Motorcycle Shock Shaft Dust Wipers

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).

Hard outer dirt wipers scrape away grit & corrosive mud preventing it from grinding & pitting the chrome damping rod of your rear shocks - protecting the softer inner oil seals from damage and eventual leaking.