The factory equipped Solo machines with upper and lower buffer springs, except for the 1946-49 model years which only had lower buffer springs. These short buffer springs have no suspenion function but solely prevent bottoming out of the fork. They have a C-shaped arc against rattling.

WLC (Canadian Army), Servi-car and Big Twins with sidecars came with lower inner cushion springs to compensate for the higher weight or severe duty.