after having one bike stolen.. the only 2 things i reccomend are a big chain and a solod ground anchor.... and a shot gun......
but serioulsy,, if they cant pick it up and walk off withit , that eliminates the oppertunistic thief...
as for the rfessionals.. well... we all know NOTHING will stop them if they want it that bad..... (cept maybee the shotgun if u catch em at it)
hth and welcome..
