If you have a computer or correctable odometer, you should already know how to use it.

If you're running a trip odometer, here's how to check it.

Stop your front wheels at the START sign and ZERO YOUR ODO.

Try to follow the exact route indicated to the end of the ODO CHECK. (Any off course mileage will render the check meaningless.) Avoid unnecessary lane changes as they accumulate unwanted mileage.

At the sign (listed in instructions) indicating the END of the ODO CHECK, pull over in the parking lane and STOP with your front wheels even with the sign. DO NOT STOP IN THE TRAFFIC LANE.

Look at your mileage and read it out. Navigators -- write it down!! If you have an odo with little number wheels (as opposed to a digital display), try to extrapolate hundredths of a mile by guessing relative location between tenths. Example: Your "tenths" mileage wheel is exactly halfway between "2" and "3" -- the guess would be ".25". Use your best guess for calculations. Pull away from the sign as soon as possible.

Now, having measured the mileage, compare your odo readings to the rallyemaster's. First, is yours lower or higher?

Here is one method for obtaining a "conversion factor":

Divide your mileage by the rallyemaster's and express the result as a percentage. For example, say your measured mileage was 22.1. The odo check on THE HOME RUN is 22.364 miles. 22.1/22.364 = .988 22.1 miles = 98.8% of the rallyemaster's indicated mileage. So, you need to add 1.2% to your odo reading (the difference between your percentage and 100%). 10 miles on your odo would equal about 10.12 miles on the map (rallymaster miles).

Second example: Your odo reads 25.6 miles. 25.6/22.364 = 1.145, or 114.5%. Subtract 100% and you get 14.5% over the rallyemaster mileage. Thus, when your odo shows 10 miles, subtract 14.5% and you get an adjusted mileage of 8.55 miles. Alternately, if you knew you needed to travel 10 miles, you would need to wait until your odo showed 11.45 miles to reach that distance.

You may also use the dividend obtained above as a "factor" instead of a percentage. Simply multiply the map (rallyemaster) mileage by the "factor" to get the mileage that will be shown on your odo. From example 1, above, 30 miles on map would convert as follows: 30 X .988 = 29.64. Your odo would show 29.64 at a map reading of 30 miles. From example 2, above, 30 miles would convert as follows: 30 X 1.145 = 34.35. Your odo would show 34.35 miles.

 Similarly, if you want to convert your odo reading to map mileage, you divide by the "factor". From example 1, above, if your odo showed 30 miles, convert as follows: 30/.988 = 30.36 map miles. From example 2, above: 30/1.145 = 26.20 map miles.