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Does it not depend on the balance of the car and grip level though? i.e.steering with the brake or using it to rotate the car. In some cars, you can trail brake to the apex and there is enough grip and balance to rotate the car off brakes. Others don't rotate as much off the brakes.
To a certain extent... The phenomena and technique is NOT platform dependent, however the amplitude and speed of control inputs may be.
I equate using the brakes to steer the car (reduced steering lock required for the given arc) with "brake turning" or the original definition of "trail-braking," using the brake release rate allied with steering input AGGRESSIVELY enough to pivot on the outside front to a controlled degree and GENERATE more slip angle in rear than in the front.
VERY few people do this to the degree necessary to truly describe what they're doing as "brake turning."
Whether it's dragging MORE pressure past a certain steering angle, in relation to the decay of speed, to get the car to "point" downstream SOONER, or "popping off" or sudden release to lift the rear to scootch it around, machts nichts, the rotation component HAS to be there.
VERY few achieve this. For rotation to occur, there HAS to be a measurable, controlled widening of the arc of the rear axle (in radius) OVER the arc of the front axle. The result is often seen in a marked reduction of steering angle input, hence steered angle of the vehicle. That is NOT to be confused with a "correction."
Some really fast people call that intersection of the generation of rotation, properly balanced and measured by MAINTAINING maximum gSum between the end of longitudinal braking and maximum cornering load, "coasting." I hate that word, so I just call it maximum utilization of the tire.
To do this, the car needs to work well and the driver needs to be able to finely tune the gradations of amplitude in steering and brakes, as well as TIME A DYNAMIC COMBINATION OF ALL THESE THINGS JUST RIGHT!
On any given weekend, I can count on my hands and toes those who ACTUALLY "brake-turn" their cars well...
At the Glen in Sprint Race 1 for Red, Cory was, John wasn't, in Turn 1. I watched every lap.
Cory slowed a touch more, brought ALL of these elements and ingredients toghether, and I could SEE the precise amount of yaw and where in the corner and in relation to the apex that occurred. He beat John off the approach to the apex and apex (and used less exit curbing while doing it), every lap. Textbook.
That is all.
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I think its actually much simpler.. you want to slow the car down straight for maximum braking effect, and then have residual brakes applied through and after turn in to not only help front wheel steering force (more weight transfer), but take advantage of additional braking distance available. (meaning you can brake later). i dont think of it as it being needed for car rotation..... that implies to mean that you are over slip angles and that usually means less speed and g forces at that point. at brake release, you require max g loading and longitudinal balance...... so brake application release and technique is key.
Whether it's dragging MORE pressure past a certain steering angle, in relation to the decay of speed, to get the car to "point" downstream SOONER, or "popping off" or sudden release to lift the rear to scootch it around, machts nichts, the rotation component HAS to be there.
VERY few achieve this. For rotation to occur, there HAS to be a measurable, controlled widening of the arc of the rear axle (in radius) OVER the arc of the front axle. The result is often seen in a marked reduction of steering angle input, hence steered angle of the vehicle. That is NOT to be confused with a "correction."
Some really fast people call that intersection of the generation of rotation, properly balanced and measured by MAINTAINING maximum gSum between the end of longitudinal braking and maximum cornering load, "coasting." I hate that word, so I just call it maximum utilization of the tire.
I think this is, in essence, what Dan Clarke taught me the very first time I worked with a professional coach.
Interestingly, his approach was to *pause* for 2-3/10ths of a second between the brake release and getting on the throttle because, as I understood it, the rotation is quicker due to the reduction of friction absent brake or throttle input.
It's remarkable to feel/observe the difference in how I can take the same turn, and can either optimize momentum and receive the gift of rotation by just being patient before trailing on the throttle!
OR can clunkily crunch through steering inputs and brake/gas dynamics to wrestle into a forced rotation
Interestingly, his approach was to *pause* for 2-3/10ths of a second between the brake release and getting on the throttle because, as I understood it, the rotation is quicker due to the reduction of friction absent brake or throttle input.
Hmm, now where have I heard this before?
I think part of it is just a bit more adhesion for the front tires to pull the nose of the car around as well as keeping the car more settled. 0.2-0.3s sounds about right -- it is a very slight pause.
I think this is, in essence, what Dan Clarke taught me the very first time I worked with a professional coach.
Interestingly, his approach was to *pause* for 2-3/10ths of a second between the brake release and getting on the throttle because, as I understood it, the rotation is quicker due to the reduction of friction absent brake or throttle input.
It's remarkable to feel/observe the difference in how I can take the same turn, and can either optimize momentum and receive the gift of rotation by just being patient before trailing on the throttle!
OR can clunkily crunch through steering inputs and brake/gas dynamics to wrestle into a forced rotation
Correct, for every tire contact patch except the outside front entering the corner.
On the latter, that's what most people do...
Originally Posted by TXE36
I think part of it is just a bit more adhesion for the front tires to pull the nose of the car around as well as keeping the car more settled.
-Mike
Every driver is in too much of a hurry... in all the places they need to wait...
