ColorChange

Mitch: Thanks, but I will soften or even correct what I say now if someone can present a good (sound) argument). Maybe I will soften with experience, or maybe I'll get even worse as my skills improve, my knowledge improves, and I have P car data to prove what I say.

Mark in Baltimore, are you insinuating that physics are dependent upon experience?

Bob Rouleau

mds - I agree with you. In case I have mislead you, please note that everything I have ever posted on TB is referenced to a 911. Driving a 944/51/68 my pals trail brake more than their 911 counterparts. I have observed good 360 Challenger drivers using trail braking when I dare not. The car configuration and type do affect how often you will use trail braking. CC may notice a difference between his mid engine Countach and his 996 TT in this regard. Having never driver a Countach, I cannot say for sure. Last season I was riding in a GT3 Cup car driven by a LeMans winner. He up-shifted while tracking out of a 100 MPH plus corner. I thought we were going to die. The car did absolutely nothing (to my surprise and relief). Had I done the same thing in my GT2 there would have been casualties. Car set-up also counts.

Mitch- on another thread long ago I attempted to define trail braking as continuing to break after turn in. I also said that TB is not turning in just as you fade off the brakes as this is the correct way to enter almost every turn by taking advantage of the larger front conact patch while trying to control weight transfer to the rear of the car.

Best,

Adam Richman

If you are saying that you are turning in while braking and not rotating the car, all this talk about friction circles is irrelevant - the car is nowhere near the edge of adhesion. Trail braking, while it may very well be in a text book as being on brakes while turning, is a means to change the orientation during the corner be it at entry, mid-corner or corner exit. Trailing throttle lift, trail braking both describe changing the orientation of the car with the pedals otherwise, you are just describing my mom driving to the store in her MR2.

IMO, braking down to the apex as a means to stretch out a straight is quite the slow way around the track. To do so, you have to leak to the apex and with that, entry, mid and exit corner speed all suffer to lenghten the previous straight - not efficient unless the car or driver have no means to do otherwise.

Bob Rouleau

Adam,

While I am not *the* proponent of trail braking since I drive a 911 and do indeed use it to compensate for understeer (i.e. rotate the car) I have used it under other circumstances - for example a decreasing radius turn at the end of a straight. The entry is relatively gentle and then it tightens up. The quick was was to brake while turning since the entry was fairly gentle -
and I could brake a fair ways into the corner.

My point is that there are few absolutes in the game we're talking about. To say "always trail brake or never trail brake" is almost guaranteed to be wrong.

Regards,

RedlineMan

Hey Guys;

Heck... I wasn't trashing Color. I admire his sticktoitiveness, if not his methodology. Oh... I don't know what the Hell he is saying half the time, but I at least applaud him opening his mind up a bit!

I don't trash people, so no one necessarily knows my intent, I suppose. When I do... trust me, YOU WILL KNOW. I just was searching for an analogy that might click, and discovered that what was developing was also a masterful punfest in the making. Could you all have resisted?

Adam - I'm right with you, and that is why I brought up a definition. ALL braking done after turn in is not TB in my book. TB is indeed to me some attempt to change the direction of the car for the better by means of brake induced rotation.

There is also Balance Braking occurring after turn in, which seeks to mitigate the skatey period when one is transitioning from brake (heavy front g-load) to cornering (heavy side g-load). I do not consider this TB. I wanted to differentiate this. I do FAR more of the latter than the former. In fact, the only time I TB to my definition is when I overcook my entrance!

Color, we just gotta trade rides somewhere. That is the only way for each to see what each is trying to say. You will and do smoke by gray matter with your models, but if you can critique your own driving as well as you hypothesize, you might just do OK!

The closest I will be to you is Mid Ohio, May 21-23. Other than that, BeaveRun October 2-3 doesn't really get that close. Think you can handle my raging 147HP?

Adam Richman

Bob, I don't believe I am saying to or not to trail brake - I am distinguishing braking while turning from using the brakes to turn the car. I am also suggesting that if you are going slow enough to brake all the way to the apex and not change the orientation of the car, there is probably a quicker way. All these discussions keep revolving around friction circles and g sum analysis and whatnot - to suggest that a car is maximizing its grip and braking and turning and the braking isn't augmenting the turning - I think its very misleading.

