Complex sentence: Drivers had the option of turning the freewheel off through a switch under the steering column to benefit from engine braking, which was useful when going down a long hill in hot weather for example, since the front brakes were prone to overheating and fading.
Split into simpler sentences: Drivers had the option of turning the freewheel off through a switch under the steering column to benefit from engine braking. Useful when going down a long hill in hot weather for example, since the front brakes were prone to overheating and fading.