And not in enough of a hurry in places where it helps tenfold to do so...
We probably need to separate the car balance part from the line optimization part as we are really talking about two different things.
From a physics perspective trail braking helps optimize our tire force direction for a faster line. This goal is the same for all cars, but most want the typical reduction in brakes with increase in steering. Dirt cars do it by driving sideways instead.
This really has nothing do with trying to drive on the outside of the traction circle, that's just driving at the limit which you should ideally be doing all the time anyway. You can drive perfectly around the outside of the traction circle and still be slow if you aren't on the right part of the circle in the right part of the corner. It also has nothing to do with transferring load to the front to help the front tires steer. Both front and rear tires are changing the car's trajectory.
When talking about trail braking most people seem like they are normally discussing the steering and brakes affect on entry balance. We ideally want to drive with front and rear tires perfectly at the limit as we do the braking and steering trade off. This will cause a steady decrease in slip ratio and increase in slip angle up to the apex which is what is often called rotation. All the little tips you hear like pausing, brake release speed, etc... are aimed at getting a car to either use less or more of the rear tires depending on what you need to keep the rear tires at the limit without going over. These are all very car/setup dependent though and are really just about learning to drive at the limit during entry.
From the driver's perspective I'd recommend not to focus on attempting to "manually" trail brake by trying to do a steady transfer of braking to steering. Most people that do this are not driving at the limit and hindering the progress. Instead try to focus on maintaining the limit during entry while driving fast enough during entry where you can't get on the throttle until the apex. Doing a more constant speed entry loses very little time to proper trailbraking and as your car control skills improve you can work on directing your tire forces a bit better to gain some time.
We probably need to separate the car balance part from the line optimization part as we are really talking about two different things.
From a physics perspective trail braking helps optimize our tire force direction for a faster line. This goal is the same for all cars, but most want the typical reduction in brakes with increase in steering. Dirt cars do it by driving sideways instead.
This really has nothing do with trying to drive on the outside of the traction circle, that's just driving at the limit which you should ideally be doing all the time anyway. You can drive perfectly around the outside of the traction circle and still be slow if you aren't on the right part of the circle in the right part of the corner. It also has nothing to do with transferring load to the front to help the front tires steer. Both front and rear tires are changing the car's trajectory.
When talking about trail braking most people seem like they are normally discussing the steering and brakes affect on entry balance. We ideally want to drive with front and rear tires perfectly at the limit as we do the braking and steering trade off. This will cause a steady decrease in slip ratio and increase in slip angle up to the apex which is what is often called rotation. All the little tips you hear like pausing, brake release speed, etc... are aimed at getting a car to either use less or more of the rear tires depending on what you need to keep the rear tires at the limit without going over. These are all very car/setup dependent though and are really just about learning to drive at the limit during entry.
From the driver's perspective I'd recommend not to focus on attempting to "manually" trail brake by trying to do a steady transfer of braking to steering. Most people that do this are not driving at the limit and hindering the progress. Instead try to focus on maintaining the limit during entry while driving fast enough during entry where you can't get on the throttle until the apex. Doing a more constant speed entry loses very little time to proper trailbraking and as your car control skills improve you can work on directing your tire forces a bit better to gain some time.
Adam - thanks for this reply.
I have a thought exercise with respect to braking which I cannot quite reconcile. Let me try to explain and ask that you help straighten out my thinking. Let's just say I have tires that have 1g available to me. I can brake at 1g and I can accelerate in straight line at about .4g. So in any corner I could brake at 1g to start with and the make the turn at .4 long G and .6 Lat G Or I could brake earlier and accelerate at .4 long G and turn with the remaining 0.6 g. Let's ignore sum of square roots for now. Why doesn't this work in real life? What am I fundamentally missing?
I have found that my quickest time through Turn 3 at TWS are when I brake earlier and am rolling into throttle prior to Apex-not100% mind you.
We probably need to separate the car balance part from the line optimization part as we are really talking about two different things.
From a physics perspective trail braking helps optimize our tire force direction for a faster line. This goal is the same for all cars, but most want the typical reduction in brakes with increase in steering.
This really has nothing do with trying to drive on the outside of the traction circle, that's just driving at the limit which you should ideally be doing all the time anyway.
You can drive perfectly around the outside of the traction circle and still be slow if you aren't on the right part of the circle in the right part of the corner. It also has nothing to do with transferring load to the front to help the front tires steer. Both front and rear tires are changing the car's trajectory.
When talking about trail braking most people seem like they are normally discussing the steering and brakes affect on entry balance. We ideally want to drive with front and rear tires perfectly at the limit as we do the braking and steering trade off. This will cause a steady decrease in slip ratio and increase in slip angle up to the apex which is what is often called rotation. All the little tips you hear like pausing, brake release speed, etc... are aimed at getting a car to either use less or more of the rear tires depending on what you need to keep the rear tires at the limit without going over. These are all very car/setup dependent though and are really just about learning to drive at the limit during entry.
