P.Po

I wonder if it would be possible to use a DAS and a very good experienced driver to actually test exactly what mitch236 has asked? Real world tests would give us an idea, but with so many other variables (i.e. car setup, grip, temperature) we know the real world test would be inconclusive as to which is faster. So talking about it thereotically, which approach would be faster, is a very difficult question to answer.

My experience with TB has two stories.

At Mosport, in a basically a street 951 (with the Redline Rollbar of course!), I was trying to learn trail braking going into 3 and 9. I learned quickly 3 is not the place to be doing that!! Sjanes has passed while I am sitting stopped on the track after a spin. I spun beacsue I was learning to trail brake and messed up. 3 is probably to fast to trail brake anyhow. I also spun in the rain at nine... and that was because of an inappropriate application of TB. TB in the rain is REALLY hard in my opinion.

The other point I want to make is TB and Ice Racing. Funny thing is that trail braking will be used depending on the condition of the corner. The surface changes for every race and every lap, you sometimes don't even have a choice to trail brake and you have to be adaptive with it. If you are entering a corner, the changing grip sometimes forces you to be on the brakes while trying to get in position to not get passed or passed or even simply make the corner. So the decision wheather to trail brake or not, or what is faster boils done to whatever is happening at the point in the race. If you are used to always TB or not always TB, you will hit a snowbank and be out of contention very quickly. I wonder how this applies to track racing. I am sure it is very similar in racing conditions.

YMMV,
Patrick

M758

To me yes... That is straight line braking as taught in DE land.

Instructor to Student:
"Finish all your braking in a straight line. Then initiate turn in."

P.Po

sjanes wrote:
>So, does anyone get fully off of the brakes and onto the throttle (either accelerating or neutral throttle) before a corner?

That is exactly what I do for Corner 2 at Mosport. I found it faster and mroe comfortable to be on the gas when cresting and starting to dial in steering. But for almost every other corner that I drive, there is some mix of brake and turn in.... just not a lot.

-Patrick

JCP911S

Mitch,

One clarification on the above... every turn is different (DOH!). On a really fast sweeper, you may go from brake to max Lat Gs in the first third of the entrance, and be flat on the gas well before the apex. On a tight hairpin you will probably be braking almost up to the apex, and not on the gas until halfway thorugh the exit... the concept is the same, but the geometry of every turn is unique.

PT

Just curious - are you really completely off the brake, on gas before you initiate ANY turn in @ corner 2? While I'm definitely on gas before cresting the hill, I have already started the turn in very progressively and it "coincide" with my final release of the brake.

JCP911S

Trail braking (as I define it) has two benefits. The first is to extend the brake zone and allow later brake points. As described above, at turn in, you are not using 100 of the tire for cornering, so use it for braking or it goes to waste.

The other is to balance the car.

When you brake, the weight shifts forward and compresses both front springs. As you turn, weight shifts sideways and compteses the outside springs. As the springs compress, the car is in an unstable "transient" state as the load on the tire builds. Once the spring is fully compressed, the load on the tire is stable, and you can hold it at max Gs safely.

You cannot get the tires to Max G while in a transient, so this is in effect, dead time spent below 100% of the car's capability. This is the main reason racecars has stiff springs... to minimize transient time (the other is to minimize camber change, rideheight for aero, and other stuff).

When you brake, you compress the outside front spring. When you turn in you also compress the outside front spring. If you lt off the brake before you turn in, the outside front spring releases and has to be compressed again as you steer. By staying on the brakes as you turn in, you hold the spring in compression as you steer. As the cornering builds, you ease up on the brake, and if done right, the spring remains fully compressed and stable throught the whole sequence.

This is why people say they "drag" the brake to smooth out the turn in, or "set the nose". On fast sweepers folks occasionally use just a touch of left foot brake to compress the suspension right before they turn in so they can turn in faster... this is not done to slow down at all simply to shift the weight of the car.

