Example:

Tire size  = 225/55R17 ………………

= (W [mm])/ (100H/ W) R (D [in]) …….

From the above definition

W = 225 [mm]

100 H/W = 55

H = 55 W / 100 = 55 x 225 /100 = 123.75 mm

Tire diameter (d) = H + D + H = 2H + D

= ( 2 H  + D x 25.4) / 1000 [m]

= (2 x 123.75 + 17 x 25.4) / 1000 [m]

= 0.6793 [m]

Tire free radius (rw)F    = d/2 = 0.6793/2 = 0.3896 [m]

Tire free radius (rw)= X / 2

Measure the tire radius from the center of the wheel to the ground

Tire static radius (rw)S = y

a) Put a mark on the tire, put the car on neutral and push the car. Measure the distance car will travel (L) for (n) tire revolutions.

L = n x (2prw)

Tire rolling radius (rw)R = L / (n x 2p)                          [no tractive effort]

b)  Put a mark on the tire, put the car in first gear and drive the car slowly. Measure the distance the car will travel (L’) for (n) tire revolutions.

L’ = n x (2prw)

Tire rolling radius (rw)R = L’ / (n x 2p)                        [with tractive effort]

Report No. 1

A)

1. Write down the car make & model.

2. Write down the tire brand & name.

B)

1. Write down the tire's size of your car.

2. Explain each marking.

C)

1. Calculate the tire marked radius.

2.  Measure the

i- without tractive effort,

ii- with tractive effort.

D)

1.  Write down the tire maximum inflation pressure.

2. Write down the recommended tire inflation pressures (front, rear).

E)

1.  Find from the tire sidewall markings: the tire load index and write down the maximum load the tire can carry.

2.  Find from the tire sidewall markings: the tire speed markings and write down the maximum car speed the car can travel with this tire.