# Auto Tire Pressure

Activity Overview: Students will use a tire pressure gauge to determine if the tires are properly inflated. Students will learn how under inflated tires effect gas mileage for a vehicle.

Time: 1 hour

Materials: tire pressure gauge, clipboards, ribbons, pens, copies of Tire Pressure Worksheet

Vocabulary: under-inflated, tire pressure gauge, psi, mpg

## Background Information:

America is driving around on under-inflated tires, according to a recent survey. Under-inflated tires lower gas mileage, wasting millions of dollars each year. Under-inflated tires are also a major safety hazard. Thousands of accidents each year may be caused by poor handling due to under inflated tires.

### Interesting Facts:

• One out of three light trucks and one out of four cars now on the road has a tire that’s significantly under-inflated according to a recent NHSTA survey.
• You can improve your gas mileage by 3.3 percent by keeping your tires inflated to the proper pressure. Under-inflated tires can lower gas mileage by 0.4 percent for every 1 psi drop in pressure of all four tires. Properly inflated tires are safer and last longer.
• Six percent of light trucks (sport utility vehicles, vans and pickup trucks) are driven with all four of their tires under-inflated by 8 or more psi, compared with 3 percent of passenger cars. Twenty percent of light trucks have two or more tires under -inflated by 8 or more psi, compared with 13 percent of passenger cars.
• NHTSA estimates that 49 to 79 deaths and 6,585 to 10,635 injuries could be prevented annually if all vehicles were equipped with tire pressure monitoring systems. In addition, vehicle owners would benefit from better vehicle handling, increased tire life and better fuel economy.

## Setting the stage:

Ask your students if they have ever used a tire gauge, seen their parents add air to a tire, or if they have ever had a flat tire. Discuss gas mileage and factors that may affect it, and reasons why you want better gas mileage (less gas used, less energy usage, less money)

### Activity 1: So, when was the last time you checked your tire pressure?

Take the students out to the parking lot and show them how to check the tire pressure on a car. You may want to ask your high school auto mechanics class to bring a car over and show the students. Have the students fill out the tire pressure chart.

Send a tire pressure gauge (about \$2 at an auto parts store) home with your students if their parents do not have one. Include the Tire Pressure Worksheet. Have the student research the proper tire pressure for their particular car and record it on the pressure chart. Then they should record the actual tire pressure for each of the tires on the car they researched. In class, total the number of under-inflated tires.

### Activity 2: Calculate Efficiency Impact

Students will calculate the impact on efficiency for a specific example vehicle. Either use the "demo" car from the previous activity or ask students to use the measurements that they recorded from their vehicle at home. To do this, first subtract the actual tire pressure from the recommended pressure provided by the manufacturer. This is the difference in psi from normal pressure. Then multiple the difference in pressure by 0.4. The product is the impact in percent efficiency.

For example, if the manufacturer of an American mid-range light SUV recommends 35 psi per tire. The actual tire pressure is 33 psi in each tire. That is a difference of 8 psi (2 psi across 4 tires). The difference in psi times the efficiency impact of 0.4 is 3.2%. Therefore, this vehicle is suffering a 3.2% impact on efficiency.

### Activity 3: Teacher Tire Check

Have the class survey the school parking lot. Students give ribbons and information to teachers the day before the tire check. If teachers want their tire pressures checked they put the ribbon on their dash or rearview mirrors. The class then checks all the marked cars in the lot and leaves a note card under the windshield wiper with the pressures for each tire recorded.

### Extension:

For upper grades or as a club project you may provide an option to the tire check, an “Air Station” you set up after school to get under-inflated tires pumped up. (This will require some air compressors, hose, etc.) Or this could be coordinated with a nearby service station that would permit students to help people get their tires inflated.

Handing out driving tips, recommended maintenance tips and mile per gallon calculators at the same time is a good idea.

TEKS

Science: 6.1 (A), 6.2 (A, B, C, D, E), 6.4 (A), 7.1 (A), 7.2 (A, B, C, D, E), 7.4 (A), 8.1 (A), 8.2 (A, B, C, D, E), 8.4 (A)

Math: 6.3 (D, E), 7.3 (A, B)

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