Originally Posted by MaysEffect

Alright then...With that bit of info out of the way. I recommend you holding off on duct tape splitters unless you absolutely need it for cosmetic purposes and get a good set of summer tires and brake pads.

YES, a well designed splitter (not a difficult task) will grant you a extra bit of handling feedback. But its a waste if you don't have a set of tires that will gain you actual lateral grip.

The basic gains from any functional splitter design is to reduce turbulent drag on the front tires. IF you've ever driven a really high riding truck or a car missing the front bumper altogether, you'll realize just how bad this drag is on the tires. That small percentage of air that still makes its way under the front bumper and on to the tires is still a large amount but not enough to warrant wasting money on some stick on chin guard.

Next would be to make additional downforce and further decrease pressure under the car. This is where a diffusers comes into play. These pieces of kit aren't cheap, and if they are, they probably aren't worth doodoo. Going back to point one. IF you don't have the proper tires to deal with this extra bit of force, then again it's a waste of money.

Ultimately -
You'll probably net the same amount of drag reduction by simply lowering your car a inch over some off the shelf splitter. So you can spend 200+ dollars on a splitter, or the same amount on a spring kit that may or may not be more functional overall (i say may because not all spring kits are made equal).

But before all else.

Tires is priority. Staying with the same diameter tires is also not a issue. You have a very broad clearance window of 25-27" overall rolling diameter depending on the width.

If you are using stock wheels. I'm assuming, front or rear, you are still smaller than a 18x10 wheel. So you can fit any tire up to a 285/35 comfortably (if you have at least a 9.5" wheel). IF your car has the smallest wheels, i'd move away from the large tires anyways and change to a 225/45 - 255/40 at the very least. This may look weird given the massive wheel arches, but the tire selections and handling characteristics would is much improved.

Lastly, Michelin PSS tires are a waste of money, they are old stock and still cost too much compared to the competition. You have several other options that will perform better. Why do you need run-flats? That's an additional cost that ultimately is not necessary unless you plan on going off roading. Tirerack offers road hazard protection for probably the same amount of money you'd spend on a set of run-flats compared to a non-RF tire.