Here's a quick setup for the wheel. Any wheel. It is designed to give the precise steering control, in the first 180 degree of throw. After that , the game applies a slight acceleration to the turn.
Wheel Turn = 220 (too low & it feels twitchy, too high and it's a lot of work)
Wheel Compensation = 1.00
In Options/Misc Analogue Smoothing = 0
First two are found in options/control
Don't forget to setup the same wheel turn in your controllers external program (ie Logitech Wingman).
In G25, in wingman, don't run the forces too high, they have a tendancy of burning out force motors if the forces are too high. 40% is good. I use 15% myself. A lot of people don't like spring centering, as they like to feel all the different force effects. Personally, I don't like that as it has no force in first 10-15 deg of throw. So I enable spring centering n set it to 60.
Don't forget to Allow Game to adjust settings.