As an example: A traditional balanced setup with a 600-pound RF spring, produces 1,700 pounds of load at 3 inches of shock travel. Alternatively, a balanced bumpstop setup might utilize a 300-pound RF spring, but engaging a bumpstop stack at 2 3/4 inches of shock travel achieves 1,700 pounds of wheel load at the same 3 inches of max shock travel. As you can see, both setups are now achieving the same wheel load at max travel keeping the balance very similar, but one very important difference exists.

The bumpstop setup with softer springs and bigger bar reaches its optimum load sooner, and maintains it for a much longer time frame through the corner. This fact has several major advantages.

The camber will be at its optimum settings for maximum grip much earlier in corner entry, through center, and remain longer through corner exit. The overall center of gravity of the car will also remain lower throughout the entire lap, also enhancing corner speed. Lastly, softer springs in the front will be in a more preloaded state, which can sometimes enhance rear weight transfer, further helping forward bite.

The simplicity of a good bumpstop system and ease of fine adjustments make bumpstops my number one choice for a suspension package wherever rules allow.

Drivers first impressions of a well-balanced bumpstop setup are usually that they have much more feel in the front of the car. The cars usually respond very quickly to small inputs in steering, and less overall steering input is usually required.

Bumpstops can have an advantage over coil-binding as well. With bumpstops you can fine tune the weight distribution and crossweight settings much more easily without changing any critical dynamic chassis heights or stop heights. Bumpstops also can provide much more compliance than the coil-bind setup making it a better choice when rough track surfaces are a concern.

In closing, a well balanced bumpstop setup using soft springs is much closer in relative wheel rate to our older traditional setups than many ever realized. Understanding and applying these traditional principles in a new way could be all that's needed to help keep you ahead of your competition!

A New Line of Bumpstop Products
To take this technology further, Mercer Race Car Engineering has partnered with Steele Rubber Products to develop a brand-new line of bumpstop products. Phantom Bump Stops offers a variety of different bumpstops and accessories, as well as spring rubbers. It also offers a brand-new, Preload Adjustable Bumpstop System that gives racers more adjustability in their packages than ever before.

This new system contains a preload adjustable cup or canister that the bumpstops are contained in (see the pictures on the following page). That provides the ability to preload the bumpstop stack to change the effective rate of the contained bumpstops. To create more load and stop travel sooner, you now only need to increase preload in small increments instead of adding packers as previous systems would require.

This allows fine-tuning the dynamic travel or stop height without changing the timing of engagement or air gap. It also provides the ability to run much softer bumpstops than previously possible by allowing you to set the desired travel distance into a bumpstop stack by changing the preload.

Mercer Race Cars
Steele Rubber Products