This is no secret to seasoned builders.  Weight placement plays an important role in how well a PWD car will perform.  There are numerous scientific equations that will explain the science behind this.   Simply put the more weight you can shift towards the rear of the car, the more “potential” energy it will have.  The key important term his is POTENTIAL.   It is believed that the more stored energy you have, the faster your car can travel.   However, the PWD world has been proven that COG (center of gravity) is the more important than shoving all the weight in the rear of the car.

What is COG?  It is an important function in building a pinewood derby car.  COG is the balance point of your car.  This will be measured by using the ruler.  There is a COG tool on the market for those that like to spend a few extra $$$.  I’ll update this once I find it again.  WHY is COG important? Putting weight randomly on your PWD car is not the key to getting the most out of your build.  Center of gravity placement should be between 1/2-1″ IN FRONT of REAR axle.  This is true for all wheel base types whether you are using a standard wheelbase or an extended wheelbase.  This has been determined not by mathematical formula, but by the PWD junkies with thousands of builds underneath their belts. I have tried to prove them different, and just came to the same conclusions as they have.

Take notice on one particular detail.  TYPE of WEIGHT.  It will not matter if your weight is lead or tungsten to achieve a fast car. Do not listen to the hype.  Tungsten does not make a car faster.  Weight is Weight.  The maximum weight is 5 oz.  COG does not care whether it is wood, steel, lead, or tungsten.  Before spending all your available funds on just weight, please understand this statement.   FOR all my builds, I use lead as primary weight.   Weight pocket (meaning how big a hole is drilled for lead) depends on car design.  Small profiles will need larger pockets to offset their reduction in wood weight.   For final weight,  I drill a single 3/4″ forstner hole about 3/16 ” deep just in front of the rear axle.  I add the remaining tungsten putty throughout this hole to properly distribute the weight according to its balance point.

This balancing point (COG) will differ from car to car due to design, type of weight, type of wood, etc.   The first thought that comes to mind is that the most potential energy would be a weighted rear bumper.  This will not give you the fastest car.  (Actually this type of weight placement will give the car too much “push” and will cause your car to fishtail (move side to side) down the flat of  the track. Putting the weight on the front, although gets you a slightly quicker start down the curve, does not prove to be the best weight placement for the remaining flat portion of the track. The closer to a 1/2″ COG (in front of rear axle), the more potential for a faster car.  From my experience, the closer the COG to the rear of the car, the more time it will take to tune it to its fastest speeds

For your first build, I suggest a 1″ COG in front of your rear axle.  It will be the easiest to obtain.  It will give you a more stable ride, will require less tuning time.   Unless you have built the same design over and over, it might take some time tuning the COG.  For a preliminary run at things, cut out your body.  Sand it to near final sanding.  Drill out the holes for you weight.  If you are using the solid “plate” lead weights, it will be more difficult to distribute weight to obtain the proper COG.  I’m not a real fan of these as they have a lot of ZINC in them to make things shiny and it takes up a lot of surface area to use.  I am a big fan of 1x 3/8″ hole drilled behind the rear axle, with 2x 3/8″ holes in front of the rear axle as close as you can get them.  Then adding 1/4″ weights.  If your build can accommodate 5/8″ holes, that would only require a hole in front of and behind the rear axle using 1/2″ weights.   Once you have the balancing act close, then finish the car, add the wheels, and then fine tune your COG with tungsten putty.  The tungsten putty is added to the bottom of the car via drilled holes.