Have you ever had your car running great, had good speed, and the handling is "right on", then you change your tires and you find it just have the "punch" it did before? Then you've run into the dreaded "roll out" problem.
Not everyone knows that if the new tires you put on are a different diameter then the old ones are, you need to adjust your gear ratio to make up for the difference in tire size.
I've made an easy to use chart that helps you find what gear ratio to use to make up for this.
Here is a small piece of the rollout chart. It is written as a Microsoft Excel spread sheet. If you do not have Excel, you can download the Excel file reader here
In this example, we were running a tire diameter of 1.80" and a gear ratio 2.15. This equals a rollout of 2.629 (the first red square). We then changed to a tire diameter of 1.90".
To find out what gear ratio we need to change to, we follow the numbers under the 1.90 tire size until we come to a rollout figure that is close to what we had before the tire change. In this case, that number was 2.629.
By using the chart, we see that we need to change our gear ratio to somewhere around 2.25 to 2.30 to keep the same performance that we had before the tire change.
The chart that you download here is zipped, so you will need to unzip it then view it in Excel or the Excel viewer. You can then print it out on your printer so you can carry it in your pit box. The About RC Vehicles Roll Out Chart has been sized so that you can change your printer setting to size your printout to "fit the page" and it will printout nicely. There are two pages included, so make sure you print both pages.
Now, don't waste any more time, download the HobbyTalk Rollout Chart and get a jump on the competition!