McGrew's MiscellaneaDerby

Derby Rules
for a Shape N Race Derby, Pinewood Derby, etc.

Shape N Race Derby, Pinewood Derby, Kub Kar Rally—whatever you call it, a derby is a lot of fun, and it's a great opportunity for learning and for making memories.

Here are some of my thoughts on writing derby rules. You can skip ahead to our church's rules, but remember that these are just our local rules. If you need a copy of your derby's rules (or if you need a clarification of those rules), then contact those in charge of your derby.

What to Consider

The nice thing about standards is that you have so many to choose from. – Andrew Tanenbaum

The "rules in the box" vary from one kit supplier to the next, and are often just assembly instructions, rather than actual rules. Your organization may or may not publish rules in their derby materials, and you may or may not want to expand, clarify, or revise these rules. For better or for worse, part of organizing a derby is establishing its rules. Here are some points to consider as you draft your derby's rules.


A weight limit is essential because heavier cars have an advantage over lighter cars. The traditional weight limit of 5 ounces works well, and most derbies use it.

Furthermore, cars must fit the tracks on which they will race. They must comfortably straddle the center lane guides or comfortably fit between the side lane rails (depending on the design of the track). They must fit the starting and finish gates. Also, they must not interfere with each other when racing in adjacent lanes.

Regional Derby Rules

If your organization sponsors a regional derby, then your local rules should be compatible with the regional rules. A car that races successfully in your local derby should be able to advance to the regional derby without modification.

That does not mean that the rules must be identical, however. For example, it is perfectly acceptable to specify a lower maximum height if your electronic finish gate is lower than the one used for the regional derby. You could even specify a higher maximum height, as long as you make it perfectly clear in advance that cars above the regional maximum height will not be able to compete in the regional derby.

Avoid Ambiguity

The rules should be clear and unambiguous. Clear, unambiguous rules help avoid surprises and arguments at the inspection table.

If an ambiguous situation does arise during registration or during the derby itself, then there should be a single person (e.g., the derby chairman) whose decision is final. Do not let the situation deteriorate into a long argument over whether a particular design is legal. However, it will usually be better to err on the side of leniency. Regardless, make sure to resolve the ambiguity before the next derby (e.g., during a leaders' debriefing meeting a week or two after the race).

Just Building the Car

A derby car is a simple project. It should be possible to "just build the car" without unintentionally violating a rule and being disqualified.

I think it is best to avoid rules that make it more difficult for inexperienced child–adult teams to build a legal car. For example, if one simply inserts the axles into the pre-cut slots, then the car will probably rest on only three wheels when placed on a hard, flat surface. It is actually fairly difficult to get a derby car to rest evenly on all four wheels. Therefore, I recommend against "four on the floor" rules that require cars to rest evenly on all four wheels.

As another example, our starting gate can accomodate any shape car body that can be cut from the original block of wood. The starting pins are long enough to reach to the top of an uncut block with wheels and axles mounted, and the position of the starting pins in the lane matches the sensors on our finish gate. Those who "just build the car" do not need to worry about our "fit the track" rules.

Preserve the Nature of the Project

A derby is a race between gravity-powered cars on an inclined track. Most rules prohibit designs that would draw energy from any other source.

But beyond that, what designs and construction techniques are acceptable? Most controversial rules will fall into this category, because people disagree about what the nature of the project is, and about what construction techniques are appropriate (or inappropriate) for the project. Where do you draw the line between building a derby car well, and doing something essentially different (even though it might produce something that can roll down a derby track)?

For our derbies, the car is fundamentally a child–parent (or child–adult) project. The point of a derby is not the race itself. Rather, the point of a derby is the interaction between children and adults that takes place during the construction process (and to a lesser degree, during the race). Therefore, we do not try to restrict parental involvement. To redirect over-eager parents who might take over the project, we conduct an All Comers race. Parents can build and race their own cars, and can use their own cars to demonstrate construction techniques to their children.

Most derbies require everyone to use the wheels and axles supplied in their official kits. Using other wheels and axles would convert the simple construction project into a shopping project.

Most derbies allow "small improvements" to the wheels and axles, but not "big changes" to them. Improving the standard wheels and axles (e.g., polishing axles, smoothing irregular wheels) fits in well with the simple construction project. Using the original wheels and axles as raw material to create new wheels and axles does not fit in; that would convert the simple construction project for children and adults into an advanced machining project for adults.

Many derbies require everyone to use the wood block supplied in the kit, in addition to the wheels and axles. Some derbies require everyone to use the original axle slots, or to maintain the original wheelbase, or to use only certain lubricants. Some even prohibit lubricants altogether. There are many variations, depending on what different derby organizers think would change the nature of the project in an unfair way.

Support Innovation

A derby car is a creative project. While enforced rules are necessary to assure fair competition and to make sure that everyone is "playing the same game", it is good to allow creativity and innovation as much as possible.

For example, the maximum sizes we specify are as large as we can allow while still preventing cars from interfering with each other, with the start gate, or with the finish gate. Other groups are more restrictive. Some enforce maximum dimensions that match the size of an uncut block with wheels and axles mounted, even though their tracks could accomodate cars with additional decorations attached.

As another example, we don't restrict the choice of lubricant. Many excellent lubricants are readily available. Also, children can easily understand how lubricants work and that some might work better than others. A common complaint about "the mess" of liquid lubricants is at least as applicable to traditional powdered graphite, and messes are easily addressed with a "no transferable substances" rule that would also prohibit wet paint and similar problems. (You can test for "transferable substances" by rolling a car across a clean sheet of paper and gently wiping it with a clean cloth.)

To the degree possible, we try to make tools, supplies, and information available to everyone, rather than prohibiting them. For example, we have drill presses available at our workshops to help everyone create straight axle holes, we distribute a list of basic (and some not-so-basic) speed tips with every kit, and we make very good lubricants available at our workshops.

Other Expectations

Beyond the rules themselves, we have a few "unwritten rules", for example:

We do not bother including these expectations in our official rules. Likewise, our rules do not include our derby-night schedule or the details of our race method. However, for some derbies (especially larger/regional derbies), it may help to include such expectations and administrivia in the official rules, or in a companion document that is distributed with the rules.

Our Rules

These are the rules used by CSB 876 (Peninsula Bible Church, Palo Alto, CA). Note that these are just our local rules. They work for us, but are not official in any way.

See Also