hi,
if they want it they will get it, even if you have it locked on (mine has a bike chain and padlock on it).
whats to stop them jacking up and taking of one thats not the spare, actually on the trailer (I chain thru the wheel and chassis when we pull up in an attempt to stop th etheft of the whole trailer,
whatever you do you will only keep the honest theive away..........
cheers
Garry