How to set Disable Steering variable off in runtime? +other car related things

Hi. Im working on a car game and i figured out that when i leave the “Disable Steering” variable off in the wheel setup for back wheels i can do donuts easily with my car and i can also force some cool drifts like this. My problem is when i tried to setup some mechanics for this to detect when to set this value off for ex.:(when gas and brake is pressed at same time) i couldnt access this variable.

269271-disablesteering.png

there is no “Get disable steering” or “set disable steering” function.I only found this function for the simple vehicle, not the advanced one though.
Next thing is even if i was able to set this value in run time there is problem that the wheel handler would rotate the back wheels just like the front wheels and i dont want that. I want the effect, but not the animation.
So my questions are: How to possibly get/set this “Disable Steering” variable?
How to prevent steer animation on backwheels afterwards?