Crutches: Weight Distribution And Weight Transfer

The Way We Have The Weight Distributed In Our Race Car Can Tell Us A Lot About Our Setup




Coilover spring/shock combinations have adjuster rings on the threaded portion of the shock to set the spring height and regulate the amount of weight that is supported by each tire.




The cars that use stock springs have weight jacking screws at the front and rear that are mounted with a housing welded to the frame to adjust the height of the top of the spring. The top of the screw has a square hole to fit a 1/2-inch drive extension. A mark should be painted on one side of the screw so the number of turns can be easily counted.




This new coil spring adjuster system from AFCO allows the spring top to conform to the compression of the spring as the car negotiates the turns, providing more consistency.






For most short track cars, given a particular vehicle weight distribution, there is a low and a high range of crossweight that will make the car neutral. With the same springs, moment center locations front and rear, and so on, the car will be neutral at say 51.2 percent and at 58.6 percent. In-between is “no man’s land.” The truth is that we can find a certain percentage of crossweight in each range that will make the car neutral in handling.

A tool that facilitates changing springs and doesn't alter the weight distribution is this single-wheel scale by Intercomp. The weight is read with the old spring. Then, with the new spring installed, the jack screw is adjusted until the same weight is read.



This is how the weight should be distributed at midturn when we use the low range of crossweight. After the weight has transferred as the car negotiates the turns, the same amount of weight is supported by both right-side tires as well as both left-side tires. This is how it should happen with a balanced setup.




This is an example of how the weight would be distributed at midturn when we use the high range of crossweight. After the weight has transferred as the car negotiates the turns, the same amount of weight is supported by the RF and LR tires and the LF and RR tires would be supporting the same weight. The setup must still be balanced to achieve this result.




6. The car “snaps” loose just when the driver gets into the throttle.


When we change the front-to-rear percentage of total weight in the car, the crossweight needs to change to keep the car neutral in handling. This is a 2,800-pound Late Model with a 66-inch track width, a 56 percent left-side weight, and a 15-inch center of gravity running on a 12-degree banked track pulling 1.7 g's in the turns. The numbers in the chart were calculated using standard weight transfer dynamic formulas available in many books on the subject. The car is considered to have a balanced setup.


Weight Do’s:

Coilover springs are much easier to adjust when changing the weight distribution. Make sure there are no binds in the mounting points that will affect your readings. This mounting bolt needs a tapered spacer between it and the shock eye.

Some Weight Don’ts:
3. Don’t run the high crossweight range on high-banked tracks unless the banking falls off abruptly and there is a problem getting traction off the corners. And don’t try to run the low range on the flatter tracks with bite-off problems like I did at one time. That is how I learned about the different ranges.
5. Don’t try to match your crossweight to a competitor that is running well. His overall weight distribution and setup may be very different from yours, especially the front-to-rear percentage of weight. This setup stuff all works in combination, and each car’s combination is necessarily different.

Weight data is a part of that bundle of information about your car that you need in order to be competitive. Don’t be shy about experimenting with items such as weight distribution, and by all means, think outside the box.

Once you find that perfect combination that the car needs, you won’t share it, just like no one shared with you. Then you’ll know why it takes so long to be competitive. It takes getting to the point where you quit listening to your competitors and start thinking for yourself, no matter how long you’ve been racing.


Intercomp North Minneapolis, MN 800-328-3336