"like everything else about driving there are no absolutes. Brake in a straight line is for safety and simplicity of novice students, as you progress, you will start to add more advanced techniques.

sjanes

With a green student, I agree, but we are not teaching a green student what is fast, but what is safe and consistent. With an "advanced" student, a student that understands weight transfer and has smooth inputs (especially a smooth brake release), my region teaches brake release during turn-in.

mitch236

So the concensous seems to be, trail brake during the transition phase ("turn in") and fade off by the "mid corner" phase. That is what I do in almost every corner. In fact, I can't think of any corner that I finish braking before the turn in. Therefore, I don't understand the concept of trail braking all the way to the apex, given the example above. When I am following a heavy trail braker, I catch them mid corner.

sjanes

This may have a bit to do with car setup as well. For Mosport, I have my car setup to be neutral to very very slight oversteer for corner 8. I find that this leaves me with a bit of understeer as I crest the hump for 2, so I release the brakes during initial turn-in to help with that. Your 944T may not experience the same turn-in understeer at 2, and thus the different driving style. I have a couple of times draged my brake release a little too long at the top of 2 and got a little wiggle on turn-in. Not a good feeling

As for the spin at 3, I still have the video

P.Po

You know.... I bet you are right now that I think about it... I mean I probably am starting to turn either while I am lifting off the brakes or transitioning. I know that I over slow for two because I feel way more comfortable being on throttle for the whole turn, I would hate to crest while still transitioning. Also, I am very confident in one and carry a boat load of speed off of it so I do brake long and not as hard as I can before two. I find a hard brake before two can unsettle the car if you carry it to far, so I try to have my breaking finished way before I crest. But I bet I am turning slightly before throttle on.... Hmmmm.... good point! I am not saying this is the best way... it is just what I was doing in the past!!!

-Patrick

sjanes

I think the main thing to remember is the difference between theory and reality. While the theory that some amount of deceleration can be faded off all the way to the apex, in reality this takes way more skill/feel/smoothness/precision/etc than is usually present in the DE environment. In reality, for most (all?) DE drivers to carry decel that far into the corner, they have to overbrake before turn-in (hence, you catch them). In reality, DE drivers are not on the FC. If they were, they would be in F1 or somewhere similar. In reality we are just a bunch of guys (and gals) that get about 25-35 hours of track time a year (some more, some less) and know enough to muster a finely built car that we don't want to destroy around a cool race track for our own amusement.

Just my $0.02.

Bob Rouleau

I am with Larry H on the question, unless you define trail braking as easing off the brakes at turn in, I would not TB in the example given either.

If the exit of the turn was a short straight leading to another 90 degree turn then I would TB into the first one trying to maintain my high speed as long as possible. It works out to time and distance. If by TB I can stay at 150 MPH for one second longer and I lose 1 second at 70 MPH I win by being slower at the apex since I will have covered more ground in the same time. This is a case where being first on the gas is not as big an advantage. At tremblant turn 10 and 11 are a good example. 10 is a right hander at the end of the back straight which leads to a short straight (200 feet maybe) which leads to an off camber 90 degree left hander. Getting on the brakes later on the straight is a better strategy in this case.

Stacey, if you aren't easing off the brakes just as you inititiate turn-in you will be sent back for remedial training.

Sjanes will shortly be a newly minted Instructor for those who don't know him.

Regards,

joey bagadonuts

I couldn't help but notice that the front-engine, rwd guys (mitch236, P Po and M758) are still on the fence, here. That doesn't surprise me since, as sjanes mentioned, different cars will use trail braking differently.

With a 911, there is a night and day difference between entering a corner with your foot on the brakes or not. By shifting the weight forward, grip increases dramatically in a 911 and you can really dive into a corner with amazing pace. Try entering with your foot mashing the throttle and you'll shift weigt backwards, lose grip and probably scrub wide of your clipping point.

I think entry speed issues are more pronounced with 911's than a balanced, front-engine car like a 951, 944 or M3. Shifting weight forward will not have as big an impact on these cars since the fronts already carry the engine weight.

I've also been on the track many times with these cars and they do not brake as deep into the corner as a 911. At one of my last track events, even a 350Z pilot who followed me commented that there was "No way" he could brake into the turn as late as I was. I think John (Redline Man) may have suspected this all along and was hoping to hear something new, right?

mitch236

I wonder if fading off the brakes all the way to the apex really is faster? Let's say you had the skills to be on the brakes all the way to the apex while keeping the car at the absolute edge of adhesion, would that be faster than fading off the brakes after turn in and keeping neutral throttle all the way to the apex while keeping the car at the absolute edge of adhesion. I think theory would prove that neutral throttle allows for higher arc speed than does using some of the available adhesion for braking.

P.Po

Excellent point Bagadonuts! Totaly agree...

To me that just adds more proof that TBing is something that MAY be applied for SOME circumstances but there can never be an absolute for any car/track/condition.

-Patrick