Lesson Plan Industry Sector

Lesson Plan Originally Created By: Michael Drouin

Tire size By Michael Drouin

Part of Unit: Fundamentals of Steering, Suspension, Tires, Wheels

Lesson Plan Overview / Details

Fundamentals of tires

Instructional Time

2 Hours


California's 2008 CTE Standards


Students will:

  • Know where to find the tire size.
  • Understand the relationship between the numbers of the size and the actual dimension on the tire.
  • Learn a little history lesson on wheel/tire, like  how the drag race industry and now the drifting trend has affected the choice of aftermarket wheels people buy for their automobiles.

Activities in this Lesson

  • Introduction Hooks / Set

    I start the class with a big attention getter (race cars work well) I use a 1969 Lotus 61 Formula Ford. Students enter the class, most stand and look at the car, then start firing off questions. After I get them in seats, I start my lecture standing by the car. I talk a little about how amazing it is that with all the power and weight of an automobile, the only contact with the road is the small contact patch of the tire. I turn the steering wheel to expose the tire and say today we are going to learn about tire size. I have a collection of tires that I use to help students understand the history and tire size.

  • tire history Demo / Modeling

    I start with an old N-50-15 mounted on a Cragar rim. I talk about how this was the hot ticket when I was a teenager. I talk about how the racing industry has influenced the wheel / tire that people want on their car. I talk about how wheel/tire allows you to personalize your car.

  • Next I pull out a 155-80-13 and set it next to the N-50 15. Everybody see the difference? This is a 155-80-13, not very interesting. Does not say much about my car. Then I pull out the rota rim with a 315-45-18 mounted on it. This helps focus the students. I ask what is the big influence on wheel/tire today?  Someone will say Drifting. I agree most teenagers want a car that looks like a drifter. Now lets look at what makes this tire look this way. I pull out a large set of calipers. Use them to slip across the largest section of the tire. Set the calipers on the board, draw a line between the two points. This distance is 315mm. I show them the tire size stamped on the side of the tire. I say everybody got that. The first part of the tire size tells me how wide the tire is at its widest section. The next number is a little more difficult. Looking at the line on the board I say 45% of that line and adjust my calipers to about that size. Then I lay the caliper up against the side of the tire and show them that the calipers and the sidewall are the same size. The second number is the profile of the tire. How high the side wall is compared to the tread. Then I look at the 155-80-13 and ask should the second number on this one be larger or smaller than the 45%. Some one will say bigger and I tell them , you are right this is an 80%. Then point out the 80 on the tire.

  • Rim size Lecture

    I say the last number is the easy. I read it off the side wall 18. Who can tell me what the 18 means. If no one answers, I goad them a little…………come on what about a 22’s?  I want some 22’s for my car (or what ever the biggest rim is……………seems to get bigger every year) Some one will answer the rim size . I say yes, it is the size the rim that the tire fits on.

  • Then I have a couple of tires that I have the students come up one at a time and ask them to point out one of the three numbers . Then indicate what that dimension is on the tire.

  • review Closure

    By this time the class is close to being over, someone will want to hear the Race car start up. I say O.K. I’ll start it if you tell me what size tires are on it and what that means ZOOM ZOOM