Ziggy's Gear Charts

Ziggy's advanced gear charts help you get the most from your Ziggy's engine under a variety of track conditions by allowing you to tune for maximum performance. The traditional quarter midget gear charts are organized as a grid making it difficult to determine the ratios that are "close" to your existing gearing. The advanced gear charts list the gear ratios in increasing order allowing you to easily see the ratios of interest. In addition, the charts also lists the equivalent tire circumference change and the approximate RPM change for a given engine type.

There is really no secret to gearing. Using a larger ratio will make the engine go faster at a given speed, and using a smaller ratio will make the engine turn slower at a given speed. The trick is to know how much change will result from a given change in ratio. The Ziggy's gear charts let you know what to expect with each change. This lets you dial your car in quicker or compensate for another change in the car or track. The stopwatch is still the final word on gearing, however these charts will help you get the job done quicker.

The chart has 3 main columns, Ratio, Delta RPM and Tire inches as shown in figure 1. The ratio column is self-explanatory, it lists the ratio between axle and engine RPM. The Delta RPM is the change in RPM that you would expect if you changed from "Ratio 1" to "Ratio 2". The tire inches if the tire circumference change that would give you the same effect as changing from "Ratio 1" to "Ratio 2". Remember the Delta RPM and Tire inches column always refer to the effect of changing from the ratio in the previous row.

Figure 1

How do I use the Ziggy's gear chart?

Here are a few examples:

Back

Find a close ratio

The ratios are listed in numerical order. This allows you to quickly see ratios that are close to the one that you have or close to the ratio that you are considering. Let's say you want a 4.84 ratio for your Honda, which requires a 31 engine and 25 axle gear. The problem is you don't have a 25 tooth axle gear. No problem. The chart in Figure 2 shows you could also use a 4.83 ratio using a 36 engine and 29 tooth axle gear. This puts you back on the track quickly.

Figure 2

Back

Changing Tire Circumference

Let's say you are running an 18/31 ratio in your B-mod and a Firestone with a 35.5" circumference and your RPM is where you want it. Now you change to a Dunlop with a 35" circumference but keep the RPM the same. What gears should you use to keep the same RPM?

Figure 3 shows the process. The 18/31 gears gives a 9.87 ratio. The the tire column indicates that the difference in tire circumference between this ratio and the one above is 0.16". We are looking for 1/2 or 0.5" so we simply have to go up the column. If we go up three rows we get 0.16 + 0.17 + 0.12" = 0.45", which is close to 0.5". The new ratio is 9.74 which is 3 above the original. We would use 20/34 gears.
Figure 3, Tire Circumference example

Back

Changing RPM

Let's say you are at a new track with 20/31 gears in your Modified and after your first practice you are 200 rpm low.

Figure 4 shows the process. The 20/34 gears gives a 9.74 ratio. The RPM column give the expected RPM change between the current ratio and the one above it. Going down one ratio (higher numerical ratio) only gives a 33 RPM change. We need 200, so we have to go several ratios. Going down 4 ratios will give 33 + 47 + 44 + 81 = 205 RPM. This means use the 19/33 gears.
Figure 4, RPM Change Example

Back

Is it better to run big gears or small gears?

Gears are gears are gears! For example, on a Deco you could run a 20/24, 25/30, or 20/36 engine/axle ratio and they would all give you a 6.88 final ratio. No matter which ration you use the engine will go around 6.88 times for every time the rear tire goes around. It will be exactly the same for each so no combination have more torque off the corner or more top speed. They are all the same.

That said, there are some subtle differences between large or small gears. Small gears are lighter and are a little more tolerant of an angle between the axle and engine. Large gears will wear slower and cause less bending of the chain. Larger gears will also give finer increments of overall ratios. Make your gear selection based on the ratio.

Back

Gear Charts

The gear charts are formatted in Adobe Acrobat format. Simply click on the link and them print the chart out. Note, there is a different gear chart for each class of Deco cars to best match the target RPM for that class.

Back to Ziggy's Home Page

Copyright © 2007, Ziggy's Motorworks, All Rights Reserved.