About PMI
Engineered Carbon Fiber Parts
Understanding Polar Moment of Inertia (PMI) and Its Impact on Handling
Polar Moment of Inertia (PMI) refers to an object's resistance to rotational acceleration. In the case of the NSX, its mid-engine design results in a low PMI, meaning the majority of its mass is concentrated within the wheelbase. This enhances cornering and turn-in response, making the car feel more agile.
By contrast, a front-engine, rear-wheel-drive vehicle—such as a Camaro—has a higher PMI, with more mass distributed toward the front and rear extremities. This results in a slower response to directional changes but often provides a smoother ride.
How PMI Affects Handling and Ride Quality
A lower PMI leads to sharper, more responsive handling, but it can also make the ride feel harsher. Adjusting your damper settings may be necessary to strike the right balance between comfort and handling performance.
A Simple Experiment to Visualize PMI
To get a hands-on understanding of PMI, try this simple test:
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Hold a full carton of eggs lengthwise (representing a car’s mass distribution) and rotate it back and forth—notice the resistance.
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Remove two eggs from one end (simulating weight reduction at the front or rear, like removing heavy OEM bumpers) and rotate it again—observe the change.
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Now, remove two more eggs from the opposite end and rotate once more. The reduced mass at the extremities makes the carton easier to rotate, demonstrating the effect of reducing PMI on handling dynamics.
Optimizing Your NSX with Weight Reduction
To further enhance balance and responsiveness, we offer a front prepreg bumper designed to optimize weight distribution.
⚠️ Important: After installing lightweight bumpers, handling will become noticeably quicker due to the removal of approximately 40 lbs from the far ends of the car. This is a significant change, so please exercise caution when adapting to the new driving characteristics.
Lastly, don't confuse Polar Moment of Inertia (PMI) with Moment of Inertia (MOI)—these are distinct concepts. We'll cover MOI in greater detail when we introduce our upcoming Brake Kit (BK).