Wheel deflection is the calculated difference in height between an unloaded tire section height and the under-load tire section height, typically measured from the tread face/shoulder to the wheel flange. It represents the amount the tire compresses under load. In simpler terms, it's the difference in how tall the tire appears when it's not supporting any weight versus when it is. This difference can be expressed as an amount (e.g., inches or millimeters) or as a percentage.
Here's a breakdown:
- Unloaded Tire Height: The distance from the road surface (or ground) to the top of the tire when the vehicle is not resting on it.
- Under-Load Tire Height: The distance from the road surface to the top of the tire when the vehicle's weight is applied.
- Deflection: Unloaded Tire Height - Under-Load Tire Height
Why is wheel deflection important?
Understanding wheel deflection is important for several reasons:
- Ride Comfort: Tire deflection directly impacts the vehicle's ride quality. Greater deflection generally translates to a softer, more comfortable ride, as the tire absorbs more of the road's imperfections.
- Handling: Deflection characteristics influence a vehicle's handling. Too much deflection can lead to a feeling of "squishiness" or reduced responsiveness, while too little deflection can result in a harsh ride and reduced grip.
- Load Capacity: Tire deflection is related to the load capacity of the tire. Manufacturers specify a maximum load for a given tire at a certain inflation pressure, based in part on acceptable deflection limits.
- Tire Wear: Excessive deflection can contribute to premature tire wear.
- Vehicle Dynamics: Engineers consider tire deflection when designing suspension systems to optimize vehicle dynamics.
Calculating Deflection Percentage:
Deflection Percentage = ((Unloaded Tire Height - Under-Load Tire Height) / Unloaded Tire Height) * 100
This percentage gives a relative measure of how much the tire is compressing under load.
