Good question. Maybe one of our SFI certified safety officials can step up and answer the question.
Snell is the adopted safety testing & approval system for headgear. There are different Snell ratings for automotive AND motorcycle helmets. I think its only updated every five years so Snell 95 is the latest.
SFI is the adopted safety standards for performance equipment adopted by the major drag racing sanctioning bodies. I'm not sure if SFI is adopted by the road racing bodies. But there are different standards for the different components. For example, SFI 18.1 pertains to harmonic balancers and it defines not only the test process but also the acceptance criteria. I'm not sure who/what you'd contact to actually get ahold of the various SFI standards.
Hope I'm not passing along any misinformation. I really know very little about the standards other than its what's called for in the rulebooks.
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Jeff Chambers
T/S #4
12.40 Seconds/109.5 MPH
http://www.kellnet.com/chambers/default.htm