Tire Pressure Lab

Goal of the Lab

Determine the average tire pressure for a passenger vehicle.Measure the contact patch of the tire.Calculate the aspect ratio of the tire.Use data from lab to determine weight of the car.

Tire Pressure

Tire pressure measures the amount of air in your tire per unit volume.Units: lb/in2

Method: Place gauge on uncovered valve stem

and release air from tire into gauge. Read the gauge.

Tire Pressure Gauges

Contact PatchDef: The area of the tire that comes in contact with the pavement.

Contact Patch cont….

Method: Use a ruler to measure the area of the tire that is touching the ground.

Side Back

Side x Back = Area

Contact Patch cont….

Units: in2

Under or over inflated tires may result in an incorrect contact patch area!!

Aspect Ratio

Def: A comparison of the tire height to widthFormula:

100 (cm)Width

(cm)Height x

Aspect Ratio cont….

Low number= Low Profile TireGreater width than height

Weight of the Car

Weight is calculated from the contact patch and the tire pressure.

Formula: (Contact Patch in2 x 4 ) x (tire pressure

lb/in2)

Tire Serial Numbers

P 185 80 R 14

Type of tire

Widthin

mm

AspectRatio

RimSize in

inches

Tire Serial Numbers cont…

Data TableName and

type of vehicle

Contact Patch(in2)

Tire Pressure

(psi)

Weight (lb)

Height (cm)

Width(cm)

Rim Size (in)