Jasper Janssen said:
Which is how far? You need both the seat angle and the seattube length to
do that calculation (actually, you need seattube length plus exposed
seatpost length for the exact number). Assuming a 50 cm seat tube, the
difference that the 1 degree of angle makes is about 500 * (sin 1) mm, aka
8.7 mm. So your seatpost lug will be nearly a cm further forward, by the
time you're at the saddle it'll probably be a bit more than a cm, and you
should probably go to a 105 stem to compensate.
Actually, the exposed seatpost does not matter (since he has already
located his saddle), only the ctc seattube length. An important factor
is whether or not the two bikes have horizontal or sloping toptubes...
I'm assuming they are both horizontal with 55cm ctc seattubes (just
because that is pretty average)... and if we wanted to be precise (for
no good reason) we'd have to know a bunch of other things, too... so
I'll assume that the following are all the same between the two bikes;
bottom bracket height, headtube length, headset stack height, fork
length, stem clamp height above the headset, stem angle, and the
handlebar reach (can you tell I recently wrote a spreadsheet to deal
with all this stuff?).
Difference = 55*(sin(17)-sin(16)) = .92cm which means you'd like a 1cm
shorter stem (105cm) if you wanted it to be the same as before. But
like Ken said, 1cm on the reach is not much... maybe you'd like it a
bit longer than before?
