Most RC car radios offer an end-point adjustment (EPA) setting that lets you control the exact limits of your steering and throttle.
The steering EPA is mostly used when setting up a car to ensure that the servo doesn't turn to turn too far.
For instance, when you first set up your car and turn the wheels all the way to the side, the wheels may turn all the way when you've only turned the wheel on your transmitter 75%. But, you want to be able to use the whole 100% of the transmitter's steering throw to control the wheels, so to do that, you would set your steering EPA to 75%. Now, when you turn the transmitter to 100%, the wheels will be turning as far as they can.
Once you set the end-points, then you would use the dual-rate adjustment to limit the steering throw (simultaneously on left and right) any further. Why would you do this? If you're on a wide open high-speed track, the car may feel too twitchy or sensitive - using the dual-rate adjustment, you can make the car easier to control by limiting the total amount of steering. Of course, this would make hairpin turns difficult, but the rest of the track would be easier.
The throttle end-point adjustment allows you to adjust the maximum throttle and the maximum brake separately. Normally you would use these when setting up the car to make sure the car's 100% throttle matches when you pull the trigger all the way back, and 100% brake matches when you push the trigger all the way forwards. For nitro cars, this will be most of the work, but for electric cars, you can then do more fine calibration with your ESC.