How do I compare the effective setback of a seatpost?

At first glance, it is quite difficult to directly compare the actual setback of a seatpost. With a simple template however, this is quite simple. Just print (without any scaling) the template, cut it out and fold at the dashed lines.

Now, as in the diagram, place the template on the front edge of the seatpost tube and slide upwards until the two “sensors” are level with the seat rails. The P6 from 2011 onwards has the front collision point at the exact position of the two sensors and hence the template can be used as a “P6 reference template”.

Similarly the forward most saddle position can be determined. The rear collision point of the saddle rail and the P6 top clamp is approx. 30mm rearward of this position.

Seatpost reference template as PDF