What size allen wrench is required to remove tires from a '99 Toyota Solara?

I'm sure you've already discovered the answer to your question a year and a half ago. But since I found your question by way of having the same problem, I thought I'd leave an answer for anyone else with our confusion.

The size Allen wrench you need to change a Solara tire is. Flathead. Yep. The screws aren't real. There's a notch that you stick a screwdriver into and pry off the cover, revealing the lug nuts. Who knew.