Rotor offers two axles for our crankset builders: the Standard Axle and the Offset Axle. The Standard Axle offers provides a 43.5mm chainline while the Offset Axle provides a 46mm chainline.
When choosing between a 43.5mm chainline or a 46mm chainline for a road or gravel bike, several factors come into play. The chainline refers to the distance between the bike's centerline and the centerline of the chainring(s). It plays a crucial role in determining the drivetrain's efficiency, shifting performance, and overall bike handling. Here's a brief explanation of why one might choose either option:
A 43.5mm chainline is typically used in road and gravel bikes with traditional double chainring setups. This chainline places the chainrings closer to the bike's centerline, resulting in a narrower overall Q-factor (the distance between the pedals). A narrower Q-factor can provide benefits such as improved pedaling efficiency, reduced strain on the knees, and a more natural pedaling motion. It may also contribute to better aerodynamics and a more streamlined appearance.
A 46mm chainline is commonly employed in gravel bikes with single chainring setups or bikes using the 2x GRX/AXS gravel groupsets. This chainline moves the chainring(s) slightly outward, away from the bike's centerline. The primary advantage of a wider chainline is improved tire clearance. With larger tire sizes becoming popular in gravel riding, a wider chainline ensures that the chainrings do not come too close to the tire, reducing the risk of interference or chainring contact when riding on uneven surfaces. Additionally, a wider chainline can enhance chain retention and stability in rough conditions, reducing the chances of chain drops or derailments.
Ultimately, the choice between a 43.5mm chainline and a 46mm chainline depends on the specific frame/drivetrain requirements and preferences of the rider. Considerations such as riding style, terrain, preferred gear ratios, tire clearance, and the type of drivetrain (double or 1x) all play a role in determining the optimal chainline for a road or gravel bike.