The first measurements we need to do before
purchasing a bicycle is to measure the crotch. It
is not so important because this influences the proper sizing of the bike. If
we make a mistake then trying to regulate all other distances will arrive at a
dead end. Barefoot
standing upright with his back resting against the wall , head facing forward
and your heels touching the wall, and the distance between the legs is about
15cm .We take a hard book and place it between our legs touching the soft area such as the saddle when we're on the bike. When you get to this point upper note with a pencil point on the wall. This metric shows the height of the crotch is multiplied by some coefficients gives us the right size bike and the correct seat height .