MaxLTV

I sent a some laps for a review by a coach, and his main feedback was that I needed to trail brake all the way to apex in several corners where I got to throttle rather early. It made sense to me and connected well with what I've heard before, so I spent a day working on it. No matter what I tried I could not make it work for the corners in question - staying on the brake, even at 2-3 bar pressure (35-40 bar typical lock-up pressure) was way overslowing the car. Trying to up the entry speed enough to compensate for that did not work and only resulted in understeer or drifts, although in the process I managed to get comfortable with a tiny bit faster entry speed but not nearly enough to compensate.

I was trying to understand what's going wrong there, and then it dawned on me - my slowest point of the turn on my fast laps was at the apex or 1-2ft before, despite getting on the throttle way earlier. So I was decelerating all the way to the apex despite being on the throttle much earlier than that. All the turns in question were more than 120 degrees, wide hairpins or carousels, so they are very long and with high entry speeds, two being close to the top speed of my light and high-aero car (Radical SR3). So even just coasting from the entry to the apex would scrub over 30MPH, and even the tiniest trailing of the brake all the way to the apex would slow down the car so much that I do not see a possibility to increase the entry speed to compensate (I tried, and ended up understeering or drifting - the car just would not turn in). In high-speed turns, the car slows down noticeably even at 50% throttle due to aero drag and scrub. So in this case, could it be optimal to pick up the throttle earlier, as long as the apex is still the slowest point of the corner? Or should I try to magic out the entry speed and line combination that would allow me to carry some brake until the apex while still not overslowing the car?

Cadaver

I'll chime in but take it with a grain of salt. Its a concept I was introduced to last year at Road America during a race weekend. As a primer, reviewing data and comparing to a pro coach while looking at the speed, brake pressure, and steering angle traces was pivotal for me to understand. Mentally grasping it is one thing, but executing is another. I would say if you are over slowing a corner, try moving the brake point deeper. Its about keeping the area under the speed curve higher. Your braking on entry, but its less pressure.

Another technical aspect of driving that improved this aspect of my drive and made massive changes was left foot braking. Literally took me to another level of a drive. Not just performance, but feel of the car. We steer with two hands, why not steer with two feet. I started with the sim, then transitioned to the track. Im sure another will chime in with a more eloquent description, but consider the trail brake a steering mechanism in addition to the steering wheel. When you coast, less weight is on the front. When you trail brake, more weight is transferred to the front and increases front grip which in turn allows more rotation. Try to make as much use of the traction circle as possible. Something about the transition to left foot braking really clicked and allowed me to rotate the car more effectively and essentially made the turn more "efficient" by using the steering wheel, but also using the brakes. Again, if you are still over slowing, I would adjust your brake point slightly deeper. Think hard initial brake then trail off. Really examine the time at full brake pressure as well. Often I was braking hard, but holding that pressure too long. Sorry for the discombobulated explanation. Left foot braking helped me learn to really rotate the car once I found the right brake point for a specific turn. It also helped me find that pressure of brake release that rotated the car. That rotation allowed me to get to full throttle much sooner.

Veloce Raptor

Max: while I don't know the full context of your coach's comments, or why he was making that suggestion, I will say this. Often, advanced drivers can benefit from moving the brake zone deeper into the corner. Let's say a particular corner requires you to brake for a total of 250 feet. Let's say there's no way around that. If you could move that 250 foot brake zone so that it literally ends at the Apex instead of 10 feet before the Apex, you will have extended the previous straightaway. If these are long straight aways followed by very tight slow corners, much like we have at COTA, this can yield a major lap time advantage by allowing you more real estate at full throttle. Again, I am not sure if this is what your coach was saying, but if so I get it. Thus, instead of you starting going to the throttle well before the Apex, which suggests you may have over slowed for the corner, you pick up throttle at the apex as you release the brake. You have extended the previous straight by quite a few feet, are slowing to the same minimum speed in the corner, and are making your speed graph more a tight V: One where the amount of real estate you are at your minimum speed is minimized.

ProCoach

There could be (and are) books written on this very quandary.

A couple things come to mind. I think you’re looking at individual control inputs and the car’s response, with or without those inputs, as individual conditions and not as a whole system for optimally taking the corner.

The idea of coasting, without evidence of the tire being maximally used, is an anathema to going fast. My observation is that far too many drivers overestimate the amount of “rotation” they choreograph to help turn the car in slower corners, if they actually rotate at all. They are almost ALWAYS done braking EARLY!

But, your coach is dead on the money. The idea of early throttle (the dreaded “maintenance throttle”) is a fallacy, in most cases and especially in the corners you outline so clearly above.

