bicycle frame dimensions

Seat Angle is the angle that the seat tube axis makes with the horizontal. Seat angle is measured clock-wise from the ground when viewed from the right side as shown above.

For unconventional frame geometry, it may also be useful to display the effective seat tube angle or the angle from BB to top of seat tube.

Head Angle is the angle that the steering axis makes with the horizontal. Head angle is measured clock-wise from the ground when viewed from the right side as shown above.

In BikeCAD, seat tube length can be input and displayed in two ways. The first measurement is from the center of the bottom bracket to the center of where the seat tube and top tube connect. This measurement is called Seat tube length (c-c). The second measurement is from the center of the bottom bracket to the top of the seat tube. This measurement is called Seat tube length (c-t).

Stack is the vertical distance from the center of the bottom bracket to the top of the head tube. The horizontal counterpart to Stack is Reach.

Reach is the horizontal distance from the center of the bottom bracket to the top of the head tube. The vertical counterpart to Reach is Stack.