Lookout Dr resident Jim Robbie discovered the tractor wheel in his front garden yesterday morning, next to where he had been digging the previous day.
"The people who would do this - throw a tractor tyre down the hill - are just idiots. There's always people around here so the chance of hitting someone is high," he said.
The area between the Manuherikia River and the clock on the hill was popular with walkers, runners and cyclists, during the day and at night.
Mr Robbie had been digging in his garden until 5pm on Sunday so the wheel was hurled down sometime between then and yesterday morning.
"It's pretty heavy, so you'd need a ute or trailer to transport it and, because of the size of it, you'd probably need a couple of people to lift it," Constable Lance Davies said.
Central Otago sub-area police supervisor Senior Sergeant Ian Kerrisk warned people to think of the consequences of such an action.
"What people might think is a great lark from where they're standing, at the top of the hill, has the potential to end up with someone being killed.
"A tyre like that could cause considerable injury or death, if people, or even a vehicle, were in its path. It would pick up considerable speed once you let it go and you'd have no control over where it would go."
The wheel bounced over 3m-high boulders to land on Mr Robbie's section.
On Saturday morning, he had alerted police about a group of people "bowling" smaller tyres from the lookout up the hill.
It was possible the two incidents were linked and police wanted information about both.
