I dont know the size but you "should" be able to take it to any auto parts store worth a damn and they should be able to tell you what size and thread pitch it is. Most all of them have a bolt/thread gauges right there at the counter. Heck you could probably buy one for a few bucks and see what size it is yourself. Its probably a fine thread SAE bolt, and its probably a full thread bolt that does not have a shoulder or something. My guess is its like a 1/2-20, 9/16-18 or something. Being a seat bolt, it could be hardened but I dont know that. May end up having to order it from a bolt store.
Last edited by redbandit98; 12-21-2011 at 05:22 PM.