Drift Translator and Toe Angle Calculator

by Stan Pope


Various writers describe a test surface specification for measuring a pinewood derby car's "drift toward the rail" when preparing a car to guide using the center rail of a pinewood derby track. Various test surface lengths and drifts are used. Eight feet and four feet are common test surface lengths, although other lengths are often more conveniently available for most of us.

This page provides a computation tool to convert drift specs to test surfaces of different lengths. For instance, it can convert a 4 inch in 8 feet spec to the comparable drift on a 3 or a 5 foot surface. IF the car's wheelbase is specified, the tool also computes the toe angle needed to produce the specified drift. With the toe angle in hand, one can use this computation tool to guide in drilling the appropriate axle holes in a car body.




Since drift can be accomplished by toe on a front wheel or by toe on the rear wheels, or by a combination, communication would be enhanced if the drift measurement used a means of aligning to the reference which was consistent across all the ways of creating drift. That is, the drift measurement should be independent of how the drift was accomplished. When a rail guided car runs, the rear wheels travel a straight line. The car should then, be staged for drift measurement so that the rear wheels start straight down the track.

However, that straight line motion is difficult to discern. Small errors in aligning their initial path leads to large errors in the drift measure! Avoiding those large errors is more important than measurement consistency between the various ways of accomplishing drift. Therefore, I recommend that some long dimension of the car be aligned to the board's reference line and that the documentation include the method of alignment and the method for accomplishing toe.

Useful long dimensions for alignment include the side of the car that has the dominant front wheel, where the axles on that side of the car enter the car body, or the inner edges of the wheels on that side of the car body.


Drift Translator and Toe Angle Calculator

For the following computations, enter the lengths of the test surfaces (boards) less the length of the car. For an 8 foot board, enter 89 inches (or less) which is 8 feet (96 inches) less 7 inches.

Results are computed (if enough data is available) every time one of the inputs is changed. Inputs are changed when new values are keyed in and focus is changed to another input box (e.g. by pressing TAB or by clicking in another box.)


    Given test surface length (inches):

    Given test surface drift spec. (inches):

    Available test surface length (inches):

    Car's Wheelbase (inches):


    Computed test surface drift (inches):

    Toe angle (degrees):

Latest revisions:
2/15/2010 New!
2/26/2010 Add Staging caveat and Communication topic.

Known problems:
Copyright 2010 © by Stan Pope. All rights reserved.