Hmm just weighed it, my scales are out or it's 21kg without spring collars. Sort of annoying.... (I weighed 5kg, 5kg weighed 5kg, tried with 10kg, then added bar and got 26kg and 31kg both times..)
u use a test weight? If all your weights are spot on and the bar is a kg out you know its the bar
Use the heavier weights too cause the heavier it is the worse the inaccuracy will be if it's the scale