Some after-market wheels will puddle rainwater on the inner hoop, and that will feel like your wheels are out of balance. My Forgelines did it (fronts only) on a recent rainy trip. When I got home I went into the tire dealer and had them rebalanced, and they said they were only a "little" out of balance. After the rebalance they were perfect again, but they were dry. I notice the puddle of water accumulate on each wheel after each wash, and driving does not expel the water. At speed the puddle will stay in one location and make the wheel out of balance by a couple of ounces. The only way I can get it out is to stick a towel through the mesh openings and soak it out.
I never noticed this puddling problem with my stock 20" wheels.
Mods: Ridetech coilovers, prothane bushings, braided brake lines, Pfadt ZL1 style sways, Hawk ceramic pads, Spohn trailing arms, Kooks 1 7/8 LT's, HF cats, Magnaflow 3" cat-back, MBRP rec tips, Cold Air Inductions black CAI, MGW short-throw shifter w/retro shift ball, Showstopper Engine Bling, Forgeline MD3P's 9.5 & 11", Conti DWS 275's & 315's. JDP harness and DRL's. Seibon carbon fiber GFX, Anvil carbon fiber rear spoiler. Oracle ghosted LED side marker lights.
Proud previous owner of: 1968 327 Camaro, 1972 Camaro SS 350, 1978 Z28, 1979 Z28. 2010 SS is My 5th Camaro