will 235/45ZR/18 tires be ok on my element ?
thanks?

Yes they would fit, but no in my opinion. Your dropping in diameter, so in turn your engine will be at higher rpm's at any speed. Your mpg's will go down, its automatic, it puts strain on your trans, and will look silly.
Go with a 235/50 or 235/55, the 55 looks good imo.
Later
Steve

I use 235/50-18 Falken Zeix 912's. Didn't effect the speedo at all, and have great traction.