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Tire-shake Correction
By Jeff Burk
12/22/05
 ight after the whereabouts of Judge Crater and what happened to Jimmy Hoffa, one of the great mysteries is what drag racers refer to as "tire shake." There are many theories as to what causes the rear tires of a drag car under acceleration go "square" and in some case either shake a car to pieces or knock the driver unconscious or both.
I can remember years ago walking into Buddy Ingersoll’s trailer when I was traveling with him and his factory-backed turbocharged Buick Pro Stock/Pro Mod and finding GM engineer Bernard Santavy sitting on one of the wheel wells with a lap top computer in hand, totally engrossed in something and oblivious to anything going on around him. After a while
I nudged Buddy and asked, “What is Bernard doing?” Buddy answered, “He’s trying to figure out what causes tire shake.”
That was some 20 years ago and to my knowledge no one can yet state categorically what causes tire shake. But now, apparently one company has developed an electronic device that can detect tire shake and perhaps stop it: Davis Technologies, which in the past has been famous for it traction control devices.
Whether this is something that Ray Alley and Don Taylor at NHRA would be happy to see being tested and marketed is questionable but, according to the company’s Internet catalog (www.dragtraction.com), they have already had NHRA pro cars testing the unit.
Here is the info verbatim that DRO got from the company rep Toby Graham who is a regular visitor in many of NHRA professional pits.
"The Shake-Meter™ is designed to give racers a means to identify tire-shake in real time and correct it. After studying and comparing data from a clean run and a run where the car encountered tire shake, it became evident that when a car goes into tire shake the rear shocks consistently look the same. The shock trace will turn into a sine wave with a net negative slope. The beginning of this sine wave is only evident if the shock signal is
sampled at a very high rate. With that in mind, I developed a device that will monitor the shock signal and when this sine wave is detected a signal is outputted. The unit requires four connections: 12v (16v is fine), Ground, RR Shock and Output.
"The RR Shock signal is shared with the data acquisition system. The Output can be connected to a retard stage of the ignition system. Some racers think that switching the shocks to a stiff setting might be the ticket. For the sake of tuning the unit, the Output can also be routed to a channel in the data acq system. This will allow the racer to monitor when the unit is making a correction.
"The unit has a turn-pot on the front of the housing that allows the racer to set a threshold for activation. The higher the setting, the higher degree of tire shake is required to trigger the Output. The unit will detect tire shake in 24 thousandths of a second."
Whether NHRA or IHRA officially endorse the use of this product may be a moot point as it is available to racers and evidently is or has been used. Once again, the sanctioning bodies may be faced with the prospect of trying to shut the gate after the horses are already out. 
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