wouldnt you have less rubber on the pavement why would you want that? i think 235/45 means that from the lip to lip its 235 centimeters and 45% of that is sidewall 235/55 would mean that 55% would be sidewall. unless you are changeing the rim size no point. what you want to do is go up to a 245 tire.
never mind i read it backwards, anyway you will have a shorter tire that way so more rubber on pavement but more of a gap between the top of the tire and the wheel well. I still say go up to a 245.
235 is the width of the tread in mm's, 45 is the sidewall height expressed as a percentage of the width (ie: 45% of 235 = 105.75mm sidewall height). The 235/45's will only differ from your 235/55's in the overall height of the tire, 45's will be shorter. A 10% difference comes out to ~23.5 mm difference in sidewall height, or twice that in overall height of the tire. As long as the tires are designed to fit your rim diameter, 17, 18, or 20", there should be problem, though going to a different height tire will throw off your speedometer some.
you would be stupid to go with a 235/45/17. Your sidewall would be 10% shorter! You'd be rolling around looking like a ******. If you want less sidewall, you need a bigger rim. If you want a better looking tire, go with a 255/50 or even a 275/50(or45)/17. If you go with the size of tire you want, your speedo will be way off.
Okay guys thanks for everything! So you guys suggest I go with the 255/50?? Ill take your advice. Just to make sure im still going to use my stock rims. So that shouldnt be a problem with fitting right?