If you’re back to throttle and the throttle speed (continuous, relatively quick and uninterrupted progression to WOT) is slow or stalled, you’re done slowing too early. People often have NO idea how much the application of steering slows the car, and some cars require up to fifty per cent throttle just to offset the slowing due to scrub (steering input, lateral loading and RESISTANCE to forward progress by the front tires).Remember, there is substantially diminished aero at speeds lower than 60-65 mph, too.

Bottom line is throttle application in slow (< 60-65 mph apex speed) corners SHOULD NOT begin until you can “see your way out” of the corner. Obviously, most of the fastest drivers are proactive enough to influence their trajectory from the apex area or a few car lengths before all the way out of the corner BY THE THROTTLE, but that takes a lot of practice and confidence to REALLY do that and not just think you are doing that.

I think you’ve asked a great question, but I’d encourage you to look more carefully at the total use of the tire (measured grip in all axis) using gSum to determine how efficient your slowing is, slow substantially your brake release rate (“leaving enough brake for the corner”) and get away from the idea you have to be at a particular, elevated speed at turn-in as opposed to focusing on the end in mind, the apex area.

That is the issue for most club level drivers in competition, DE or track days. Looking at all these individual control inputs and influences on the path of the car without focusing on how to blend them together, all the while really using all or near the capability of the car, without a lot of risk.

While I think spot analysis can boot strap you (as it has here), this is why my remote analyses tend to be eight to twenty pages long with screenshots validating and illustrating the foundation behind what we’re talking about here. It’s not simple, and it’s going to take a lot of practice for you to break this habit.

Good luck!

ProCoach

+1,000!

LuigiVampa

Firstly, did anyone else read this first sentence in an Italian accent like I did? LOL

I worked with Dylan Murry at WGI a while back. Interesting to be coached by someone who is the exact same age as my daughter but he had knowledge beyond his years. Really great kid and I enjoyed working with him.

He noticed that I was overslowing in certain corners, and as a results, back to throttle before the apex. His trick was to tell me not to go back to throttle before the apex and force me to wait. Jumping back on the throttle masks how much speed you could have really carried into the corner, so by waiting, it highlights the error.

The best example of overslowing was going into the bus stop. Many drivers get all their braking done on the straight, make the turn into the bus stop, and immediately go back to power. Now I get enough braking done in the straight to allow me to turn into the busstop where I brake just that little bit more to allow me to get to the left. Then its back to throttle. Previously, I was back to throttle before the first rumble.

Force yourself not to go back to throttle, regardless of your speed, until you are at an "appropriate" part of the turn to do so.

winders

Let’s not forget that is really hard to trail brake to the apex of a turn if you are taking too late of an apex. When you late apex a turn you get your braking done early and mostly before you turn in. You know, the classic line often taught in DE because it is the safest line.

Veloce Raptor

Excellent point

MaxLTV

Sorry for the confusion but I was talking about long but very fast corners, not slow ones - 85mph v-min and 95mph v-min respectively, kind of like 1/3 to 1/2 of a circle on a giant skidpad. My v-min is right at the apex in both cases but I need to get to throttle way earlier than apex still to not slow down too much. I’m losing speed even at 70% throttle going around those circles. I will do gsum analysis later to understand if there is more speed at turn in - great point, I should have thought of that. I think that will answer the question definitively.

But my quest to brake later already paid off - got my first ever pole in Radical Cup Canada series and third place finish today. Was fighting off a much more experienced racer all the way until the last lap, but then fumbled a shift and settled for third. Still smiling ear to ear and trembling a little from all the adrenaline. This sport is amazing.

ProCoach

35-40 bar braking for a fast (>85 mph) corner is way too much, then. Congrats on your moving forward.

Manifold

I think the short answer is that we should be decelerating to the apex, accelerating from the apex. This seems to follow from the physics, and it matches what pro drivers are doing.

Depending on the corner, the deceleration could involve trail braking to the apex, or trail braking followed by some coasting, or even some light throttle to the apex if speed is still being scrubbed with the light throttle.

The acceleration phase will, of course, always require application of throttle unless the corner has a steep downhill, but even then some throttle will typically be needed.

Execution of this stuff is harder than the theory, i.e. easier said than done. But it's good to know what we're aiming to do.

ProCoach

Yes. It matches what the "pro" drivers are doing because they've found that that is the most efficient way to conduct the car around the circuit and they spend the most time trying to execute this goal.

Here's where the sticky wicket of terminology comes in. Trail-braking is not brake-turning.

The former is when the brake application continues (sometimes well) past the initiation of significant steering input WITHOUT deliberately introducing yaw (or a heading change).

The latter is when the proactively and planned timing and rate of release of the brakes concentrates the tire loading on the outside front and the car pivots, geenerating a significantly greater slip angle for the rear axle than the front to aid in rotation. Basically, the use of the car's relatively sudden and planned change in heading to reduce required steering input and make the car do more of the work. This is where set up work pays dividends.

