kopfjager

I have 255/45/18 and 285/40/18 both very close to overall stock height.

Philostang

Whose Apples, whose Oranges!? Whose on First? I wanna be an Orange. Man has it been a long day at work! [&o]

Good point Scooter. But the stock 18" upgrade wheels are 235/50s.

Anywho, there's a really slick tire/wheel calculator available from Rick Tolan:
http://gs.tolan-hoechst.com/tirecalc.htm

Uh-oh, research tools, now we're getting dangerous. I'm also fond of stuff that has proven it works--ex: Roush runs 18x10" rims on all four corners with 275/40s on their new StageIIs (which are lowered). Rumor has it that they use +45mm offset (that rumor has been rather unscientifically confirmed by me, but at the moment I think it is correct). Bottom line is that I don't think you should worry too much traffic, what you're interested in can be done. Pip-pip, chin-up, cheerio good man!

Also, I've matched Tolan's calculator results to other data available, so I'm inclined to trust the conversions it produces.
Best,
-j

GGIII

Okay, so I'll want a 295 series tire then. I want to hit up as much as possible, rubber wise, without affecting the appearance of my car.

So, what size tire do you reccomend? I've got a 1"f/1.5"r drop (18x9f/18x10r wheels.)

I want to keep the OD of my tires (relatively) the same as the O/D tires.

MR.Mustang

I have a lowered GT with 265 35 r18's and the ride is very firm. 35 series tires make for a rough ride. Also, your risk of damaging the rim increases when driving over pot-holes and such. There is still a lot of room before rubbing. You may also want to consider the offset of the rims. The lower the number offset the farther the rim sticks out. I have 45MM offset same as stock. My advise is to not go lower then a 40 series tire.

Also, a neat trick is to get all the same size tires all around and get a high quality spacer (1" or 1.5") to make the back look like they are wider. This will be better on the wallet and make tire rotation easier. I think I will go this route with my next set of tires.

Philostang

+1 on the "don't go lower than +40mm offset"

Correction: the OEM 18x8.5" bullit wheels have +50mm offset. 17x8"s have +45mm offset.

On a Side Note: Mr.Mustang, your avatar scares the bejesus! out of me every time I see it.

Best,
-j