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Why calculate?
- To improve your score.
- To be more accurate.
- Anything else is just a guess.
- It's like having inside information – you know official leg time before you get there!
Odometer correction factor
Use the following formulas to adjust your speed to correct for any difference between your vehicle's odometer and Official Miles.
Odometer correction factor = Your odometer miles / Official Miles
Corrected speed = CAST X Odometer correction factor
Example: Your odometer miles = 9.1, Official Miles = 10.00, CAST 45
Odometer correction factor = 9.1 / 10 = 0.91
Corrected speed = 45 X 0.91 = 41 mph
If your odometer miles are less than Official Miles, you must drive slower. If your "odo" is greater than Official, you must drive faster to stay on time.
TSD timekeeping
Use the following formula to calculate precisely how long it should take to travel a specific distance at a specific average speed. If you calculate and log interval times and keep track of cumulative time,
then you you'll know exactly what time it should be (or should have been) when you pass a specific reference. Compare your actual arrival time with your calculated perfect time to find out how far ahead
or behind you were at that point. Slow down or speed up as needed, and start calculating your next reference.
Time = (60 X Distance) / Speed
Example: CAST 30 next 2 miles
Time = (60 X 2) / 30
Time = 4 minutes
Example: CAST 45 next 1.4 miles
Time = (60 X 1.4) / 45
Time = 1.87 minutes
Gain
To calculate how long it should take to complete a GAIN:
Interval time = ((60 X Distance) / Speed) – GAIN time
Example: CAST 30, then GAIN 1 minute next 2 miles
Interval time = ((60 x 2) / 30) – 1 = 3 minutes
To calculate what your average speed should be to complete this GAIN:
Average speed = 60 / (Interval time / Distance)
Example: 2 miles in 3 minutes
Average speed = 60 / (3 / 2) = 40 mph
60 rule
Here's a do-it-in-your-head tip. The speed at that increment of a mile takes 60 hundredths.
30 mph for 0.30 miles takes 60 hundredths (0.60 minutes)
35 mph for 0.35 miles takes 60 hundredths (0.60 minutes)
40 mph for 0.40 miles takes 60 hundredths (0.60 minutes)
45 mph for 0.45 miles takes 60 hundredths (0.60 minutes)
50 mph for 0.50 miles takes 60 hundredths (0.60 minutes)
55 mph for 0.55 miles takes 60 hundredths (0.60 minutes)
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