sorry pedro i had to go and service something else for 30 mins
the effect of not enough rear spring preload on the bike is that the front steering angles( rake ) are increased ie like a chopper. this is because the rear of the bike squats to much with your weight acting on it.
to counteract this we ad more spring preload to the shock absorber ,this then pushes up/supports the rear of the bike against the added weight of the rider (the veriable in this equation) ................................
hic !!!!!! im drunk its time for bed