If so, what tire/wheel combination?
What problems (if any) with fitment?
Increased road noise or ride harshness?
Improved handling?

245/45 is the size to go when going to an 18" rim so lots of people use it.

I got Nexen N3000 rubber. Is a really popular tire around my area because it is well priced and lasts forever. I love mine and will never get a different tire as long as they continue to make them. Agressive tread design and great wear.

Their is no wheel fitment issues, same OD as stock. People run up to 275's without issues so your not going to get any with a 245 series.

I find their is improved response in handling, obviously you will notice a difference because its a wider tire but alot really depends on what tire you get. ie, directional, performance, all-season, what brand, things like that.

And I didn't notice a HUGE difference in ride, it does have a smaller sidewall so it will be a bit more bumpy but the difference in ride is not like night and day. the smaller rubber is just not as forgiving.

My road noise was actually decreased when I put on my new tires because my old ones had bit the dust but even these I don't hear them at all. Highway or city. My exhaust/motor is louder than these and I still have my resonator with summit muffs (its not very loud).

HTH.

Im running 274/40s and i have no rubbing at all. you should be fine

245/45-18 should be fine... It's the offset that could create havoc..... I put 245's on my car with a 35mm offset and had to work the rear fenders a bit because of minor rubbing over major dips and bumps. If I coulda gone with a 42mm offset I would have, and I wouldn't have had to work the rear fenders. The rim I wanted didn't give me that option.

i was running 255/45/18 and had no rubbing with 1 3/4 drop. so your fine

Well im running the 18x8 american racing casinos w/ michealin primacy tires, same sizing 245/45 i do believe and no rubbing at all and they ride better then the 16's did but I guess those had bad tires to begin with.

I am running 245/45 Falken 452's, I am very pleased with these. My rims have 40mm offset am lowered 1" and have no issues with rubbing

I'm running 245/45/18 and no problem at all.