Q: “I am very comfortable using left-foot-braking and have found many situations where it seems to be an advantage, but other than lap times, how can I know if I’m really using left foot braking too often or too much? I switch between right and left foot, depending on the corner, and sometimes I feel that I over-slow the car when braking with my left foot.”
A: You’re not alone in sometimes over-slowing from left foot braking. Because it’s usually not as well-trained and sensitive as our right foot, it’s easy to apply just a little too much pressure. Of course, you’re right that it can be a big advantage in some places, too. If you could drive on the track every week for a couple of years, for sure your left foot would be more sensitive and you’d be even better (wouldn’t that be a shame to have to drive that much?!!!).
How can you tell if you over-slowed? What does the engine sound like as you go back to power? Can you tell from the engine note whether you over-slowed and now the engine is bogged down a little? As you come out of the corner, can you check your RPMs or speed, to know whether you over-slowed? If you have a data system that has a predictive timer, then you can tell if you’re plus or minus on your best lap time. You can look at data after the session (but that’s too late sometimes). You can have someone take segment times (but again, you usually don’t know the results until after the session, unless that person is on the radio to you and giving you immediate feedback).
Figuring out if you have excessively left foot braked ASSUMES you already know (sic. already have NAILED) the optimum Right foot braking speed for the corner. If you don’t have that speed nailed you will not (easily) be able to optimize the corner for left foot braking. Once you have the right ft figured out you will be able to feel when you reach the ‘dance in your pants’ you get with the increased sense of balance the left foot brings to the equation. And of course as Ross says data will be able to help you see what the gains are.
The number one reason for a driver to use improper level of LFB is trying to learn LFB too early. If you have not gotten right foot braking down to an art such than you can feel when you are even a MPH or 2 off optimum corner speed at, at least, all 3 major points in the corner, then left foot braking will be sorcery. At east for most people.
Driving an automatic car for both track things and daily use, as soon as I put a good seat in it I started left for braking at all times. It’s definitely not the same as driving on a track every week for a few years but it is a considerable amount of practice. As long as I make a conscious effort to practice fine pedal control, I think could could get at the least very close to right foot sensitivity. Perfect practice makes perfect?