brilliant.

Their claimed weight is around 1,400g, making them very light, but their 25mm internal rim width makes them wide enough to support wider road tyres and racy gravel tyres. What’s more, among similarly specced competition they seem like good value for money too.

SRAM’s Red eTap AXS XPLR groupset takes care of the Kaius’s shifting and braking, and there isn’t much more to say about it that hasn’t already been said.

The 10-44 12-speed cassette offers good gearing range without huge jumps in between gears, while the derailleur shunts the chain around them precisely no matter how rough the chain, courtesy of its neat Orbit Fluid Damper, a pseudo-clutch mechanism. Braking was powerful and quiet, if not feel quite as nicely progressive as Campagnolo’s Ekar callipers.

BMC Kaius 01 One geometry and sizing

The Kaius’s headline-grabbing move to 36cm bars was an attempt to improve aerodynamic efficiency, but simply just narrowing the bars can actually have the opposite effect.

It effectively reduces reach, which can cause the rider to sit up taller, so this is where the Teammachine’s influence starts to wane and the URS’s features start to dominate, namely in the construction of the Kaius’ geometry.

From the bottom bracket forward, the Kaius is stretched out, using a long top tube to keep the rider low. While it doesn’t go as far as the URS, the Kaius’ handling geometry is still relaxed for a bike of its racy remit.

The bike’s 72-degree head tube angle combines with notably little fork offset (45mm), to create 68mm trail with 40mm tyres. It’s less than the URS but definitely longer than other similarly positioned bikes.

A shorter stem attempts to combine with the narrower bars to reclaim a little responsiveness at the front end, which is aided by a comparatively tidy 420mm rear centre.

The bike’s combination of features makes for a fascinating design on paper and translates into a very particular feel out on a ride.

Riding the BMC Kaius 01 One

On a typical gravel bike I’m looking to get off-road at the earliest opportunity but the Teammachine-derived features on the Kaius made it unusually fun to spend extra time getting to bridleways or linking trails with sections of road.

The bike’s short chainstays and oversize bottom bracket junction contributed to making the bike feel stiff under effort, while the fast-rolling Pirelli tyres, light Zipp wheels and compact cockpit helped to create a fast ride feel.

The bike’s handling was the only reminder I wasn’t on a pure road bike. With the front end being relaxed, the steering generally felt sedate.

Paradoxically, perhaps due to the compact cockpit and/or small fork rake, there was slight evidence of wheel flop at lower speeds or when climbing, which is the sensation that the front wheel wants to wander offline rather than stay centred.

Transitioning on to even the lightest gravel caused BMC’s geometry choice in the Kaius to click into place though. The subtle increase in technicality quelled any handling foibles.

The decrease in grip that makes more road-focussed gravel bikes feel nervy tightened the Kaius handling enough to make it feel confident.

Rougher surfaces only suited the bike’s characteristics more, to the extent that its handling meaningfully extended the capability of the Pirelli tyres.

Thanks to the bike’s stability and balance I was able to stay upright on muddy, off-camber trails where the comparatively slick tread of the Pirellis would usually be well out of their depth.

The squishy back end caused by the compact frame and long, D-shaped seat post worked wonders to help keep the otherwise rigid bike comfortable and under control too.

BMC Kaius 01 One verdict

I applaud BMC for taking yet another original approach for gravel that is just as successful as its first attempt, but the Kaius leaves me with two sticking points.

The first is superficial: white is not the colour for a gravel bike. It looks great in a showroom, but that pristine sheen can never be recaptured once ridden, unless you spend more time cleaning than you do riding.

The second is sadly not an issue unique to BMC, but unless money isn’t a concern, I can’t see the justification in spending five figures on a bike destined for a hard life.

Prospective customers would do well to consider the Kaius 01 Three that BMC sensibly offers, which sacrifices on build (affecting weight but ostensibly nothing else, performance-wise) to halve the cost of the Kaius 01 One.

Nonetheless, as an aggressive gravel bike with almost no compromise in any area, the Kaius 01 One is right up there. After Pauline Ferrand-Prevot won the inaugural Gravel World Championships on a Kaius, its design is already well on the way to being proven in a far more credible manner than my humble ride report too.

• Buy the BMC Kaius 01 One now from bmc-switzerland.com (£11,350)

BMC Kaius 01 One specs

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Image credit: Lizzie Crabb