RC (radio-controlled) car suspension refers to the system of parts that connect the car's body to its wheels and allow for the absorption of shocks and vibrations while driving on rough terrain. There are two main types of suspension systems used in RC cars: solid axle and independent suspension.

A solid axle suspension, also known as a "live axle" suspension, is the simplest and most common type used in RC cars. It consists of a single solid piece of metal connecting the two wheels on the same side of the car. Because the wheels are connected, they must move in the same direction and at the same speed, making this type of suspension less efficient in handling rough terrain and uneven surfaces.

On the other hand, independent suspension is a more advanced system in which each wheel is connected to the car's body separately. This allows for greater flexibility and control, as the wheels can move independently of each other. Independent suspension is typically more expensive and complex than solid axle suspension, but it is more efficient in handling rough terrain and uneven surfaces.

In addition to these two main types of suspension, RC cars can also have a variety of other features such as oil-filled shocks, adjustable spring rates, and sway bars to fine-tune the suspension for optimal performance on different types of terrain.

In summary, the main difference between solid axle suspension and independent suspension in RC cars is the way in which the wheels are connected to the body. Solid axle suspension is simpler and less expensive, but less efficient in handling rough terrain, while independent suspension is more advanced and efficient, but more expensive and complex