The load is your rc car. It's the power the motor takes to spin up the drive train and get your car moving. You have a high load starting off from a dead stop. As you gain speed the load decreases. When you brake with your motor the load increases again. You can estimate loads with some math or use a datalogger but it's not really necessary. It's nice to have a ballpark idea sometimes...

Try try and estimate the load, check this out: https://sites.google.com/site/tjingu...age-amps-watts