Proper ballast placement is actually a free speed secret.
Getting the ballast located correctly is a key component for a faster race car and will allow you to go faster around the turns and provide more grip for your car. So, in conjunction with Rebco, we’ve put together a few simple tips for ballast placement.
Lose Weight First
First, you should be very weight conscious when constructing your car. Be sure to look for any opportunity to save weight without compromising safety. You will be amazed at how little things can add up to big weight savings. Here are a few ways you can reduce vehicle weight:
- Consider using a fiberglass or carbon fiber hood, bumpers, and other body components
- Avoid or eliminate unnecessary interior items–sound deadening material, radio, A/C, window cranks, etc.
- Eliminate extra engine accessories–A/C pump, steering pump, etc.
- Use stainless steel headers instead of cast iron
- Consider using lighter Lexan windows instead of glass
- Choose an aluminum radiator
- Remove the seats and use a lightweight plastic or aluminum racing seat
- Choose lightweight wheels
We’ve even seen people go as far as drilling lightening holes in the center of bolts to shave weight. Remember, every little bit adds up but safety should always be the first priority.
Check Ballast Rules and Specifications
Once you’ve reduced vehicle weight, you’ll need to add ballast to get the car up to the minimum standards set by your sanctioning body. For example, circle track racers should check their rulebook for the maximum left side weight allowed and get as close to the maximum left side weight allowed while maintaining the minimum total weight. You should never run your car heavy for the sake of more left side weight.
Next, check with your car builder for his recommendation on front-to-rear weight percentages. Verify that your car is “race-ready” excluding the ballast operation. Now that you know what you want for rear weight you can begin finding a home for the ballast.
Ballast Placement Tips
You need to locate the ballast as close to the car’s center of gravity and as low as possible while meeting the minimum total weight rule, car builder recommended rear weight, and any left side weight restrictions. In other words, you want the ballast to be located in the smallest area possible. For example, let’s assume your car weighs 2,500 pounds race-ready but without any ballast. We’ll also assume you have a 200-pound driver, your minimum weight allowed is 2,900 pounds, your recommended rear weight is 50 percent, and your maximum left side is 56 percent–a common scenario for circle track competition. With these assumptions you will need to add 200 pounds to get up to the minimum weight. In this example, we’ll also say your car has 50 percent rear weight without any ballast installed.
Since we are starting with a rear weight percentage that matches our car builder’s recommendation, we need to add 200 pounds of ballast to reach our goal of 50 percent rear weight at the rules-mandated 2,900 pounds. When mounting the ballast we want to concentrate the ballast in the smallest possible area to make the car go faster.
Why is important to mount ballast in a small, concentrated area?
Let’s picture a simple example: a playground teeter-totter. The teeter-totter’s pivot point, which is located in the middle, is comparable to the center of gravity in your race car. Now picture 500 pounds of weight on both seats of the teeter-totter (the seats compare to the left and right frame rails). In the static position, the 500 pound weights would balance out; however, when you put the teeter-totter in motion that much weight would require much effort to get started and even more effort to stop once it got moving. If the teeter-totter were moving fast, you would be crushed trying to stop the movement with 500 pounds out on each end. In your vehicle, your springs and shocks would have to control all this dynamically moving weight rocking back and forth. Front-to-rear movements would have to be controlled as well.
Now picture the same example with the 500 pounds from each seat moved directly over the pivot point (this would be the same as our center of gravity in our race car). You would notice that the teeter-totter is still balanced, but the 1,000 pounds of weight is carried directly at the pivot point. When put into motion, the teeter-totter is going to be much easier to control compared to the spread out version that had the 500 pound weights clear out on the seats.
Just think of how much easier this situation is on your springs and shocks!
Going back to our example above, we would want the 200 pounds of ballast to be mounted in a concentrated area within the car as opposed to splitting the ballast between the front and rear of the car. As our teeter-totter example illustrates, you’ll reduce the amount of weight that has to be controlled once the car is in motion by concentrating the ballast in one small area. You’ll also reduce the amount of back and forth motion in the turns and front-to-rear weight transitions under braking. Weight transfers will occur in more controllable amounts, which will result in a more efficient and stable handling race car. Keep in mind, the example we used is more typical for a circle track setup; in a road race vehicle, you’ll likely be shooting for a more balanced left-weight percentage of 50 percent (although that is not always possible due to driver offset).
Following this principle, you should take the time to build proper ballast brackets between the frame rails to achieve the desired weight distribution using the smallest concentration of ballast as possible. Strive to keep all support items as close to the center of gravity as possible. Batteries are heavy and need to be located just like ballast. For example, in a circle track car, you should mount your battery as well as tanks, electrical items, fuel filters, hoses, drink bottles, radio boxes, or any support items to the left of the center of gravity.
If you are conscientious mounting all of your racing components, you will be able to place your ballast closer to the center of gravity and low to the ground while still maintaining optimum left side weight and desired rear weight. Your car will be more nimble and responsive, tire temperatures will be reduced, tire wear will be improved, and lap times will go down.
And victories will be on the rise.