manufacturers install setback seatposts on new
bikes to extend the range of bike fit positions possible.
This is usually to
address taller riders who, being on the edge of two bike
sizes, prefer to ride a smaller, more responsive
Ultimately, during the bike fitting process, the position of the saddle on the seatpost
is determined by what we call the "power" portion
of the bike fit. During this part of the bike fit, your
position in the saddle (height and forward/aft) is
determined, so you deliver the most power, most
efficiently and while biomechanically neutral for injury
More often than not,
we find that a 0 offset seatpost (AKA straight) is
better suited during the fit process.
If the bike is the
appropriate size for a rider's body, it's very likely
that he/she will fit on a 0 offset seat post, and the
saddle rails will be positioned between 1/3 and 1/2 of
the max range.
Especially true for mountain bikes (but also road), it's
advisable to avoid a saddle pushed all
the way forward or back. This maxes out the
rail flexibility and, potentially, begins the stress cycle
of material fatigue that can lead to
catastrophic failure of the saddle rails. it's
wiser to use a seatpost that places the saddle as close
as possible to near the
middle of the rails.
and track bikes are the exception.
Special cases also.