Tire Rack has a great explanation on how wheels are made. I bought gravity cast wheels, and I wouldn't have normally purchased this type of wheel. But I did, they failed. The TSW wheels I just purchased are rolled and forged... give the wheels more strength while keeping the weight down. So rolled, pressure casted, forged, or 3 piece wheels is what you want. Gravity cast wheels will be heavier, and may have weak points. So, those I would stay away from.