Fork seals are the reinforced rubber or composite seals which fit tightly over the ends of the fixed fork tubes, and through which the inner fork tubes slide. Their purpose is to locate the slider tubes while at the same time ensuring an oil-tight seal. Over a long period they can deteriorate and start to leak fork oil, although the more normal cause of leakage is corrosion or damage to a fork tube which in turn damages the seal.

Fork seals are identified by ID (internal diameter of seal) x OD (outer diameter of seal) x depth in mm. Generally the size is embossed into the seal (though very small!)

Seals should always be changed whenever any sign of fork oil leakage is noticeable, or whenever fork tubes are changed.

Dust seals, also sometimes called wiper seals, cover and protect the main seals. Note that they are not fitted to all bikes, but are especially important on off-road machines. Some bikes have expandable fork boots to keep dirt away from the fork seals.