What is meant by the term 'threshold braking'? -- Patrick D.
I reached out to Colin Caissie, lead instructor at Pinnacle Advanced Driving Academy for support on this answer, as my racing skills unfortunately fall into the "amateur" category.
On the street, most modern cars have anti-lock brakes (ABS) that manage and prevent wheel lock-up electronically. Previous to this, threshold braking was introduced to new drivers by teaching them brake-pedal feel, how to modulate and pump the pedal to scrub off as much speed as possible before locking up the tires.
Threshold braking is now a term used mainly in motorsports. New track enthusiasts approach a corner mildly, lightly applying their brakes, while the experienced driver will approach the same corner braking later and harder. The purpose is to use as close to 100 per cent of the available grip of the tires to slow the car in the shortest distance possible, thereby shaving time off the clock. The point at which you apply just the right amount of pressure on the brake pedal is referred to as the threshold. Applying too much pressure exceeds the available tire grip, causing them to stop rotating and lose control.
Threshold braking can be a difficult skill to master, and some will argue it is not relevant with newer ABS systems. But ABS brakes are reactive, reducing brake pressure to prevent wheel lock-up, which countermands the maximum-pressure theory. Somewhere between the two is where you will find advanced drivers looking for that competitive advantage sweet spot.
Lou Trottier is owner-operator of All About Imports in Mississauga. Have a question about maintenance and repair? E-mail firstname.lastname@example.org, placing "Lou's Garage" in the subject line.