My sister pulled her old late 80's - early 90's Hardrock out of the attic and asked me what a Shark tooth is. She said it is mounted on her frame near the downtube or chainstay (one of those) and never really noticed it. She is one of those who got the bike as a gift, then put it away for years and years. Tried to search the forums, but all I got was the "shark tooth" wear of chainrings. So....who knows?
1991 Trek 930, 2005 Bianchi Eros, 2006 Nashbar "X," IRO Rob Roy
i think she means a "Shark Fin." it was a accessory from Shimano that claimed to reduce or eliminate chainsuck. it mounted on the drive side chainstay, with a "fin" near the crank and a flat part that ran along the stay. i've got one somewhere (had it on my Trek for years). it didn't work for s**t to prevent chainsuck, but it was a pretty neat looking chainstay protector. i doubt they've been made in years.
you can see one in this picture:
thanks to First Flight Bikes for the pic.
now there was a "Shark Tooth" accessory also - it mounted on the U-brake as an anti-jam device. but i've never seen one, and she'd have to flip the bike over to see it.