TECH Q&A
SITTING PRETTY
What’s the difference between the effective seat tube angle and the seat tube angle of a bike? Are there two names for the same thing? I see both used in various places.
Stan, via email
While the term ‘seat tube angle’ is often used interchangeably, these two measurements do differ. The seat tube angle is just that – the angle from horizontal of the seat tube itself, towards the top, and thus the angle of the seatpost. A more useful measurement is the effective seat tube angle – the angle of a line drawn from the centre of the bottom bracket to the centre of the saddle clamp on the seatpost. On nearly every full-suspension bike, and some hardtails, too, this will be steeper than the seat tube angle, because seat tubes often start forward of
