Wheel & Tires Adding Significant Levels of Grip One of the most popular upgrades, wheels can enhance the look and/or performance of your ride. Acceleration, handling, and braking can all be affected by the weight of the wheel. Just motoring around town, you may not notice differences in wheel weight. However, since this site is biased toward performance tuning, wheel weight can play a huge role factor. It is a matter of simple physics. First, lets talk about un-sprung weight. Un-sprung weight is defined by as weight that is not sprung…which means anything that does not ride on (supported by) the suspension (read wheels, tires, brakes, and axles). Since the wheels/tires rotate and are what transfer circular motion in to forward motion, their weight has the largest impact of un-sprung weight. It is easier to understand if you think about it in terms of a bicycle wheel/tire. If you have a small and a large bike turned upside down (so you can spin the front wheel with your hand), it takes more energy to get the larger/heavier wheel/tire moving than the small, light wheel. Also, once the wheel is spinning, the larger/heavier wheel has more momentum (mass x velocity) than the smaller and is more difficult to turn. Along those lines, it also takes more force to stop the heavier wheel. In a nutshell, heavier wheels can negatively impact acceleration, braking, and handling. Now there is the argument that slightly heavier wheels have no noticeable effect. Manufacturers try to strike a balance between light weight, durability, cost, and style (good looks). Scooby Poop (bottom line): Buy the lightest, strongest wheels that you like and can afford. Tires Stick to it Baby! The WRX is a great car in stock form. However, from the factory, the WRX is a capable handler...but not exceptional...on dry pavement. To turn your WRX into the serious sport car that is, the single most dramatic thing you can and should do is change the OEM Bridgestone RE92 mud and snow tires to a tire that actually grips the road. With the RE92, the WRX can be slid around with relative ease. However, once you put some decent, sticky tires the WRX transforms into a whole new beast. With the high performance tires, turn-in, steering feedback, and lateral grip is phenomenal! By switching to "ultra-performance" BF Goodrich KDW's (see tirerack's category descriptions…one step below "max-performance" and a few steps below "R" rated tires) lateral grip increased by .04-.08 g's depending on the corner. This translates into 5-10 mph faster through the corners (low to medium speed corners). Get the best/stickiest tires you could afford. If you want to stay with true "street" tires, Bridgestone S-03's, Michelin Pilot, Pirelli P-Zeros, BF Goodrich KD, and a few others will provide maximum performance. My personal preference is the Bridgestone S-03's...Great tread life (relatively speaking), quiet (relatively speaking), and pehaps the stickiest out there in standard street attire. The most economical choice is the Kumho Ecsta MX...great tire for the money. If you live in a dry climate you may be able to get away with "R" compound tires (Racing compound…most R compound tires do NOT have the ability to dispense very much rain/water and therefore hydroplane with relative ease). Also, R compound tires typically only last at most 10,000 miles. There are a few drawbacks that should be noted with high performance street tires. Though the WRX is not known for its quietness…the tire/road noise is much more audible. Also, stiffer sidewalls make the ride harsher…and the some tires will have a tendency to "tramline" (follow seams/cracks in the road). *thanks to Scoobytuner for the artical.