Forgive my ignorance since I haven't seen them in person, so I'm not exactly sure what they are, castle nuts, decorative covers, etc....I've seen some pics of bikes that look like they have spikes coming off their axles. What are they, and where do I get 'em?

 

They usually areaxle covers butthere are avariety of different sizes for your bike for different area's

 

Try www.perseperformance.com