They aren't attached to the servo horn, they should be attached the ball joint attached to your carb arm. I don't have my fail safes yet. The reason I tested it the way I did by turning off my transmitter is because this will simulate exactly what will happen if you're driving your vehicle the the Rx looses it's signal. The throttle servo doesn't become any easir to turn just because the Rx lost it's signal. So think about it. If the spring were to be strong enough to move the servo when the Rx lost it's signal, then it would also be strong enough to prevent the servo from opening the throttle at all when the Rx is receiving a signal.