That felt is intended to be a debris and dust barrier to keep road grit, mud, etc. away from the sealing lip. Rubber sealing lips don't last long in dirty environments. Some of the newer-design seals have a second lip outboard of the one with the garter spring to try to accomplish the same thing.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!