Speed Trace Shape with Trailbraking
08-24-2018, 10:53 AM
#1
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Speed Trace Shape with Trailbraking
I've noticed the deeper I trail brake the less pointy my vMin speed trace is, more of a hockey stick. Think turn 1 at Summit. Good bad or a step toward the right shape which should be...?
08-24-2018, 11:31 AM
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That's it. I use hockey stick to describe the shape all the time. That change in slope is when you realize that you've slowed enough and start trailing out of the brake and roll speed in. Great job!
08-24-2018, 01:25 PM
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I’d want to see, dynamically linked, driver control inputs (specifically brake pressure and steering, or LatG for the latter) plus the be-all, end-all measure for gauging trail-braking efficacy, Comb G or gSum.
on a colored map...
08-24-2018, 01:39 PM
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I knew I'd seen the description hockey stick before but I couldn't remember if that was good or bad .
Some shapes in specific corners are necessarily not what we want, I couldn't remember about this one. Agree and understand that you can create ideal speed traces in ways that aren't necessarily reflecting ideal driving and that while it tells a lot a speed traces alone doesn't tell us everything.
Some shapes in specific corners are necessarily not what we want, I couldn't remember about this one. Agree and understand that you can create ideal speed traces in ways that aren't necessarily reflecting ideal driving and that while it tells a lot a speed traces alone doesn't tell us everything.
08-24-2018, 02:37 PM
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I’d want to validate that with a couple more KPI, before I would pronounce success...
I’d want to see, dynamically linked, driver control inputs (specifically brake pressure and steering, or LatG for the latter) plus the be-all, end-all measure for gauging trail-braking efficacy, Comb G or gSum.
on a colored map...
I’d want to see, dynamically linked, driver control inputs (specifically brake pressure and steering, or LatG for the latter) plus the be-all, end-all measure for gauging trail-braking efficacy, Comb G or gSum.
on a colored map...
08-24-2018, 05:11 PM
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The gSum has to be maintained within a VERY narrow range throughout the EoB braking transition and into the cornering loading.
I think one of the biggest “kids” track day and DE drivers make of themselves is believing that they actually are trail braking, when they’re not.
This is one reason why SBRS went from calling this skill execution trail braking to “brake turning.”
Good discussion, though.
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08-24-2018, 06:13 PM
#8
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So what should the overlap of long and lat G traces look like for someone trailbraking effectively? Or put another way, for someone who isn't kidding themselves but is actually trailbraking?
09-05-2018, 10:17 AM
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I imagine watching your G trace you'll see a nice arcing transition from peak longitudinal deceleration to peak lateral acceleration.
09-05-2018, 11:25 AM
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What is even rarer is LongG being equal or even near equal to max sustained LatG.
I’d much rather use gSum or CombG, which is more accurate, more telling and where the Apex Pro does so well. If there’s ONE tool that can test and validate real-time the best execution of the fundamental skill of trail-braking (or more correctly, brake-turning), it’s that one.
Few drivers trailbrake, even when they think they do. Even less so do so properly. This is why Grant Maiman, Eric Foss, Lee Carpentier, Ross Thompson, Thomas Morley, Tom Long, Mike Skeen and a few others are so much better than their clients.
That and consistency...
09-05-2018, 01:06 PM
#11
I would expect to find little or no dip between LongG and max LatG, but that is super rare.
What is even rarer is LongG being equal or even near equal to max sustained LatG.
I’d much rather use gSum or CombG, which is more accurate, more telling and where the Apex Pro does so well. If there’s ONE tool that can test and validate real-time the best execution of the fundamental skill of trail-braking (or more correctly, brake-turning), it’s that one.
Few drivers trailbrake, even when they think they do. Even less so do so properly. This is why Grant Maiman, Eric Foss, Lee Carpentier, Ross Thompson, Thomas Morley, Tom Long, Mike Skeen and a few others are so much better than their clients.
That and consistency...
In the end I think it boils down to training and practice. The more time you spend behind the wheel the more you are able to develop as a driver and learn, implement, practice, and refine techniques. Even so there is a point at which talent runs out and some people just have a higher talent threshold than others. I was at a private track day with an OEM and they brought Billy Johnson in to do the driving to benchmark a few vehicles. It was a jaw-dropping moment to watch him climb into a car he's never driven before and within 4 laps he was logging times 6 seconds faster than the OEM's performance engineers who'd spent the last 3 years developing the car.
