3T Ultra GRX Bike

The 3T Ultra GRX Bike is 3T's aerodynamic all-terrain gravel platform — a complete bike built around the premise that speed on mixed surfaces comes from optimizing the whole system around the tire, not in spite of it. At $4,399, it pairs 3T's REALFAST aero carbon frame with a Shimano GRX 12-speed 1x drivetrain, Fulcrum Rapid Red 900 wheels, and Pirelli Cinturato Gravel tires in a build designed to go fast wherever the road runs out.

REALFAST Aerodynamics

The Ultra's defining engineering idea is that the frame's aerodynamics were designed around the tire's actual dimensions, not around a narrow road profile. Using hundreds of real-world tire measurements, 3T developed REALFAST aerodynamics — a frame geometry and tube shaping approach that manages airflow around the real outer diameter and width of the tire rather than working against it. The most visible expression of this is the downtube, which measures 60mm wide and flares outward to 75mm as it approaches the bottom bracket. This shape shields the water bottle from direct airflow and optimizes the air transition from the downtube and tire into the bottom bracket area, reducing drag at the point where a wide tire would normally create a significant aerodynamic penalty.

The frame is built from a unidirectional pre-preg carbon layup using a high-modulus/high-strength performance blend. The seat tube is aero-profiled and mates with a 3T carbon 27.2mm round seatpost — a diameter deliberately chosen for its natural compliance and broad compatibility with dropper and suspension posts. Double-drop chainstays open clearance for wide tires and larger cranks simultaneously, handling a practical tradeoff that most gravel frames have to make less gracefully. A threaded bottom bracket and integrated fender mounts add everyday usability. The fork is the 3T Fango RaceMax Integrale with a compact minimalist crown, shaped for aerodynamic efficiency while maintaining the compliance character of the platform.

Tire Versatility

This build ships with Pirelli Cinturato Gravel M tires in 700x40mm — a well-regarded tubeless gravel tire that covers the majority of mixed-terrain riding at the faster end of the gravel spectrum. The frame's actual design range is considerably broader: the Ultra accommodates 55-61mm tires on 650b wheels, which opens up looser, more demanding terrain without requiring a different bike. The shift from 700c to 650b with wider rubber is a meaningful change in capability, and the Ultra is built to support both configurations.

Shimano GRX 1x12 Build

The drivetrain is built around Shimano's GRX platform, which is engineered specifically for gravel and off-road conditions. The Shimano GRX RX822 rear derailleur handles a 12-speed 10-51T Shimano Deore cassette — wide enough to make the 40T chainring workable on sustained climbs and fast enough on flat or downhill terrain. The Shimano GRX RX610 levers provide clean, reliable shifting, and the Shimano GRX RX400 hydraulic disc brakes with 160mm RT64 rotors deliver strong, consistent stopping power in all conditions. Running 1x simplifies the cockpit and removes a mechanical point of failure on terrain where shifting under load happens constantly.

The cockpit is 3T's own throughout: a 3T Apto Stealth stem and 3T Superghiaia LTD handlebar, the latter a flared drop bar designed for off-road riding where the outward splay of the drops provides stability and leverage on rough terrain. Fulcrum Rapid Red 900 wheels carry the bike, with a Fizik Terra Alpaca saddle and 3T Prendo Tough bar tape completing the build. Pedals are not included.

Geometry and Sizing

The Ultra is available in six sizes from 48 through 61cm. Head tube angles range from 68.5° at size 48 to 72.5° at sizes 58 and 61 — the smaller sizes run notably slack geometry, a deliberate choice for stability on loose terrain, while larger sizes handle more like a fast road-gravel bike. Seat tube angle holds at 74° across all sizes, and chainstay length is consistent at 419mm throughout the range. Stack spans 520mm to 632mm; reach runs 351mm to 399mm.