boost spacing gravel bike 3T Ultra Boost Apex Eagle Gravel eBike

The 3T Ultra Boost Apex Eagle Bike starts from a different premise than most gravel eBikes. Rather than adapting a mountain bike platform for drop bars, 3T took the Exploro Ultra — their purpose-built aero gravel frame — and integrated the Mahle X20 motor system inside the same carbon chassis. The geometry, tube profiles, and steering feel of the original Ultra carry over unchanged. What's new is what's hidden: a motor and 350Wh battery that expand where the bike can take you without changing how it rides when you don't need the assistance.

REALFAST Aerodynamics

3T engineered the Exploro Ultra around what they call REALFAST aerodynamics — actual tire measurements, not label widths, dictating frame shape. The downtube runs 75mm wide at its base to fully shield the water bottle and redirect turbulent air coming off the front wheel, then narrows to 60mm at the neck to catch airflow exiting the tire. A close-fitting rear wheel cutout minimizes the gap between tire and seat tube. Double-drop chainstays serve two purposes: better crank and tire clearance on the drive side, and a stiffer, lighter structure behind the bottom bracket where both stays drop. The fork uses a pure-road crown length — 25mm shorter than a typical gravel fork — which tightens the steering geometry, reduces weight, and improves front-end stiffness without sacrificing ride character on mixed terrain. The aero seat tube is designed around a 27.2mm round post and accepts both dropper and suspension seatposts, options that most aero frames close off entirely.

Mahle X20: Integrated and Unobtrusive

The Mahle X20 system delivers 55Nm of torque through an integrated setup designed to feel like an extension of your effort. Three power modes are configured specifically for the Ultra Boost, and a fourth is fully customizable through the MySmartBike app. The system communicates over Bluetooth and ANT+, making it compatible with Garmin head units without additional sensors. On the 350Wh integrated battery, 3T's data indicates that a rider under 75kg can cover more than 150km with 2,000m of climbing on a mix of gravel and pavement — enough for a full day in the hills without conserving power on the climbs. For longer objectives, a separate 173Wh Mahle battery extender (1.1kg) mounts to the seat tube's bottle cage and extends total range by roughly 50%. A bike that already goes far enough for most days, with a credible answer for the days it doesn't.

Apex Eagle: Wide Range, Proven Gearing

The Apex Eagle build pairs SRAM's Apex Eagle rear derailleur with a 40T chainring and an 11-50 NX cassette across 12 speeds. The ratio spread is deliberately wide — useful on sustained climbs, loose surfaces, and anything in between where tighter road gearing would leave you spinning out or grinding. SRAM Apex hydraulic disc brakes with 160mm rotors handle stopping with consistency in wet and dry conditions alike, and 3T's direct-mount brake standard eliminates the adaptors most frames require for that rotor size. The cockpit is 3T throughout: an Apto Stealth stem and Superghiaia LTD flared drop bar keep the rider in a lower, faster position than the flat-bar Urban version, with enough flare at the drops for confident control on rough descents. Rody alloy wheels and Pirelli Cinturato Adventure 700x45 tires handle the surface variety the Ultra Boost is built for — capable on loose dirt, smooth on gravel, honest enough on tarmac that the road sections between trail heads don't feel like a penalty.

The Apex Eagle is the entry point into the Ultra Boost lineup, and the build that prioritizes range, mechanical simplicity, and durability over electronic shifting or carbon wheels. Available in six sizes from 48 to 61cm in Black/White, it fits a wide range of riders and puts the full capability of the Exploro Ultra platform within reach — with enough motor assistance to push deeper into the day, pace with a faster group on mixed terrain, or take the detour that would otherwise be out of reach.