09-05-2018, 01:25 PM
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In the end I think it boils down to training and practice. The more time you spend behind the wheel the more you are able to develop as a driver and learn, implement, practice, and refine techniques. Even so there is a point at which talent runs out and some people just have a higher talent threshold than others. I was at a private track day with an OEM and they brought Billy Johnson in to do the driving to benchmark a few vehicles. It was a jaw-dropping moment to watch him climb into a car he's never driven before and within 4 laps he was logging times 6 seconds faster than the OEM's performance engineers who'd spent the last 3 years developing the car.
In observing and evaluating tens of thousands of drivers over the last several decades, especially in a highly structured setting like Skip Barber Racing School, along with fellow instructors who have the same or greater level of experience, we find that in general, the level of “talent” displayed by a driver takes them only so far.
While there are certainly individuals who “get it” and “get it done” sooner than others, in the end it is enhancing the knowledge base, possessing unending motivation to get in absolutely every car, kart or vehicle they possibly can, and practicing perfectly that makes the end result difference.
There’s still a huge comfort and confidence gap between even “advanced” and “instructor level” skill execution in comparison to a good pro like Leh Keen, Billy Johnson and less so between those good pros and top level drivers like Jeroen, Joerg or Stefan.
The wider you cast the next, the broader your experience with what is possible. Cool stuff!
09-05-2018, 02:22 PM
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Can you explain why brake turning is a more precise or informative term than trail braking is? From context it appears to be intuitively obvious to you but it isn't at all obvious to me.
Thanks for the thoughts on what a trace will look like when trail braking.
Thanks for the thoughts on what a trace will look like when trail braking.
09-05-2018, 04:37 PM
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Basically, he outlined how the phenomena of using a proactive strategy of control-input-relationship-to-directing-weight-transfer, past the traditional end of "straight-line/threshold braking," could reliably, safely in EXTREMELY efficiently aid in shortening the "rotation" moment and point the car in a heading more advantageous to progress to WOT (wide open throttle).
At the time, Jim Russell and later Bertil Roos were the contemporaries in this new business model of professional racing schools, and there was (and still is) a debate over what should happen in the period between EoB (End of Braking) and the apex...
Skip, mostly through study of other SCCA National Champions (he won Formula Ford in 1970 and 1971), then later, F1 colleagues, top-level F5000 and Can-Am drivers, described how the end of the slowing moment (in physics) and the release of the brake, WITH lateral forces well in play, could influence the car rotating on the outside front tire to aid the driver in changing direction.
This visible yaw was what he saw as common to all the great drivers he observed, particularly at slower corner entry well past turn-in but before the apex was clipped. This was DIFFERENT than the approach and technique some of the other schools were teaching, and he seized upon using this term "trail-braking" as one of the key differentiators in his curriculum and his school.
Most drivers who are not familiar with or even actually develop enough rotation to reduce steering input, for any period of time other than a premature correction, THINK they are trail-braking, hence the "watering down" of this important concept.
The entry to VIR Hog Pen through Turn 16A is NOT "trail-braking," because you are not TRYING to influence the car's yaw (or heading) through pivoting the car on ONE of the four contact patches, but people THINK they're "trail-braking" because they have the wheel turned AND they are applying brake pressure. That is NOT what Skip's concept was describing. Whay Skip was talking about was what MANY drivers DO successfully at the entry of Turn 4A...
Drivers who are continuing to brake PAST the initiation of steering input, but NOT enough to proactively CHANGE and CONCENTRATE the weight on the outside front tire, are not, in the classical term, "trail-braking." They call what they are doing "trail-braking" because they are "trailing the brake" INTO the corner, but the phenomena of using this to govern the weight transfer to effect the yaw, the rotation, is not there. Super easy to see on the data.
In order to eliminate confusion (which may have INCREASED it, inadvertantly), the SBRS curriculum renamed this concept and it's execution about twelve or fifteen years ago to a more descriptive "brake-turning" terminology. Which IS more "correct" and which is why that term is more descriptive and accurate, at least to me working with this concept nearly every day.
The goal of true "trail-braking" or "brake-turning" is to influence and LESSEN the amount of steering lock required to negotiate these slower corners. That's the real crux...
A dip between CombG (or gSum, same thing), between max braking and max cornering is indicative of NOT USING enough of the tire's demonstrated grip PRECISELY at the point of MOST desirable yaw, or rotation. Problem is, most drivers are nowhere close to equal or even near equal in those measures between Longitudinal axis and Lateral axis. LongG is usually half to two-thirds what the LatG measure usually is, and Buddy Fey has proven it needs to be not more than 10% spread.
It's a great question and one that data has helped illuminate in ways no human instructor can easily quantify. It also allows incremental increases in "asking" the tire and the car to do something that is hard to get used to! Great stuff.
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