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This will give you a pretty good ball park of the ratio, which can be compared with known ratios (4.11, 3.78, 3.54) to see which one comes closest. For example, put a mark on the brake drum, straight up or down is convenient, then rotate the pinion or engine in high gear, 2 revolutions.
If the brake drum mark indicates slightly less than one turn for the two pinion rotations, it indicates lower, higher number ratios such as 4.11 or 4.54.
DETAILS:
- Make a chalk mark on the bottom or top of the tire or brake drum
- Rotate the engine or pinion shaft clockwise exactly 2 revolutions.
- Measure the rotation on the tire or brake drum. It will be plus or minus one turn.
- Take this tire or drum rotation value, divide it into 1 (in other words, find its reciprocal),
- Then multiply it by 4.
EXAMPLE:
4(1/X) = 3.54
X = 1.12 (Drum or tire rotation value)
CLOCK BIG HAND INDICATION:
1.12 x 12 = 13.44 or about 10:30
A) Between 1 and 2 o'clock, ratio is 4.44
B) Between 12 and 1 o'clock, ratio is 4.11
C) Between 11 and 12 o'clock, ratio is 3.78
D) Between 10 and 11 o'clock, ratio is 3.54
GRAPHIC