From the driver's perspective I'd recommend not to focus on attempting to "manually" trail brake by trying to do a steady transfer of braking to steering. Most people that do this are not driving at the limit and hindering the progress. Instead try to focus on maintaining the limit during entry while driving fast enough during entry where you can't get on the throttle until the apex. Doing a more constant speed entry loses very little time to proper trailbraking and as your car control skills improve you can work on directing your tire forces a bit better to gain some time.
Not sure where to start individually, so I won't. Some of these conflicting statements are presented as if this is some kind of static exercise. It's not. It's a dynamic one...
The last, in bold, is not supported at all by experience and application, as supported by the data.
The data I have and have observed, from multi-championship winning drivers up to a WDC, IMSA and several FIA GT champions, does not support the above advice.
Even less so for the track day/club racer/enthusiast, one with LESS experience gauging the "limit," without going over it in an unrecoverable way.
Lastly, the idea of "stepped learning," or mastering one method of skill execution, only then to progress to another upon competence, is not the most efficient nor the most congruent educational approach.
Proceed with caution, as the corner entry phase is the one filled with most risk when trying to "judge" the "limit."
see my inserts below:::::::::::QUOTE=AdamBrouillard;14235555]We probably need to separate the car balance part from the line optimization part as we are really talking about two different things.
not really.. they are intimately interactive . all forces, speeds distances over time, add up!
From a physics perspective trail braking helps optimize our tire force direction for a faster line. This goal is the same for all cars, but most want the typical reduction in brakes with increase in steering. Dirt cars do it by driving sideways instead.
yes, true
This really has nothing do with trying to drive on the outside of the traction circle, that's just driving at the limit which you should ideally be doing all the time anyway. You can drive perfectly around the outside of the traction circle and still be slow if you aren't on the right part of the circle in the right part of the corner. It also has nothing to do with transferring load to the front to help the front tires steer. Both front and rear tires are changing the car's trajectory
you cant drive at the edge in all dimensions all the time. its force vectoring at its finest. i agree and disagree with the above. you are right, we dont focus on driving perfectly around the traction circle, because we are like a spacecraft going to the moon going into orbit. it has a LOT to do with transferring weight to the front to increase their force and start the turn, as well as slowing the car down, until such a point where the car is not slowing anymore and is just applying cornering forces.. the front tires and rear tires are applying forces with slightly different slip angles
When talking about trail braking most people seem like they are normally discussing the steering and brakes affect on entry balance. We ideally want to drive with front and rear tires perfectly at the limit as we do the braking and steering trade off. This will cause a steady decrease in slip ratio and increase in slip angle up to the apex which is what is often called rotation. All the little tips you hear like pausing, brake release speed, etc... are aimed at getting a car to either use less or more of the rear tires depending on what you need to keep the rear tires at the limit without going over. These are all very car/setup dependent though and are really just about learning to drive at the limit during entry.
From the driver's perspective I'd recommend not to focus on attempting to "manually" trail brake by trying to do a steady transfer of braking to steering. Most people that do this are not driving at the limit and hindering the progress. Instead try to focus on maintaining the limit during entry while driving fast enough during entry where you can't get on the throttle until the apex. Doing a more constant speed entry loses very little time to proper trailbraking and as your car control skills improve you can work on directing your tire forces a bit better to gain some time.[/QUOTE]
I agree here too, but slightly disagree with a more constant speed entry . i will always run up on a constant speed entry racer, due to the fact that im going faster and deceling longer. (and have more weight up front due to transfer and have more cornering forces available) however, in the learning stage , you are correct.
I have a thought exercise with respect to braking which I cannot quite reconcile. Let me try to explain and ask that you help straighten out my thinking. Let's just say I have tires that have 1g available to me. I can brake at 1g and I can accelerate in straight line at about .4g. So in any corner I could brake at 1g to start with and the make the turn at .4 long G and .6 Lat G Or I could brake earlier and accelerate at .4 long G and turn with the remaining 0.6 g. Let's ignore sum of square roots for now. Why doesn't this work in real life? What am I fundamentally missing?
I have found that my quickest time through Turn 3 at TWS are when I brake earlier and am rolling into throttle prior to Apex-not100% mind you.
Thanks in advance.
Denis
In a standard corner it's always better to err on the side of early acceleration from a laptime perspective. Rather than throttle application look at your speed. Even though you are rolling on throttle you might still be losing a few mph prior to apex. As far as lat vs long, remember the car is rotating as it goes through the corner, whichever combination gives you the highest acceleration in the direction of the straightaway is what you want. There are various clues you are on the right track mostly related to what you did with the throttle and steering. Hope this helps, let me know if it didn't answer your question though.
Last edited by AdamBrouillard; 06-06-2017 at 09:06 AM.
The last, in bold, is not supported at all by experience and application, as supported by the data.
The data I have and have observed, from multi-championship winning drivers up to a WDC, IMSA and several FIA GT champions, does not support the above advice.
Okay, well I'll put some numbers on it as "little time" is subjective depending on where you are at competition wise. Less than a 10th per corner usually. Primarily I am trying to say that it is faster to drive a constant speed entry at the limit rather than trailbraking at 90 percent.
06-05-2017, 03:24 PM
