gravel bike bmc BMC Kaius 01 Four Bike

BMC has been building bikes in Grenchen, Switzerland since 1986, and the BMC Kaius 01 Four Bike is where that engineering tradition meets the demands of modern gravel racing. The Kaius 01 is BMC's performance gravel platform — built for riders who race gravel, not just ride it — and the Four is the entry point into that platform, pairing the Kaius 01 carbon frame and fork with a full SRAM Rival XPLR AXS build at $5,199.

The frame and fork are built from Kaius 01 Premium Carbon shaped around three integrated technologies. Aerocore is BMC's aero carbon design, derived from the Teammachine R 01 road race bike — tube profiles and transitions engineered to reduce drag at the speeds modern gravel racing produces, where average speeds at major events often push toward 35 kph. ICS (Integrated Cockpit System) routes cables and hydraulic hoses internally through the stem and headtube, eliminating external housing and reinforcing the frame's aerodynamic intent. The third element is TCC Race compliance — specific zones of the frame are tuned to flex vertically while maintaining lateral stiffness, absorbing trail chatter before it reaches the rider and keeping tires planted through rough sections. BMC's logic is direct: planted tires maintain traction, and traction is speed. The D-shaped carbon seatpost adds compliance from the saddle down and is compatible with BMC's D-Fender for year-round use. The frame runs 12mm thru-axles front and rear and uses a UDH (Universal Derailleur Hanger) for broad service compatibility.

The drivetrain is SRAM Rival XPLR AXS, a groupset built specifically for gravel riding. The XPLR designation reflects its gravel-first design: 1x13 with a 42t chainring and a 10–46 cassette that covers steep climbs and flat-road pacing without requiring a front derailleur. Wireless operation eliminates cables from the shift path entirely, keeping maintenance low and the cockpit in line with the Kaius 01's integration intent. Braking comes from SRAM Rival AXS hydraulic disc calipers on SRAM Paceline Centerlock 160mm rotors front and rear. The BMC RSM 01 integrated stem pairs with a BMC HB D4 03 alloy handlebar — 125mm drop, 70mm reach, and 12 degrees of flare. That flare angle widens the hand position in the drops, improving stability and control on unpredictable surfaces where narrow drops become hard to hold.

BMC equips the Kaius 01 Four with its own CG 40 carbon wheels — 40mm wide, tubeless-ready rims designed around the gravel platform. The width provides a stable foundation for gravel-specific tire volumes without excess weight, and the tubeless-ready bed works directly with the included Pirelli Cinturato Gravel H tires in 700x40. The Cinturato Gravel H is Pirelli's fast-rolling hardpack tubeless option: a file-tread center for low rolling resistance on packed surfaces, side knobs for cornering on loose terrain. At 40mm, the setup sits at an efficient balance point for mixed conditions, and tire clearance extends to approximately 44mm for riders who want more volume in wet or technical riding. The saddle is a Fizik Vento Argo X5 in 140mm — a short-nosed design intended to allow more hip movement in the forward position gravel racing demands. Carbon bottle cages from BMC's Aerocore line complete the build, keeping the frame's visual language consistent.

The Kaius 01 Four is built for gravel racing, and the spec reflects that at every touchpoint: the aero-tuned carbon frame, wireless wide-range drivetrain, integrated cockpit, and carbon wheels. The Four build puts you on the full Kaius 01 platform — the same frame and fork used across the entire 01 lineup — with SRAM Rival XPLR AXS rather than the higher-tier Red or Force builds above it. The frame is where the meaningful investment is, and it doesn't change. Available in Black/Neon Red across six sizes from 47cm to 61cm. Pedals are not included.