K&C Testing Tips

Suspension Droop Limiting

Part of the test procedure in K&C testing at Morse Measurements involves lifting the car off the pads, zeroing the load cells, and resetting pad positions. This is done before the start of each test. For stock cars, this means you should have shocks on the front of the car and shocks and / or droop limiting chains on the rear axle. For all cars, you should be sure that when the car is picked up, the springs don’t have the opportunity to fall out or misalign. Springs that require baby sitting on each vehicle lift slow down your K&C test. Further springs that are not seated properly lead to incorrect measurements, general dismay, and sad pandas.

So what happens when you want to change springs on the K&C rig?

For stock cars, the procedure is to disconnect shocks and chains (as well as any vulnerable linear pots, which make poor droop limiting devices), then lift the vehicle very high such that springs can (usually) be removed. Once springs are removed and the new springs are in place, the car is brought back down to static ride height. At this point, shocks and any droop limiting chains and linear pots are reinstalled.

For sports cars, open wheel, and prototype cars, we can touch the tires down on the pads such that the coil-over units may be removed. Some sports cars may require the wheels to be removed to change springs. This is more time consuming, but also may be accomplished on the K&C rig.

After springs are installed and droop limiting is in place, we go to a “micro bounce” test to set / confirm the vertical load. This is roughly equivalent to setting corner weights on the ground, except that each corner of the car is independent of the others, making it easier to hit your desired targets. The large, live weight display projected on the wall at Morse Measurements makes this easy! By the way, the micro bounce test cycles the car up and down over a very small displacement such that we overcome suspension friction and can measure vertical load in the middle of the friction loop. Otherwise we will always be measuring either one side or the other of what can be a very significant friction loop, leading to inaccuracies in vertical load.

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