Larry Herman

I sure hope that he wasn't a "hands-on" instructor!

Bob Rouleau

Bill - PCA policy (at least in the National Program) is to inititate so as to transfer weight without risk of lock up and rapidly but progressively build up to threshold braking, finishing with a soft release of the pedal to avoid upsetting the balance of the car. The idea is to transfer weight and increase the front contact patch before extracting maximum braking performance - exactly as m75 mentions, i.e. avoid jumping hard on the brake pedal which involkes ABS or lock up if there is no ABS.

As to stopping the wheels six times per second, that sounds like either ABS, or a bumpy track which makes perfect threshold braking very difficult since the wheels bounce and unload. Ideal threshold braking never stops a wheel since sliding a wheel even momentairily increases the distance required to atttain the correct entry speed.

Best,

mrbill_fl

here it is: http://www.redlinerennsport.homestea...13Braking.html

Chicago Region Porsche racer and tuner John Ruther (Northstar Motorsports) wrote an article a couple of years back called "Don't Brake Backwards." The message is one that seems incredibly obvious after reading the article, yet rather illusive and typically overlooked until ruminated upon. Many drivers, not having fully explored their or their car's capabilities, have a
tendency to brake harder as they approach the turn in point. He offers that a driver should perform maximum braking early in the braking cycle, gradually easing up as turn in is anticipated. This has several benefits.
First; it gets heat in the brakes in a hurry, which increases their effectiveness. Second, it levels or even lessens the accumulated heat stress in brake components by progressively easing their burden as total braking time increases. Third, it allows the car's suspension to start to level off as the turn-in point is reached, increasing cornering stability. A good concept, no?
.....
from: Driver's Ed. Education - A Series of Specifics for Success by John Hajny




Sooo,
the main point is weight /balance transition after braking is done thru turn in? (Correct ?), which is really beginning of trail braking concept?

I'm ok with that... but had a problem w/ what sounded to me like coasting... when I'm trying to stop transmission braking...
In reality, if the braking point is deep and consistent theres not much coasting.... just focus on the transistion and being smooth on turn in and gas.

Thats good for the pits, but its a lot to cover in the car...
If I understand correctly.......

but.... I'm more likely to be yelling "Don't give up on the brakes, when you go to the clutch!" lol!


-oh, the spec racer threshold braking was like 4-6 micro second lockup's over 3 car lenghts, scrubing 120 to 45(?) mph, so amazing I still remember it.. looked like slow motion. or a prop blade (strobe like) (also as described in johnH's article)


(ps:I missed the * in LH's post, thanks for pointing it out!)

Dr.Porsche

If I have a student that is having trouble with the "Number System" Or is not grasping the "How hard... at what point in the braking zone question", I will tell them that I will squeeze their arm like I want them to "Squeeze" the brake pedal. *I only do this with someone who is somewhat comfortable and not too anxious on the track* I will wrap my hands around their bicep and squeeze to emulate the braking. Obviously this would not work for trail braking (Trail braking is not for the novice imo) I have had really good feedback from this, and no one gets freaked out or feel like they are not in control. This works especially good into a turn 1, long, STRAIGHT braking zone.

Larry Herman

That sounds like a great technique! I am going to try it with the next student that doesn't get braking.

One other item that I usually discuss with students is that most street drivers are reactionary in braking; i.e. they press on the brakes, and if that is not slowing the car enough, they press on them harder. As a racer/track driver you need to be proactive with the brakes. You need to know how much pedal pressure produces how much braking force. Then, by judging the speed and distance remaining, know how much braking that you need in order to slow the car. It is just like steering, in that most of us have learned how much steering produces how much arc, and then by looking at a turn, can pick the correct amount of steering input for the initial turn-in.

RedlineMan

Geeeez...

I was just gonna say that!

I think this is essentially what Larry is saying, and quite well as always. IF you can brake in this manner, and can initiate the turn in somewhere near the last third of the sequence, then you are pretty well optimized for time & speed. If you brake like this and ease completely off before turn in, you are braking too soon.

The upside is (along with the ones I listed in the article), unlike someone waiting till the end to brake hard, you likely will not be in a panic situation because you don't have room left to brake hard, late. If you brake hard early, and ease up as you go, you will know sooner whether you've braked too soon, just right, or too late, and might have more time to deal with it if you've flubbed.

Doc V.

