Learn Car Stuff
Your entire car touches the road through four patches the size of postcards
Four Small Patches
A loaded car can weigh well over 3,000 pounds, yet it touches the road through four contact patches, each about the size of a postcard — roughly 20 to 30 square inches. Every force the car makes has to pass through that small area.
Pressure Sets Patch Size
Air pressure inside the tire does the real work of holding the car up, and the contact patch grows or shrinks until the pressure inside roughly balances the weight pressing down. Drop the pressure and the patch spreads out to compensate.
Braking Loads The Front
Hard braking shifts weight forward, pressing the front tires down harder and lifting load off the rear. The front contact patches grow while the rear ones shrink — which is exactly why front brakes do most of the stopping work.
Cornering Loads The Outside
Turn the wheel and weight rolls toward the outside of the corner, pressing the outside tires' patches wider while the inside patches go light. That's why the outside tires do most of the cornering grip — and why a sudden jerk of the wheel can overload them.
The One Number You Control
Weight transfer depends on how hard you brake and turn, but tire pressure decides how big each patch is to begin with. Check it monthly, cold, and set it to the number on the driver's door-jamb sticker.
