I agree 100% with the explanations and reasons for heel and toe braking. But there is yet another reason for using it that is kind of implied here but not really mentioned. It is also for the COMBINED reasons posted above - QUICKLY braking AND optimizing RPM simultaneously.
If you are coming aggressive and fast into a corner, you need more braking power than the higher gear offers. Heel and toe lets you maintain smooth 4 wheel braking while the clutch is in (no engine braking at all). 4 wheel braking keeps the car more stable and provides a quicker deceleration than just a downshift. Meanwhile the shift brings the car back into the powerband. As the car's speed drops, the brake pressure is reduce to nothing, and engine only braking starts to take over. Then you start to start to increase pressure on the accelerator 1/2 to 3/4 of the way thru the turn (depends on the geometry of the turn). You are in the lower gear power band and power out of the corner.
When you get it right, it works great, and when you don't get it right, it pretty much sucks. It is much easier to do on a bike, because you don't have to contort your foot to manipulate the brake and accelerator simultaneously.
Just my 2 cents worth.
If you are coming aggressive and fast into a corner, you need more braking power than the higher gear offers. Heel and toe lets you maintain smooth 4 wheel braking while the clutch is in (no engine braking at all). 4 wheel braking keeps the car more stable and provides a quicker deceleration than just a downshift. Meanwhile the shift brings the car back into the powerband. As the car's speed drops, the brake pressure is reduce to nothing, and engine only braking starts to take over. Then you start to start to increase pressure on the accelerator 1/2 to 3/4 of the way thru the turn (depends on the geometry of the turn). You are in the lower gear power band and power out of the corner.
When you get it right, it works great, and when you don't get it right, it pretty much sucks. It is much easier to do on a bike, because you don't have to contort your foot to manipulate the brake and accelerator simultaneously.
Just my 2 cents worth.