The amount of steering angle really doesn't mean anything. What matters is that your endpoints are set such that the servo doesn't whine or bind at 100% steering throw in each direction, so that you don't burn up the servo. With that said, you more than likely won't use all of that travel anyway. That's where your dual rate comes into play to reduce the amount of left/right travel equally. For indoor tracks, we generally set the dual rate so that we have a turning circle of about 5.5 to 6 feet diameter.
Any more than that, and the steering will seem "twitchy" and will be harder to drive, since you have to manually control the limits using steering input. If you have your dual rate set correctly, you can just crank the wheel all the way and have the correct turning radius.
For 1/12 scale, we use about a 3 - 4 foot diameter circle. For both scales, these circle diameters are dependent on the size and layout of your track.
You should also check the circle diameter in both directions to make sure that they are the same, or the car could behave erratically. In addition, it is good practice to check this before every run, in case something changed due to a crash, servo issue, tweak, etc.
*** The Gate - Celebrating 7 years at the same location ***
The difference between genius and stupidity is that genius has its limits. - Albert Einstein
Understeer is when you hit the wall with the front of the car and oversteer is when you hit the wall with the rear of the car