But John's comments make me wonder if some of this perspective (on terms) is based on the cars we drive (i.e. the power of the cars we drive). All cars are momentum cars - from 500 hp GT cars to my little 117 hp tot to a 91 hp ITC car - its just that in a lower hp car, you run out of alternative ways to go faster sooner and maybe we guys with the wimpier loud pedals have a different way of seeing it (maximizing our way around the track). Not right, not wrong, just different perspective. I know that I want to be on throttle as soon as possible for a turn (and where this is changes from turn to turn of-course), be it in my race car or in my S - I don't drive them any differently (well, I can listen to CDs in the 944 and the line is a little different but not too much) but I realize that in the grand scheme of things, neither car shows up on the hp radar.

FormulaOne10

Just to clarify from my perspective...

Mark Donohue, one of the guys that basically invented/discovered trail braking defined trail braking as braking to remain on the edges of the friction circle while entering a turn. This could mean:

A) You don't trail brake at all because doing so would actually give you less overall accel and therefore cornering force. This is would be identical to the acceptions listed by people so far. Additionally, it may not always be possible due to the configuration of a car.

B) You perfectly (well if you are Schumacher) trade off traction between braking and cornering and stay on the edge of the friction circle (whatever shape it is). This would be the ideal corner that Color is talking about.

C) You slightly trail brake because the geometry of the corner may change or going too deeply so will affect overall acceleration in a linked series of turns. For example you might be faster in the first turn with trail braking but you will be 5 mph slower on the final turn leading to the main straight. Now you loose that extra 5mph on the velocity integral (aka distance traveled) down the entire straight.

In all of the above cases, you are maximizing your potential overall G sum. Notice that to maximize the overall integral of g-sum you would have to trail brake whenever possible, even though it is not always possible.

ColorChange

John:

Not only will I critique my own driving, I will present any data someone wants to see (because I have a DAS). I have said many times before, I'm not very good, but I'm learning quickly. I am able to learn so quickly because I have a strong technical understanding (no where near complete), and I use a DAS for full analysis of my performance. This is the most efficient method for me.

Now I think you guys are offering to trade rides so you can flog my tt.

There is also Balance Braking occurring after turn in, which seeks to mitigate the skatey period when one is transitioning from brake (heavy front g-load) to cornering (heavy side g-load). I do not consider this TB.

John, I think this is exactly the trail braking I am talking about (and used by most texts). TB will do exactly what you say, offer a smooth (though very forceful) transition from braking g’s to turning g’s in most turns.

Adam, OK, I didn’t understand your point until the second explanation but now I think I do now. The braking and turning at the limit (on the fc) does induce some slip (4 wheel drift at the optimum slip angles for all four tires – in total, not individually), but there is no true significant additional yaw the braking normally involves as that would be past the maximum grip (and g’s) of the car. The way to think about this is at the limit on a skid pad, there is a lot of slip but not a lot of yaw difference between the front and the rear tires. The same thing happens at the limit while threshold braking, big slip, but no big yaw difference so the back end shouldn’t be coming around. This is a nice technique in certain race situations, but it is not that fastest and therefore not normally desired.

Formula: agreed.

SundayDriver

Color

There is some phrasing that is confusing me. The textbook trail braking is a rolling off of brakes as you start the turn so that you remain at the edge of the FC. Now this is a very short period until the car takes the set and is generating max lateral g's. This should be less than 10% of the corner for most cars (A big soft sedan may take more, a purpose built race car less).

Then there is what I would call "Heavy Trail Braking" a phrase I think you are also using. To me, this is pretty hard braking, usually all the way to the apex, or close to it. This gives you substantial extra slowing and rotation.

My sense of what you are saying is that you advicate heavy trail braking in most corners and most cars. Your turn by turn at Gingerman advocates huge tb, but never mild tb.

How does this fit with your theory and what you are describing?

ColorChange

Mark:

We are in agreement on the definition of trial braking. Oddly, it takes most cars a few tenths of a second at least to reach max lat g's. Faster than this (at normal speeds) induces suspension upset and you are no longer "smooth". So, what I am calling heavy trial braking is trading – long g’s and building lat g’s over about a second. I call light or normal trail braking 0.2-0.5 seconds. These are numbers of off my Countach. They will be different for different cars as you point out.

A typical 90 after a straight might take 3 seconds to complete. If about 1 second is taken up by trail braking, this is well more than 10%. If you want, I can post a graph of the data from my car. I do agree different cars will have different time bases, F1 being extremely fast.

