Bump Stops: Also known as bump rubbers, play a vital role in suspension design and are essentially an additional spring made of an elastomeric material. They help prevent the damper and/or spring from bottoming out. More about bump stops below...
As the suspension compresses two things will occur if there is not enough bump travel. The spring can "coil bind" or the damper can "bottom out", both leading to a situation where the effective spring rate becomes infinite (in other words a solid rod). When this occurs bad things can happen such as an abrupt loss of traction and/or possible damage to suspension components. This is why it is crucial to have the damper stroke position set correctly. However, even with the stroke position set correctly, large bumps can still cause the spring to coil bind or the damper to bottom out. Fortunately bump stops can help this situation. As the suspension nears bottoming out or coil bind, the addition of a bump stop creates a highly progressive spring rate, helping solve the problem of instantaneous infinite spring rate. This a great solution for smoothly controlling the wheel delivering a significant positive impact on ride comfort and cornering grip.
Bump stops can be used for more than just protection from coil bind or bottoming, they also can be used for tuning the suspension as well. We will go over this briefly here and in more detail in a future article. One thing we can do is set our stroke position where we are roughly 1 inch away from the bump stop. This will allow the suspension to soak up minor bumps using only the coil spring, allowing for a more comfortable ride quality. Then as the car goes into a corner and the suspension compresses, the upper spring perch will hit the bump stop reducing body roll from the increased spring rate. It is important to know that there are special bump stops for this where the first inch of travel of the bump stop can be made soft, and at a certain point the bump stop becomes much more stiff to combat coil bind or bottoming out. This a great solution for smoothly controlling the wheel delivering a significant positive impact on ride comfort and cornering grip.