4
The best place in the Bay Area to get a helmet is:
http://www.bellmotorsports.com/
or
http://www.helmetcity.com/page/HC/CTGY/AH
in Oakland.... They have every size in stock. You need to try these things on as the sizes really don't mean as much as they used to. I cannot fit into any helmet made bt Bell regardless of size due to Snell 2000 padding in the lower shell. I did have Bell Snell 85 and 90 helmets which fit and switched to Simpson for 95 and 2000. Oakland is not that far... make sure you get an SA2000 helmet for car stuff and not the cheaper nylon lining.
Steve