Your car should not exceed 7 inches in length.  That includes any toys or fixtures you may want to add onto the car for decoration.  So when designing the car make sure you take that into account before cutting your block of wood.  But it CAN be SMALLER than 7″.  There is a slight disadvantage if you are less than 7″ in length.

The car should not be wider than 2 3/4 inches.  The block you receive is 1 3/4″ thick.  So this rule pertains to those of you who plan to decorate with fenders or whatever else you can think of.   At the same time, the wheels should be at least 1 3/4 inches apart.  To measure this, flip your car upside down.  Measure the distance between the front two wheels from inner most part of the wheel to inner most part of the opposite wheel.  Repeat for the back side.   This is especially important for those that have learned that wheels that are closer together gets a better ride.  The easiest way to make use that you fit within these dimensions is to make sure that a standard block will fit between the wheels once your car is completed, no ruler necessary.  Quick and easy test

And the last part of the dimension rule is that there must be 3/8 inch clearance from the bottom of the part body and the track.  Most of the time this comes into play if you have those bottom lead plates that screw or glue on the bottom of the car.  So if you are using that type of weight, it might be best to make sure to measure this distance prior to race day.  If you drilled your own axle holes, be sure to check this as well.    The placement of your wheels could be too high on the block which could cause your body not to pass this requirement.

There are a few good concepts out there that will increase the overall speed of your car.  Low profiles, slim profiles, profiles with less drag seem to always place.  Body design does play a small role into the overall performance of your car.  If you have a bigger car, try and hollow out as much as you can so that you basically have a shell.  This will allow you to adjust the center of gravity to get the most out of your car design.

There is this big thick pinewood derby physics book out there that will tell you that 4 wheel car will be faster than a 3 wheel car.  This statement is simply false.  A 4 wheel car is MUCH harder to tune as well.

From my experience, and what you see on the winner’s circle, 3-wheel car designs are the fastest out there.  If your rules allow this modification, I highly suggest this route.  The “high wheel” will be the wheel opposite your steering wheel in the FRONT.  A properly tuned car will turn towards this high wheel while traveling down the track.

Be sure to take the time to tune your 3 wheel car, otherwise it is a pointless modification.

As far as speed goes, I once thought that drilled axle holes were faster.  Since we came up with treadmill tuning method, I have come to the conclusion that it really doesn’t matter as far as speed goes.  They both have about the top same speeds.

Where I have noticed the difference, is tuning.  RARELY is a BSA slot perpendicular to the body.  There is always some sort of angle.  With each block having 2 slots, the fun begins!   Derby Dust now offers CNC milled BSA slot blocks that fix this problem.  Again another industry first.

With a properly aligned vise, one can drill axle holes with a drill press.  BE smart.  Make sure you are drilling 90 degrees perpendicular to the body.  Or with the purchase of a drill guide, one can do it with hand drill.  DO NOT attempt to drill holes by hand without one of the specialized drill jigs.  Just be sure that the jig is flush with the body to ensure a perpendicular pilot hole.