He was in the wrong offering the next in line the tires at an inflated price. Your bid was legal and binding. If, you read the mumbo jumbo in fine print saying to contact within 3 days point that out to him. If he tries to back out of your winning bid contact eBay immediatly. He can be knocked off of eBay with that kind of ethics. Did you notice how many sales he's had in the past? What kind of feedback he has?
I would personally contact eBay. They can help you with the problem.

Good luck,
Deby