Source: my entire life and, I suppose, http://canadiantire.ca
Thus, for example, Australia has a Labor party, not a Labour party (while neighbor New Zealand does have a Labour party), and typically sends people to jail instead of to gaol. Canada usually has tires instead of tyres, and Canadians realize things instead of realising them.
More information on Australian spelling: http://en.wikipedia.org/wiki/Australian_English#Spelling
Given you can't see points, hartror is correct, and here's a collection of tyre retailer names as evidence
Kmart Tyre & Auto Service
Welshpool Tyre Service
Berry's Tyres
Fremantle Tyrepower
Ian Diffen World of Tyres & Mufflers
West State Tyre Service
National Tyres
(you get the idea)
1) Are you Australian? (sub question, were you born Australian?)
2) What state/territory do you live in?
Because every state and territory I've lived in, it's been tyre. I've never seen tire used except by non-native speakers.