Sorry for late response, busy week - thanks mate for your thoughts, however the issue is that wheel-locked and skidding vehicles out-brake ones using ABS.
Most "realistic handling" mods are nothing of the sort - they 'sculpt' each vehicle's handling in a top-down way, enforcing the handling specifications irrespective of one another using artificial and physically inconsistent values.
The physics engine supports much more realistic handling than most people seem to realise, where the handling's determined in a bottom-up way, ie. cornering ability becomes a function of lateral friction and a properly-functioning suspension system controlling the weight distribution, rather than inputting a physically-inconsistent and much higher lateral friction value that approximates the specified cornering ability but regardless of whatever the suspension's doing, or not doing..
Ditto for all aspects of linear accelerations - the "low speed friction modifier" that causes wheelspin at low speeds - what the hell kind of physics would cause that? It's Tonka physics. Zero that shit. Wheelspin should be purely a function of the current and dynamic balance of grip and power. Likewise, "flat-out velocity" is the speed at which aerodynamic drag balances against engine power as a function of the gearing ratio, road gradient, wind effects (if enabled) etc., and the engine in question won't necessarily be redlining at that speed - peak torque for an old V8 for example's likely to be nearer the middle of the rev range.
And so also for stopping power - it should be determined by the same friction and suspension-dependent weight-distribution factors as everything else - for instance, most vehicles should have sufficient braking power to be able to lock their wheels at almost any speed. But if you brake progressively instead of suddenly, you shift the weight forwards, compressing the front end, and so can brake ever-harder without causing a lock-up until the last moment..
You then further tune the brake balance at that point, to control which axle locks up first - obviously, if it's the front-end then this exerts a strong yawing tendency under heavy braking, as the rear end scrubs off momentum more slowly than the front, thus converting linear momentum to angular. Ideally, you want simultaneous lockup on both axles, with maybe a slight rear axle lead (so you can still steer up to the last second).
It is only THEN that you enable ABS, if that's what the car should be fitted with...
So the binary flag for vehicles with no ABS is "0". The old pony cars, most of the classics etc., have no ABS.
The standard ABS, option "1", applies a constant ABS to all wheels independently, in ms timeframes
Option 2 means "optional" - ie. it was an option on whatever RL car it's modelled on, not a standard fitment. So for example the Karin Sultan would use this setting. Some will spawn with ABS, some without. Applies also to your saved cars - you might have to respawn one a few times to toggle ABS on and off (someone should do a key toggle mod, cough cough IKT).
Option 4 is a different kind of ABS, sampling the wheels one-at-a-time at much lower frequency (about 50 ms). Hence the wheels alternately spin and lockup in a left-to-right, front-to-back sequence, causing a weaving effect and instability.
Like option 2, Option 8 fits option 4 ABS to 50% of spawns at random.
So the values to use are 0, 1 and 2. But the whole raison d'etre of "1" is that it should out-perform "0"... yet it's 30% worse in every case.
Some people have tried modding materials.dat to globally reduce friction values in the attempt to get realistic (ie. fun) handling physics - i've tried it too but it's unnecessary and kludgy, with dubious results - you only need to input self-consistent values into handling.meta to get naturalistic handling. But as i say, uniformly lowering friction has no effect on the ABS performance - overall stopping distances increase, but ABS stops still need 30% more distance.
So the only logical explanation seems to be that there MUST BE a "skidding friction" modifier in action when a moving wheel locks up. Because if it were simply the linear friction value, then lowering it enough would eventually give ABS the advantage.. yet it does not.
This modifier is obviously THERE, since we see its effects - yet it's not a vehicle-specific parameter...
..so it must be a lower-level setting, in the Rage physics engine? Dunno.
Like i say, editing materials.dat is useless, likewise tyre effects. Dunno where else to look.
It's a shame, you can have awesome sim-like fun handling, but for this one fly in the ointment..