I dont know what spring you're using then... my spring has put my car to brakes because of dead batteries many of times, I never run a failsafe, and I probably never will. Atleast for my car a trs is more than it needs.
If my car has an engine in it, it is gonna have a spring... one day I was taking my car apart for cleaning, and I accidently streched my trs[&:]... that week I had 4 runaways... I decided not to run my car until I got another return spring. I got another and have not had a runaway since...It was probably mainly bad luck, but I'm am not going to take the chance with my new motor...my old one was totaled before my 4th gallon of fuel, the piston could fit all the way through the sleeve... because somtimes the runnaways were so bad I lost site of the car as I was running after it, then find it upside down with the engine stoped...