Performance all-season tires keep your car glued to the road through sudden summer downpours and chilly autumn commutes. They are not cheap to replace, especially when you need a full set of four, and running a sporty car means accepting that rubber wears down faster than you want it to. Waiting for the right moment to buy makes a big dent in the total bill.
You want to time this for when retail rebates are active, usually around major holiday weekends in spring or late autumn. Nail down the price of the tires and installation first before you talk about how you are going to pay for it. A financing window is just a tool to smooth out the cash flow, not a discount on the rubber.
That 0% window is a deadline, not free money. If you still have a balance left when the 18 months are up, deferred interest or standard rates will kick in on what you owe, so treat that monthly payment as a fixed bill until it is gone.