The End of Braking...
#46
Addict
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You are saying that Jeremy Dale is full of it then?
What about this text from "Going Faster":
You will find that, for the same corner, lower powered cars will have earlier throttle-application points than cars with more horsepower and greater acceleration potential.
Is that all wrong too?
I am not sure how motorcycles apply here, but I certainly trail braked later and got on the throttle later on my 1000cc 190 HP bike than I did on my 600cc 120 HP bike. I learned how that worked from an AMA Pro that rode both 600cc Supersport and 1000cc Superbike bikes.
Scott
What about this text from "Going Faster":
You will find that, for the same corner, lower powered cars will have earlier throttle-application points than cars with more horsepower and greater acceleration potential.
Is that all wrong too?
I am not sure how motorcycles apply here, but I certainly trail braked later and got on the throttle later on my 1000cc 190 HP bike than I did on my 600cc 120 HP bike. I learned how that worked from an AMA Pro that rode both 600cc Supersport and 1000cc Superbike bikes.
Scott
#47
I'm in....
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Hmm, don't think so. I think the ability to get into the throttle has to do with grip and balance and the question of whether or not you're going to upset the car in terms of grip and direction. If you're at the limit of grip mid-arc and are coasting or maintaining throttle, it doesn't matter what degree of 'acceleration potential' you have. Perhaps torque, LSD, and right foot feel are a factor about how you feed the throttle in
#48
Nordschleife Master
The biggest difference, IMO, switching between slower cars and faster cars (I drove in a Spec E30 in last years 25 Hours of Thunderhill) is with the slower cars you *must* carry more speed in on entry and quite frankly, the application of throttle in the middle to exit means little (because the power output is so small and it's effect on the car is so little). It's why I don't believe a Spec Miata or a Spec E30 is the "perfect" car to learn in (albeit, very good). You won't learn all the skills/technique you'll need to survive in a faster car. You'll have to move to a faster car to learn them.
-mike
#49
Race Car
Based on what I am reading here, what is written in chapter 5 of "Going Faster" regarding trail braking and throttle application is incorrect and should be disregarded.
Scott
#50
Rennlist Member
Sure! I try as much as possible to have enough entry speed that I need to keep slowing the car down until the apex, but if I don't get it rite or the corner has a "long middle" then there's definitely some coasting. In the Porsche I feel that going to the throttle a little too early (to makeup for over slowing) almost always results in an exit understeer which hurts more than coasting for just a moment to let the car get pointed. It's actually been one of the hardest things for me to do... my natural instinct is to just go to the throttle (even a little bit) instead of coasting, but many times it makes the problem worse.
Looking at my own data, I can always tell if I'm not carrying enough speed on entry because I'll get 10-25% throttle at or before the apex to makeup for the over slowing. The faster I'm getting, the more I'm coasting. :-)
-mike
Looking at my own data, I can always tell if I'm not carrying enough speed on entry because I'll get 10-25% throttle at or before the apex to makeup for the over slowing. The faster I'm getting, the more I'm coasting. :-)
-mike
And key to the discussion about braking, look at the G-Sum (which is a dangerous topic on RL...) and compare it with throttle and brake traces. Once the throttle is closed you are immediately hard on the brakes, there's no messing around with the initial application of the binders, tapering off to the apex. What does that initial application look like as a total percentage of brake pressure? it would be interesting to plot the apex vertically, it looks to be about two segments over from the yellow line.
There are so many erroneous techniques and concepts that get tossed around that it makes finding a real kernel a rarity. End of braking and throttle at the apex are two important ones.
#51
Rennlist Member
This brings us to a very interestiing yet little-discussed point: namelyy, that many of the very fastest & smoothest drivers will carry so much entry speed at the point that they are fully off the brakes, that they need to sort of "float" or coast the car briefly before applying throttle. If they went to throttle immediately, they would likely leave the track, because the chassis hadn't yet fully settled with the high entry speeds. Instead, it is faster (and safer) to be neither on the gas nor on the brake for a small interval of time in the corner, and THEN go to the throttle...
#52
Nordschleife Master
Problem is, you've got to have lots and lots of experience to make up your own mind, and to differentiate between what works and what doesn't.
Thank God, the journey's the fun part.
#53
Rennlist Member
This brings us to a very interestiing yet little-discussed point: namelyy, that many of the very fastest & smoothest drivers will carry so much entry speed at the point that they are fully off the brakes, that they need to sort of "float" or coast the car briefly before applying throttle. If they went to throttle immediately, they would likely leave the track, because the chassis hadn't yet fully settled with the high entry speeds. Instead, it is faster (and safer) to be neither on the gas nor on the brake for a small interval of time in the corner, and THEN go to the throttle...
#54
Rennlist Member
Great thread. Lots of good insight here. Thank you Ross for starting the discussion.
#55
Rennlist Member
I've had a conversation with some students that we shouldn't refer to that portion of the track as "the brake zone". Sure it's that, but those students focus on BRAKE NOW! and stare at the numbers. I want them to consider it the "get ready to turn" zone, and better develop the skill to look up and slow down just enough to make a good fast apex. I think it helps them to connect each component of a turn. And perhaps it takes a student's primary attention off the middle pedal so he can instead focus on where his eyes are looking.
#56
Rennlist Member
This is a good discussion. I've done what Mike suggested, and plotted my total Gs in this screen shot. This is T1 at Lime Rock a few days ago.
