Sorry, I promised dyno testing news, but I'm going to discuss wheels and tires first. The dyno stuff will come later.
Although the stock wheels and tires on this car are pretty huge (18x8.5" wheels, 245/40R18 tires), the fenders are simply gargantuan, and there's a LOT of room in there for bigger rubber. So, not being the type to leave well enough alone, I got out the calculator. Lessee...there's probably an inch of extra clearance...That'd be around a 275mm tire width. A wheel that was one inch wider would be 9.5" wide...might as well go up a size in diameter, mostly for appearances...So that means a 19x9.5" wheel, 275/30R19 tire.
Scouring our various suppliers didn't result in many choices. Most mondo-huge wheels are in lower offsets than will work on the STI. And some that would fit are boat anchors weight-wise, or wouldn't clear the brakes.
One promising wheel was the Rays G-Games 99B. It's really light at 21 pounds. (Trust me, for this large of a wheel, that's light!) It comes in the right bolt pattern and size. But the highest offset is +40. Still, I couldn't pass up the look -- it's like the stock five-spoke, but bigger and more sculpted.
For tires, the choices were again limited. 275/30R19 just isn't something you're going to find at the local Tires 'R' Us. Cooper Tire came to the rescue with their Zeon 2XS. Some of you tire snobs might be asking, "Why not Pirelli or Michelin or some other fancy-pants tire?" Well, to be honest, I didn't want to spend $300+ per tire, and I find that our customers don't either. So I thought I'd try this brand. Plus, Cooper sponsors our friends at CSI Racing, and the team has had good results with the Cooper product.
Here's the result. It looks awesome! To me, the car looks more to scale with the wheels -- the larger wheels reduce the car's bulky appearance, especially at the back.
But there's some sad news, too -- the +40 offset is too far outward, so both front and rear tires are sticking out from the fenders just a bit. We haven't done full testing yet, but it looks like the fenders and tires are going to come into contact at full suspension travel. In theory we could have the pad (the center mounting surface of the wheel) machined down, but I don't think there's enough material on the wheel to allow that. So it's back to the drawing board, looking for an even higher offset.