gravel bike frame geometry S-PARTS Titanium Alloy Gravel Bike Frame

CROSS CONTROL SYSTEM 2.0

This is the crowning design that we have meticulously developed and finally achieved for mass production. Years ago, when S-PARTS began its custom titanium frame business, we insisted on using a design where the seat stays connect to the top tube, which we termed "CROSS CONTROL" technology. This method effectively uses the passive deformation of metal to absorb road bumps in non-suspension frames. However, due to early technological limitations, we had to conservatively weld the connection between the seat stays and the seat tube. While this ensured the frame's strength, it significantly compromised the original goal of vertical shock absorption, which was undoubtedly frustrating.

For years, this issue has been on our minds, and the S-PARTS team never gave up on finding the optimal solution. In 2023, we introduced new hydraulic bending equipment and internationally advanced calibration and testing instruments. With these resources, we ventured into more daring tube and profile designs, using 3D software to simulate a completely disconnected structure between the seat stays and the seat tube, which we successfully achieved in simulations. This led to the creation of the "CROSS CONTROL 2.0" system we have today.

We chose slimmer seat stays, internally hydroformed to maintain support strength while providing ample clearance. This design allows for controlled physical deformation on rough roads, achieving the intended shock absorption function. To increase the contact area and vertical support strength at the weld points between the stays and the top tube, we used a special vertical pressing mold at both ends of the top tube. This created two elliptical cross-sections—one horizontal at the head tube and one vertical at the seat tube—achieving both aesthetic and functional benefits.

ASYMMETRIC REAR FORK

Traditional metal frames, when requiring compatibility with both large chainrings and wide tires, usually compress the drive-side chainstay to form a dent. This is an unavoidable compromise that inevitably damages the original tube wall structure, resulting in a loss of strength.

S-PARTS designed a connector CNC-carved from a single piece of titanium alloy plate, perfectly solving this issue in multiple ways:

1. The solid titanium alloy connector provides higher connection strength than tube materials, ensuring drive-side pedaling rigidity.
2. The 6mm wide plate offers considerable installation space for both tires and chainrings, allowing the GRAVEL frame to accommodate tires up to 42c and chainrings up to 48t.
3. The asymmetric recessed design also provides more chain movement space, significantly reducing the chance of chain-to-chainstay collisions during extreme bumps.

Internal cable routing / CNC rear dropout / UDH derailleur hanger / T47 bottom bracket

The frame features a 52mm integrated headset with uniform diameter, supporting ACR and DCR systems for fully internal cable routing with both integrated and non-integrated handlebars.

The fully CNC-machined flat mount brake caliper installation base ensures high strength and precise mounting holes for quick and accurate setup, delivering sharp and powerful braking performance.

The entire series is equipped with the UDH direct mount dropout system, compatible with nearly all rear derailleurs on the market.

The T47 threaded bottom bracket, standard across the series, is the optimal solution for metal frames, offering excellent stability, pedaling stiffness, and minimal noise risk. For 24mm spindle specifications, it supports a fully hidden brake hose routing solution within the bottom bracket shell.

Frame Assembly Guidelines

Head Tube: Use upper and lower 52mm integrated bearing headsets, ensuring compatibility with ACR or DCR system internal cable routing.

Fork: Optimal fork specifications for this frame are a length range of 389-400mm (excluding suspension forks), an offset range of 48-55mm, and a maximum tire clearance >42c.

Bottom Bracket and Crankset: The frame's bottom bracket shell width is 68mm and requires a T47 external bearing bottom bracket. The specific model depends on the crankset used; please consult your retailer or S-PARTS official customer service. The frame supports a maximum chainring size of 48T.

Shifting and Braking: The frame is compatible with DI2, AXS electronic shifting systems, and similar electronic shifting products (not compatible with any mechanical shifting systems). The frame only supports FLATMOUNT disc brake systems.

Seat Post: Only compatible with 27.2mm diameter round seat posts.

Wheelset: Only compatible with 700c wheel specifications and 12mm thru-axle road wheelsets.

Gravel frame fatigue test report - Chinese