Using Nylon vs. Silicone Washer on Bafang BBSHD BBS01 Mid drive E-bike Motor Assembly
Nylon melts at a low temperature, but probably not gonna happen there. That is a worthless, free guess for you. The bearing looks to my unschooled eyes like a ball thrust bearing?  The "silicone" washer would be an aid to prevent ingress of dirt and egress of lubricant.  (PT Barnum famously led dalliers out of his mid-1800s New York Museum via a street door labeled, 'this way to the Egress,') ha ha!  Well, that Bafang sure has served you well. I vote that the slightly damaged old seal should remain on duty.  It is a known success and its job is not vital. It is a trained seal. I mean experienced seal. If it were a trained seal it would be playing toot horns in Barnum's American Museum.  


  
    
      
        
          ------------> this    way    to    the   Egress
        
      
    
  


On second thought, it is not a seal, is it?  It's a deformable washer that smashes between a bearing adjustment nut and its locking nut. I don't understand its purpose but I don't know much.  That the motor has lasted so long is a great testament to the designers' skill.  Too bad, we can't ask them who really know.  Again, I would not replace it at all.  Nylon is low temperature, slippery and deforms (flows away) from pressure. IF that is a lock nut system, a nylon washer between the adjuster and the jam nut would not be a good idea.  The original "silicone" washer will serve just fine again, remains my opinion.