The original Pinewood Derby timer (the first Timestopper), built by Dr. Tullis and first used for a large (70 cubs) event in 1982, had a clock rate of 1 Megahertz, as did an earlier prototype in 1976, and was capable of resolving race times to within one microsecond (1/1,000,000th of a second).   It was carefully determined, however, to display race times to a resolution of only 1/1,000th of a second (0.001 second, or 1 millisecond).   Why is this 1 millisecond resolution important?   It has to do with "significant figures" as taught in high-school physics classes.

Given the design and scale of Pinewood Derby cars and tracks, 1/1,000th of a second is an optimum level of read-out resolution for a Pinewood Derby timer.   And timer precision needs to be as good as the read-out resolution.   One-millisecond precision and resolution can differentiate cars separated by as little as approximately 1/3 inch near the finish line.

The 1/100th second resolution of a common stopwatch is NOT sufficient, as it could (if combined with photosensor triggering) only differentiate cars that are separated by more than a few inches.   There would then be too many ties at the finish line.   This would not enable efficient determination of ultimate winners.

1/10,000 second precision and resolution is too much precision and resolution to be useful, since differentiation of cars separated by less than approximately 1/3 inch allows too many unwanted and uncontrolled variables to determine the outcome of a race.   For example, without expensive temperature compensation within the crystal time-base and electronics of a timer, the timer can thermally drift and shift race results by a good fraction of 1 millisecond.   Other factors influence race results by amounts less than 1 millisecond; these include drafts of air in the vicinity of the race, changes in vibration levels of the track, changes in stiction of the individual pegs of a start gate against the fronts of cars, differences in how the start-gate is operated from race to race, expansion and contraction of the track length caused by temperature and humidity changes, and many others.   In short, using timing precision and/or resolution of better than one millisecond will leave the differentiation between cars crossing the finish line, within about 1/3 inch of one-another, purely to chance rather than true performance.

It is therefore strongly recommended that Pinewood Derby timers be read to only the nearest 0.001 second in resolution.   This is to assure the fairest race results.   For the same reasons, even when averaging a car’s performance across all lanes of a track, only the nearest 0.001 second should be considered not only for the individual lane results, but for the final averaged result.