I thought about this for a second and I can't see why this wouldn't be possible to have a dial/slider or something because lets say I wanna drive normally I'd like close to a 50-50 but for a rally set up maybe 40-60 or something to help me take wider turns by adding a over-steer tendency to the cars brakes Ie: Covet hatchback
Just open the hatch_suspension_F and hatch_suspension_R files and search for "brakes" and you'll find them. There you can set the brake power under "brakeTorque" and I'm pretty sure you can just put in different values to make a different balance. For example the hatch stock has 850 front 450 rear so that would be 65/35-ish I think. Correct me if I'm wrong though -- edit: I think you could even copy the brake setup and paste it underneath, then name it different and give it different values, and it should show up as a seperate option in the parts menu.
Yes, the brake bias is set in the .jbeams. It's between 60/40 and 70/30 for real cars depending on weight distribution and other factors. Consider that most cars are front-heavy, and when you brake, a lot of weight is transferred to the front, so the front brakes do the majority of the work. I know on my 2008 Maxima the rear brakes are 1/3 the thickness of the front brakes. It is certainly possible to code a brake bias/torque controller in Lua, but that would only be for high-end racecars.
my old buick century would lock the rear drums before the front discs. Lots of brake bias to the front is good