Scaling a car is easy with the right tools and may unlock secrets to handling and straight
The trickle-down theory states that if enough racers demand a particular part or tool, manufacturers will make a raft of them and the price will eventually become reasonable enough that a street car guy might consider spending a few dollars to go faster. Electronic weight scales are a classic illustration of this point. Three decades ago, only big-dollar Indy or NASCAR cars used expensive electronic scales to measure corner weights. We envied the teams that could afford such a sophisticated way of evaluating weight distribution in the car. While that method is considered essential for a road course or circle track car, the laws of physics don't change just because the car is only pointed straight. We thought it would be fun to look at how to measure weight to give us an idea of how that can affect performance and traction.
It's actually very easy to spend a lot of money on weight-measuring equipment, especially with the trick wireless systems now on the market. But the popularity of electronic devices has certainly contributed to a gradual softening in the price for basic hardwired scales. We discovered a set of scales from Proform that seemed attractive at less than $750. These budget scales produce the same basic information for much less than the high-dollar systems. And that makes it a Car Craft kind of story.
Playing the Scales
All electronic scales operate on the same principle. Place a sensor under each tire and it will indicate the amount of weight on each corner of the car. In the case of these Proform scales, each has a 1,250-pound capacity, giving the entire system a 5,000-pound limit. Each scale is made of lightweight aluminum measuring 14.5 inches long, 9.5 inches wide, and 2.5 inches tall. Four 20-foot-long cables connect the scales to the central display powered by four simple AA batteries, making the system completely portable. The digital display for this particular unit is simple, giving you a weight for each tire, a corner percentage, and a vehicle total.
The more expensive scales will calculate the left- and right-side percentages as well as cross weights automatically for you and display them on the screen. The Proform scale does deliver percentages at each corner, so all you have to do is simply add the numbers for left or right. As for determining the cross weights, the calculation is as simple as adding LF and RR, and RF and LR together for percentages or weight. These are simple steps you can do with a calculator and save a few hundred dollars in the process. To illustrate, let's keep the numbers really simple with the following quick example:
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The Proform scales come in this nice soft-sided carrying case that even has wheels. The sc
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Here's a tight view of the screen. The display indicates the weight as well as the percent
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Each cable and scale is marked and color-coded to ensure proper connection to the screen.
| CALCULATING PERCENTAGES |
| LF |
RF |
|
|
| 900 |
850 |
Total: |
3,150 |
| 28.5% |
27.0% |
Front: |
55.5% |
|
|
Rear: |
44.5% |
| LR |
RR |
Left side: |
50.75% |
| 700 |
700 |
Right side: |
49.25% |
| 22.25% |
22.25% |
Cross weight: |
LF/RR: |
1,600 pounds 50.75% |
|
RF/LR: |
1,550 pounds 49.25% |