Skip Barber Racing School instructors advise students to begin with a 7 pedal and to increase pressure quickly from 7 to 10 (with the "10" designation referring to the threshold of lockup). The instructors consistently emphazie that effective braking involves (i) losing speed quickly and (ii) losing the right amount of speed.

JCP911S

Braking technique varies depending on the turn. As Larry points out, "threshold" braking becomes more appropriate as the amount of speed reduction increases.

Bottom line, braking creates weight transfer... the degree of weight transfer from braking should be identically matched to the degree of weight transfer that occurs from turn in. "crushing" the brakes going into a high speed sweeper causes too much compression of the front suspension and will destabilize the car.

Generally speaking, regardless of the degree of braking, the brakes need to be released as the car turns in, so the car should be at maximum braking at turn in, and that should end as soon as the wheel is turned.... but that "maximum" must be the maximum for that turn... not the maximum braking the car is capable of.

JBH

It most definately depends on the turn or maybe more descriptively, how fast you are going when you start braking and how much speed you need to lose to get into the turn. Think about it...you can brake very hard with no threat of lock up when traveling 140 mph. That pressure must be released as the car slows down or the wheels will lock.

The last thing you want to do is apply most of the pressure at the end of the straight just before turning in - odds are you will lock the wheels, imbalance the car and spin off course.

Larry Herman

Exactly! Just because the car has unbelieveable brakes does not mean that you need to use all that ability every time you touch the brake pedal.

As a corollary, I avoid brake pads with "high initial bite" or "good torque values". I can generate enough "torque" to bend the brake pedal. I want pads with good modulation, linear feel and good release properties so that I can use them as accurately as I use my steering.

M758

This comment reminded me of race braking. If you are trying to race and outbrake some into a corner or are forced on the inside line you can use this style of braking to great effect. My point is Brake Hard early and instead of trailing off them you have the chance to stay on them as much as possible to make the corner. When doing an our braking pass the idea is not to carry speed througth the corner, but simply to make the corner. Thus you can carry the hard straight line brake a little deeper that you competitor (after starting a 1/2 car length deeper) and still make it around the corner. Sure it is slower, but the other guy can't get around so you win the battle.

If you wait till the end to brake you have no "extra" resevere braking to try an outbrake manuver. You simply fly off track.

M758

Not true at all. The brakes need to be release at the right time for that corner. That can be well after turn in depending on the type of corner. If you have stopped braking by turn in you will be giving up tons of speed to those still braking after turn in.

This to me is the heat of trail braking and no it is not a Novice technique.

APKhaos

That's my technique too. My second ever instructor used it, and I never forgot it. For some students, a graph drawn in space works well too. I call it a braking profile, but the essence is a simple pedal pressure vs time curve to illustrate the 'back loaded' vs 'front loaded' brake technique. It also help to illustrate the difference between an initial stamp on the brakes [badness] and a positive squeeze to get the weight transferred then a strong pressure to get the work done.

Its easy and dangerous to get early students bamboozled with any reference to trail braking. The nice thing about teaching the three stage 'squeeze to transfer weight, squeeze harder to get best braking effort, then smoothly release at your turn-in speed' is that it very soon results in the student being at turn-in speed a hundred feet or more before the turn-in. That's a good thing. I want them to repeat that a few times for a given corner, to convince themselves that it is consistent and repeatable. Then its time to shift the braking point half that distance closer to the turn. Repeat as required.

This works well for early stage students, and also gives more advanced students a systematic and repeatable method to use when learning new tracks. Its also an easy transition to teach trail braking when the time comes. After all, its just a matter of changing the release profile, right?

riverflyer

This has been a great thread. I don't live near a track and get limited track time so much of my driving "skills" are self taught. I read some things I have learned along the way here and also some ideas that were new or expanded to my knowledge.
thanks.
I would love to hear more about brake pads relative to your posts in this thread, ie pads for particular kinds of tracks, braking styles or car setups.
I like what Larry said above high first bite pads, would like to know what pads you favore and what others prefer as well.

Rob 97 993c2

i agree using 'squeeze your arm' as a technique. David Murry did this with me as well at the Glen when he was trying to get me to trail brake deeper into the turns (see thread from 2 weeks ago)
He goes a step further by varying his turn-in arc (e.g. tight turn to slow down, open wheel for faster) and braking all the way to the apex.