Dead zones, are settings for your controller, that define how much input they require, before they register it. If your dead zone for the trigger is 20 then your trigger will not react, before you reach 20%.
This is great if you have an old and worn controller, that is not as precise as it used to be. It can correct twitches or that slight turn towards one side on the straights that controllers can have, when they get too worn out. By default though, Forza 6 has some pretty high dead zone values that limit your input range as well as how sensitive you can be with brakes, throttle, steering etc.
There are two settings for each input, called inside and outside. Inside dead zone is the amount of unused trigger pull at the end of travel. Outside dead zone is the amount of unused trigger pull at the beginning of trigger application.
Basically you want the inside value to be as low as possible, and the outside as high as possible without it feeling uncomfortable. Ideally, inside dead zone should be 0 and outside should be 100 but there is a reason why dead zones are there. You’ll know that you’ve overdone it if your controller registers inputs, without you giving it any. So if you are on a straight, and you car turns slightly to one side, you’ll need to adjust the dead zone for steering. If you can see in the telemetry that you are applying a little throttle or brake even though you don’t have your fingers on the triggers, you’ll need to add a little dead zone to those.
Change dead zone settings to 0 for inside and 100 for outside.
Optionally leave steering at 5 for inside if it feels too sensitive
Adjusting dead zone to 0 or 100, will give you a larger range of input, and allow you for a more delicate car handling. This in return, and if used correctly, will allow you to attach corners better, apply more controlled braking and generally go around the track faster.