Top graph is throttle position; 2nd graph is brake pressure; middle graph is steering angle; below that is the combined G vector; and the bottom is the time gap between laps.
Two things this thread will encourage me to do: pay more attention to the end point of braking, and not the beginning, which you can see on my brake pressure graph; and try to get that dip in the combined Gs between 600 and 800 feet up!
Top graph is throttle position; 2nd graph is brake pressure; middle graph is steering angle; below that is the combined G vector; and the bottom is the time gap between laps.
Two things this thread will encourage me to do: pay more attention to the end point of braking, and not the beginning, which you can see on my brake pressure graph; and try to get that dip in the combined Gs between 600 and 800 feet up!
#57
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Van - Your's looks better than mine! I've been working on this idea of smoother transistion off the brakes for a while, but Ross's idea of picking an off brake point is a great way to think about it. I can't wait to apply it at my next event and at LRP in Big Bend in September!
#58
Three Wheelin'
Great thread all!
That would be interesting. The Pros I have right seated with (in same or similar cars as mine) essentially threw me up out of the seat on initial brake application and chirped the tires (yes with abs) .. Yet the car was not 'surprised' or out of balance at all (ie no wag, or side to side motion).
In talking to them afterward all essentially stated that the brakes were 'squeezed' on, so as not to unbalance the car, but done very quickly, and that the squeeze was to threshold, ie lock up, with immediate slight release. From that point, the brakes were released steadily so as to move weight off of the front tires and 'level' the chassis to prepare for turn in.. The end release is timed to be at the desired turn in speed with all four tire patches engaged with 'weight' moving fore to aft approaching apex, at a location that would change depending on the corner, speed, grip, etc.. If done right there would be a pause before one could again 'get on' throttle as essentially the car/tires would be at the limits (friction circle wise) and any additional input would unbalance the suspension/tire patches, and cost grip...
With new students I try to plant a seed re the above by teaching 'cadence braking' of sorts (usually after I show them in a ride). On the right type of corner, I try to have them apply their brakes on a cadence of '1,2,3'; hold, then try to have them release their brakes on a cadence of '1,2,3,4,5'.. for example (depending on corner). Sort of a simplified version of what I've been taught.. Seems to work in that it gets the student to think of engaging and releasing the pedal over time, and in differing manners, and not to 'pop off of it' at the end of the braking point. It also teaches the base technique for trailbraking (altho I do not necessarily tell them that)..
And key to the discussion about braking, look at the G-Sum (which is a dangerous topic on RL...) and compare it with throttle and brake traces. Once the throttle is closed you are immediately hard on the brakes, there's no messing around with the initial application of the binders, tapering off to the apex. What does that initial application look like as a total percentage of brake pressure? it would be interesting to plot the apex vertically, it looks to be about two segments over from the yellow line.
In talking to them afterward all essentially stated that the brakes were 'squeezed' on, so as not to unbalance the car, but done very quickly, and that the squeeze was to threshold, ie lock up, with immediate slight release. From that point, the brakes were released steadily so as to move weight off of the front tires and 'level' the chassis to prepare for turn in.. The end release is timed to be at the desired turn in speed with all four tire patches engaged with 'weight' moving fore to aft approaching apex, at a location that would change depending on the corner, speed, grip, etc.. If done right there would be a pause before one could again 'get on' throttle as essentially the car/tires would be at the limits (friction circle wise) and any additional input would unbalance the suspension/tire patches, and cost grip...
With new students I try to plant a seed re the above by teaching 'cadence braking' of sorts (usually after I show them in a ride). On the right type of corner, I try to have them apply their brakes on a cadence of '1,2,3'; hold, then try to have them release their brakes on a cadence of '1,2,3,4,5'.. for example (depending on corner). Sort of a simplified version of what I've been taught.. Seems to work in that it gets the student to think of engaging and releasing the pedal over time, and in differing manners, and not to 'pop off of it' at the end of the braking point. It also teaches the base technique for trailbraking (altho I do not necessarily tell them that)..
#59
Rennlist Member
VR - Can you elaborate on what you mean here in the context of bending the car into a turn?
This brings us to a very interestiing yet little-discussed point: namelyy, that many of the very fastest & smoothest drivers will carry so much entry speed at the point that they are fully off the brakes, that they need to sort of "float" or coast the car briefly before applying throttle. If they went to throttle immediately, they would likely leave the track, because the chassis hadn't yet fully settled with the high entry speeds. Instead, it is faster (and safer) to be neither on the gas nor on the brake for a small interval of time in the corner, and THEN go to the throttle...
#60
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THIS is why the CombG is SO valuable as a tool for measuring and evaluating this most critical phase.
My definition of "bending the car into a turn" is the successful blending of the release of the brake and the addition of steering input very close to the same rate (and near to the total tractive capability) as the tire can accept, throughout the entire transition.
Pros do this really, really well.
It encompasses reading your "butt gyro" to gauge the heading, therate of yaw development, managing the speed and the proper evaluation of the weight of the wheel to help determine where the tire is in acceptance of and at a high percentage of total grip used EVERY FOOT OF THE TRANSITION between big braking and big cornering.
Sorry, I just get excited talking about this...
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-Peter Krause
www.peterkrause.net
www.gofasternow.com
"Combining the Art and Science of Driving Fast!"
Specializing in Professional, Private Driver Performance Evaluation and Optimization
Consultation Available Remotely and at VIRginia International Raceway
Last edited by ProCoach; 08-14-2012 at 09:42 PM.