[quote author=thereisnospoon link=topic=91139.msg1768213#msg1768213 date=1191914742]
Trust me - drive an SEL Fusion with the 17's and then drive the sport package car with the 18's on it. You'll find out that they are WORLDS different as far as handling goes, but I'd say that probably 10 percent...hell, less than that...maybe 2 percent....is due to the fact that you have 18's on there.
The biggest difference will be in your cornering, stop/start launch angle, the amount you rock back and forth, side to side, the amount you dip when you hit a pothole or a bump/hump in the road. All of this is mostly your suspension components much more than the tire.
I can't find the info on the 18" tire as far as sidewall height and width are concerned, but I wouldn't imagine that the ratio is any different from the SEL 17. That being said, most of what you feel is not the tire.
And, you're right - it's probably not just the springs, it's probably the shock and strut upgrade along with the rear sway bar...which has pretty much paid for the upgrade right there.
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I have driven both, that's why i'm asking what it takes. I'm no noob to the suspension game, i have a 1990 5.0 that has about every suspension trick in the book done to it. CC plates, saleen race springs, steeda billet rear lca's, braces, solid steering rack bushings, heim joint tie rod ends, yadda yadda yadda, and i don't want to play that game with this car. It cost me a hell of alot more to lower it correctly than just $200 springs. This is gonna be my daily driver. And it has to work in snow as well. The SEL has more sidewall period. and one of the biggest handling tricks you can do in the mustang world is change wheel size. That's why i asked if anyone had a car with 18's and how it compared to the sport pack. I'm guessing the springs to be a little bit, and i mean little, stiffer, same with shocks, and the sway bar is probably one they already have, just a mm or 2 larger. I wanna cheat a sel to handle like a sport pack if i ad 18's. I've already delt with the caster/camber and bumpsteer issues on my racecar and i don't want to do it again. If getting a sel to handle sharp like the sp car is easy and not too $$$ i'll do it. If not i'll either buy the sport pack or live with mushy cornering and a color i like.
Maybe i'll call ford tech and see what the diff in components is...