Article 2 “Understanding Wheelbase”
Wheelbase has profound implications in the term of vehicle handling. It dictates much how well the truck will accelerate and turn, and it can be changed to suit a particular driver and track conditions. Here’s how to tune the wheelbase so you can optimize it for your track and driving style.
WHAT IS WHEELBASE?
The wheelbase is the distance between the center of the contact patch of the front tire and the center of the contact patch of the rear tire. This is easy to measure on an RC car with a tape measure or machinist’s ruler. To get an accurate measurement, make sure to turn on your car and radio so that the steering servo is centered at your normal trim position. Having your ride height set properly also aid in giving you an accurate measurement of wheelbase. On most RC cars, wheelbase changes are made by moving shims on the outboard pivots of the A-arms. Thus, it is less important to know the specific measurement than it is to know how the shims are arranged if you are keeping track of it on a setup sheet.
IN THE TURNS!
The cornering performance of a car is dictated in large part by the wheelbase length. A car with a longer wheelbase will be more resistant to rotating through a corner, while a car with a short wheelbase will rotate faster in a corner. On a tight track or a track with a lot of grip, it may be advantageous to run a shorter wheelbase to get the truck to rotate better in the center of the corner. On a long track with mostly wide corners or a slick track, lengthening the wheelbase will keep the truck stable so you can use more throttle for faster cornering speed.
OVER THE BUMPS!
Loose or tight handling issues like this can be addressed by changing the wheelbase at just one end of your short course truck. If you move the shims to make the wheelbase longer at the rear of the truck, the static weight on the tires ( if measured with scales ) gets heavier at the front which will make the truck feel tighter. The opposite is also true. If you’re consistently fighting a specific handling condition, it is worth trying to change it during your race preparation at home.
Wheelbase changes can also be made to affect the forward bite. On a 2WD truck, shortening the wheelbase will help transfer more weight to the rear tires under acceleration. His will help the rear tires dig into the track and also help with forward bite. On a 4WD truck, the answer is not as obvious. Since all four tire are being used to accelerate a 4WD truck, more weight transfer to the rear of the truck will serve only to make the front tires less effective. Lengthening the wheelbase on a WD will keep he tires loaded more evenly during acceleration which will help overall acceleration. It will also be more stable on corner exit with the front tires doing more of acceleration work.
Changing the wheelbase is another tool to make the truck handle and accelerate better. Build your kit with the stock wheelbase option, but make some changes during practice sessions to see if you can get a handling and acceleration characteristic that better suits your track and driving style.