1.- From the center of the bottom bracket to the top of the vertical pipe near the saddle (centre to top or CT) and
2.- From the center of the bottom bracket to the point where the center of the horizontal tube intersects the vertical (centre to centre or CC). This means that when the distance in the CT is 56cm for instance, the distance CC is about 53.3 - 54cm i.e. (1-1.5 cm less).
The above bike - technical terminologies we call them like what they mean - over (CT) or mean - under (CC).
To decide which one is the right length bicycle
must multiply the length of the crotch of over 0.67. If for instance, one
has crotch 85cm: 85 x 0.67 = 57cm (CT).
The length of the vertical tube (CT)
must be 57cm.
The American biker Greg Lemond winner of the Tour de France (three years), in his book
mentions that calculates the distance from CC and multiplied by 0.65 which
leads to approximately the same result. Also tall cyclists may feel
uncomfortable in accordance with these types. In such cases it may be purchased
bicycle that is 25-28mm shorter than the length of the crotch, risking relative
to the geometry.
For
mountain bikes or bikes type slopping the frame can be about 10-12cm smaller than the classical geometry road
bikes. For example a cyclist who needs a
55cm road bike will need a mountain bike
43-45cm. Because there are measurements in inches you need bike 17΄΄-18΄΄.
In many cases the mountain bikes are better to
purchase based on the horizontal tube (top tube) and because it has minimal
impact on the corners of the foot utility of a frame 17΄΄ or 19΄΄. In such an
instance, however, the difference in horizontal pipes can reach the one thus
requiring significant changes in other parts of the bicycle for instance, the
steering neck and at that point caution. The above measurements can be
partially corrected with measurements of saddle, steering wheel etc.
but they can΄t fix big
mistakes because trying to adjust one part missing the other.