Coasting is only required when the maximum demonstrated, sustained amount of grip AND ROTATION is acheived between the end of slowing and the beginning of the acceleration phase. Rarely does this occur except at the top level of driving, no matter who's doing it. A momentary slip or slide ain't it...

The last of your descriptions is what I see most people doing. This usually squanders any entry speed advantage they've been able to work up to.

If there is an extended period of the last of your description, this results in the OP's original challenge being able to go faster. To be avoided...

I would modify this to eliminate the downhill conditional and add the "crest" that breaks trtaction on the drive wheels when the suspension unloads.

Absolutely! To form such a clear vision in your mind of where you want to be, where you want to be headed and what you're going to do when you get there is more than half the battle.

Great thread.

winders

What could I do better here?:

JTT

First, I agree, this is a great thread, thank you! Second, thank you for this explanation as it’s really got me thinking, as a rookie. Thanks Peter!

Does this always require some level of coasting as inferred in the quote being referenced? I would infer that it “could” include coasting, but not necessarily?

Is this adjusted by rate of brake release? Flattening or steepening the curve? as well as yaw or rotation rate?

I’ve experienced something with absolute beginners, who have been taught the “brake in a straight line” technique. Too low entry speed, then applying throttle way early (trying to gain speed) and continuing, or actually increasing steering input (scrubbing speed), which seems to reduce overall apex speed and induce understeer, all while only accomplishing punishing tires to no advantage...but they feel fast because the tires are slipping

ProCoach

Coasting, by the definition used when objectively measuring this phenomena, is throttle <particular point AND brake <particular point. Add steering input and the speed can drop more rapidly when coasting condition is true (both measures <particular point).

Problem is, if you can extract demonstrated grip in each axis (front/back or braking/acceleration and/or side loading or max cornering) and then there is much, if ANY period between braking and cornering where that measured total grip in all axis drops by more than 10-15%, you have, in fact, over slowed in the transition.

Even with advanced drivers and a few instructors, I see drops as great as forty percent and extending for hundreds of feet, a double whammy!

Now, if the drop between max decel and max cornering is less than fifteen or twenty per cent, and the brake release and brake pedal release is choreographed correctly, the car is on just enough unstable to be, that the driver can induce proactively an “unstuck” condition, where the slip angle is allowed to grow at a greater rate than at any other time. This allows the car to point further down the road and more towards the heading required to exit the corner with less steering input. Obviously, during this time, any further pedal input (or abrupt steering input) COULD overtax the tires. Hence “no pedal” or coasting period.

Most drivers are FAR from doing this, with few doing this well at slow corners and almost all not doing it at all in fast corners. But this IS the way top pros go faster.

Bottom line is your first question/supposition is correct.

So is your second.

The way to improve is a) reduce the percentage of demonstrated grip drop off BETWEEN the max decel and max cornering (even if decel negative g is not as much as max cornering g) to an acceptable level (one that allows the transition to occur at or close to the traction “limit “) and b) REDUCE the period (distance/time) that that drop covers.

It is VERY hard to get this JUST right. Really hard. But the drivers that have practiced car control exercises to they understand and can expect the car to behave a certain way when moving the weight distribution around with hands and more importantly, feet, and proactively DO that, are flat out faster.

The “tail,” or lengthening and flattening the brake pressure (amount) on release, AFTER doing what VR suggests, moving the whole braking zone INTO the corner entry phase, is how a lot of pros and talented ams do it.

When drivers simply try to shorten the braking period, the sphincter sensor naturally goes off the scale and the sudden brake release and excess speed at the turn in point naturally upsets the platform.

When they realize they have no gun at their head to get the same slowing done BY turn-in, but can extend release trading off braking grip for lateral grip in a smooth progression, but at a speed and tractive limit where the car is MORE responsive to the turning moment (yaw, rotation, whatever you want to call the phenomena of the car sliding more at the back than at the front so it needs LESS STEERING input), then they make the breakthrough most are looking for and achieve what nearly all top level drivers are doing on a regular basis.

It’s been a fascinating study over decades, enhanced with real numbers that show incontrovertibly where the driver is now and where they need to go. Also, what they’ve done when they have it just right!

I’ll add that in faster corners, the braking decel may be less, may be longer and acceleration MAY start slightly earlier than in slow ninety degree or tighter corners, but the same tenets apply. No or little drop in total (all-axis) grip (on a level or close to level surface) and if there is any before the apex, extend the brake zone closer. If the drop is at or after the apex, fix late throttle application to remedy the drop in total grip growing too quickly from the scrub.

It’s really cool to study this, and there are those of us who may never do it was well as we want to do it. That’s why we keep coming back!