For
this you will need to have a plumb line - a string (about 24")
with a weight on the end and a helper.
Pedal for a minute or two. Your helper should pay attention
to the angle that your foot is in (heel up, heel down, neutral)
when it hits the 3 o'clock position. Now placing your pedal
in the 3 o'clock position (holding your foot at the correct
angle) you will drop the plumb line from your knee noting the
relative fore / aft distance from the plumb line to the pedal
axle.
If you are 5'2" to 5'8" with average shoe size and pedal at
a moderate rpm, then the line should pass through the pedal
axle. If you are taller, or have proportionately larger feet
or favour pushing larger gears at a slower cadence, then the
line should fall slightly behind the pedal axle.
Conversely, if you are shorter or have smaller feet or tend
to spin at higher rpm, then the line should fall through or
ever so slightly in front of the spindle. It's all proportionate,
... a 6 footer, with size 10 (44) shoes that pedal with a moderate
cadence, may have an ideal knee position about 15mm behind the
pedal.
In mountain biking, the tendency is to pedal with a somewhat
slower cadence so generally people are set up with the line
slightly behind (5mm) the axle ... and up to 2cm behind the
axle for very tall cyclists. Ultimately, you will fine-tune
this position by making small adjustments and trying them out
for a few rides.
Hopefully
you will be able to adjust your fore / aft position sufficiently
by sliding your saddle on its rails. If you cannot move the
saddle enough (and you already own your bike), then a change
of seatpost may offer the added bit you need. Many seatposts
are on the market and you will notice different styles and locations
of the clamp. Some are along the centre line of the seatpost
while others, in varying degrees are offset to the front or
to the rear of the post. If you are buying a new post (or a
new bike) it is always desirable to have room for adjustment
both fore and aft if possible.
This is where the seat tube angle of the frame comes in. Ideally
the saddle should both be in the correct fore / aft position
for pedalling and the saddle should be clamped in the middle
of the rail travel, so you will always have room for adjustments
either way. A frame with a seat tube angle of 73 degrees will
accommodate better than 80% of cyclists along with proper selection
of the seat post.
Once the fore / aft has been set, you should re-check the saddle
height. If you needed to move the saddle back, you will probably
need to lower the saddle slightly, if brought forward, you will
need to raise the saddle.
A Serotta Size-Cycle and appropriately trained technician is
available in the form of James Huggins, of Rock 'n' Road Cycles.
If you like what you hear in this section please drop
us and e-mail with your details and we will be happy to
pass them on to James. James also imports the complete range
of Serotta bikes from the USA so again if you are interested
in further details drop
us a note and we'll do the necessary.
