Threshold braking is a braking technique that requires an experienced foot. Thin soled (racing) shoes and delicate brake pressure control are necessary if youd like to perform this braking technique. Also being referred to as straight-line braking, it's one of the most fundamental skills to develop as a racing driver.
Threshold braking means utilizing the maximum potential of your brakes, or in other words, braking to the "threshold" of locking-up.
If youve read about oversteer & understeer, youve read that tires seem to work better when they are under a few degrees of slip. This does not only apply to steering (cornering), but also for braking and acceleration.
The trick for threshold braking is to get as close as possible to locking-up. By doing so you can achieve the maximum braking effort, allowing you to brake later and harder.
You will feel vibrations through the steering wheel, telling you where the point of locking-up is. If you feel you are about to lock-up the tires you should slightly reduce braking, while still applying sufficient pressure to remain in the threshold braking zone.
FINDING THE EDGE OF BRAKING CONTROL ISN'T EASY
If you do lock the tires you can hear the front tires sliding and will lose all steering ability. Tire noise is a great way to determine the effectiveness of your braking effort.
Screeching tires are good; this means youre using the maximum potential of the tires. Too much of that screeching noise however and the tires will obviously lock-up.
In case of ABS, threshold braking will become more difficult. Threshold braking with ABS is possible, but the system might interfere if it detects that you are getting too close to locking-up the tires. So your best option for ABS-equipped vehicles is to plant your foot on the brakes and simply leave it to the electronics. Of course the same rules still apply; you should still be smooth and be sensible with applying braking pressure.
Good threshold braking is better than current ABS systems, but it also requires a great deal of practice. I do not recommend waiting for an emergency to try out this technique. Practice it on the race track or find an open section of road without any traffic.