The biggest dirt bike size is a category that can be confusing for riders and parents. At one end of the spectrum, you have mini bikes that are typically ridden by children. These bikes are usually smaller than adult dirt bikes and often feature smaller engines. At the other end of the spectrum, you have full-size dirt bikes. These machines can be very large and feature powerful engines that make them well-suited for experienced riders. They can also be expensive, so it's important to find one that's right for your needs.