There’s a 22mm (later became 34mm on later forks) spring on the cartridge rod known as the ‘top out spring’ (a photo on the left shows an enormous 75mm Terry Hay T-O spring) for when you are in mid-air and the forks want to fall apart! They cushion the bang! When hitting a bump, the cartridge rod assembly goes down into the oil. The fork oil is either forced down through the BV or up through the ‘check-plate/MV’ but it goes through the check-plate three times as quickly. When the forks rebound the CP lets the oil back down through, then through the piston and then past the rebound stack.