Every return to a restrictor plate track brings suggestions about how we might eliminate the restrictor plate. Restrictor plates serve the very necessary function of limiting car speeds at Daytona and Talladega so that the cars stay on the ground. The negative is that they remove throttle response. One suggestion from some readers that I hadn’t heard of before suggested that NASCAR could just change the rear-end gearing parameters to shift the power curve and reduce horsepower that way. Will that work?
NASCAR engines like to run at about 8000-9500 rpm (revolutions per minute); however, the tires on the car rotate around 2400 rpm at 200 mph. The gearing in the transmission and the rear end gear reduce the rotational engine speed, with different gears providing different reductions. When you talk about the size of a gear, you’re actually talking about the relative sizes of a pair of gears. The gear on the left in the diagram has 20 teeth, while the gear on the right has 10 teeth, so this gear would be a 2:1, meaning that the smaller gear rotates twice every time the larger gear rotates once.
The defining characteristic of the Kansas race was the surprising number of engine problems. Many of those problems can be attributed to the change in rear gear from a 3.89 to a 4.00. At 190 mph at a track like Kansas, your wheels make 2270 revolutions per minute (rpm). If you watch the telemetry on the television broadcast, you know that the engine is rotating around 9500-9900 rpm. Since the engine is attached to the wheels, there has to be something to change the rotation rate between the engine and the gears.
The big news for Pocono is that drivers can shift…again. Which brings up the obvious dual questions of: Why would you want to? and Why didn’t you before?