MetroMPG wrote:
I think Sergey's right: sounds like a classic tire balance issue causing the vibration.
As for finding you have to use more gas to go fast, remember your speedometer is probably also off a bit. Larger circumference tire than stock means your speedo is now reading low. You're actually going faster than your speedo shows, so you would have to push harder than before to maintain the indicated speed.
You can use this tool to enter the stock vs. new tire size and figure out your speedometer error:
http://wildcatent.freeyellow.com/zookmods/calc.htmAlso, aggressive chunky rims, wider tires and taller ride height increases aerodynamic drag - so you need more gas to go fast.
They do look nice though!

is the speed also read wrong on the computer as well?
I am an advocate of having no rims larger than 15" on an aveo, the SRT rims are off a car that is pretty fast from the factory, Oscare could offer some insight though. Seems like all those problems are because of the new rims( it has been addressed), and the transmission may also have a problem with them, as if the car is telling the speed of the car to the tranny, while the car is going much faster