I am planning to redo my garage floor, and we like to use it as a gym and, on occasion, to bring the cars in. would the rubber floor stand the weight of the cars, or we need a 1" floor?

A car can easily drive over our 1/2" Rubber Gym Tiles. These rubber tiles are our toughest tiles and will not indent under the weight of the car. These tiles are vulcanized like the tires on your car. The only problem that may arise from parking a car over our rubber flooring is that if any oil gets on the tile from the car, over time, the tiles may start to break down. For most cars, oil leakage if pretty rare, so this is not an issue for most installations.