Motorcycle Shock Shaft Oil Seals

Motorbike shocks use a damping shaft that slides inside the main shock absorber body. To keep all the oil and nitrogen pressure inside that casing there is a lower seal head assembly between the two.

Rear dampers have multiple defences in there - an oil seal held deep inside, a dust wiper on the outside, a rod bushing to keep it sliding concentrically, a rubber o-ring sealing the outer diameter and a rebound top out bumper facing inwards. That bump stop can be a rubber ring or a small steel coil spring, and it makes sure no damage happens if the shock piston bumps into the bottom case (like when you jump the bike).

Soft viton rubber inner suspension fluid seals stop leaks with a minimum of friction, preventing dust sticking to the chrome damping rod of your rear shocks in the first place.