My 225/45R17 tyres are already scraping my rear bumper under heavy passenger load... happened last week, had to put 4 mat sallehs into my car when going out for lunch... But with the correct offset 8.5" rims, you can actually fit 245/40R17 tyres at the rear, that's the normal size at the rear when running staggered rims.
Note that you will have some problems with the accuracy of the speedometer if you wanna put 235/45R17 at the rear... it may even start to under-read, meaning that you are actually going faster than what is shown on the meter. With 225/45R17, my speedo still over reads by a few km/h, no big deal, it's designed that way I guess for all the car brands that I know of... to boost ego and to prevent manufacturers from getting sued by car owners over speeding tickets...