I wouldn’t want to generalize and say I advocate heavy trail braking, but for 90’s at the end of straights and feeding other straights, definitely. The one turn at Gingerman I listed as just tb was what you would call mild tb. The others are what I am calling heavy tb.

Mike in Chi

Change

I'm no engineer. (Actually just an English Major)

But I have been impressed with the emphasis that has been placed on precise definition in this thread.

Given that I'd like to question a statement you made:

"I have only been on two tracks, Gingerman hot and Road America but only rudimentary work up there."

As I recall from another thread, you said you had only done track touring at Road America, and never driven it at speed.

I think in theory, and in practice, both "work" and "rudimentary" as an adjective would be misleading and an incorrect statement of your experience.

Unless "rudimentary work" has a different definition in engineering than in conversational English?

Suggestion: "I have x number of days at Gingerman and have driven Road America at 60 mph." would better convey your experience.

Tim Comeau

Ok, That's it! I'm taking my left foot braking thread and going home!..........................................................Just kidding. But I still do have to talk about threshold LFB and why and when I use it.

ColorChange

Mike, yes, you are correct. I have not driven much of RA at race speeds. They have open touring times during various races there and that is all I have done. You might get 2 or 3 turns at speed per lap as you work around traffic, but I never got much over 100 mph.

What do I call rudimentary work, basic video and data collection, and a few turns approaching race speeds. You seam to be implying that I purposely mislead people. I don't think I did. According to Webster's - rudimentary – elementary, incompletely or imperfectly developed. Did I mislead, especially when taken in direct contrast to Gingerman where I say I was running hot (fast)? I would call race work up determining lines, determining corner entry speeds, brake points, …. I am no where near that at RA and never said I was.

If you insist, I have 3 full days at Gingerman, 2 short partial days, and have driven RA at 100mph top speed but no where near racing speeds or racing laps. OK?

Mike in Chi

You might look up "work" too. Perhaps "research" would have served you better.

I guess it was your "110 mph through the carroussel" statement that you made a few weeks ago. I asked you in what car you did that, and your answer was in your countach. In a subsequent thread, you corrected that saying the DAS says that's what it can do in theory.

This is not meant to start a flame war.

I'm all for you sharing theory with us. There is something we can learn from everyone, no matter what his experience level.

My concern is that when a noobie with little or no track experience reads a post stated in such a knowing manner, that person may go out and try it. Be it trail braking, left foot braking or speeds for a given corner.

Nobody in a street car should be trying to do 110 through the carroussel.

Will you be doing the Road America DE this May?

I'd be glad to further discuss theory and actual experience with you. I'll even pay for the beer at Siebkens.

Here's the first one

Mark in Baltimore

Touring laps? Touring laps?! CC, your experience level seems to be dropping by the week.

Next week you'll be telling us your three full days at Gingerman were on your Big Wheel.

Kewl.

Seriously, your theories are really quite interesting and, when I read your posts, I hope to learn something, but the fact that you have so little real world experience is a tad troubling and, dare I say it, opens up a credibility issue. I would much rather take advice from an experienced, winning racer who has never used data acquisition than from someone who writes authoritatively, and intelligently, I might add, albeit with huge gaps in skill. Yes, I know I have the option of not reading the posts and this is what I have recently done, but like a radio that's turned on but not tuned to a station, there's still static.

As Mike said, many people will read your words and take it as gospel. Why not get more high speed lapping days under your belt so that you can meld your theories with your newfound experience? I, too, want the surgeon who's going to perform open heart surgery on me to have some experience beyond what was learned in text books.

In answer to your previous question, no, physics is not dependent upon experience but running a physics experiment well can be aided by experience. As previously posted, there are a whole host of other factors that determine the fastest lap time other than a paper theory.

In order to prevent accidentally misleading people, maybe you should preface your posts and findings with a disclosure that your experience level is minimal.

<edit> In another thread you posted this: "but seat time is definitely NOT the only way to go faster."

I find this downplaying of seat time to be disconcerting. So, without seat time, how do you propose to test and refine your theories? Based upon your heavy reliance on your models, I would expect that you would be able to turn some of the fastest laps your track has ever seen. Now, if you can't turn some blazingly fast times, you have to ask yourself, why not? IMHO, the answer is lack of seat time since your theories are not making you faster.

However, and I'm not being sarcastic here, maybe you have the skills of the next Jim Clark. Hell, he was a sheep farmer before he started racing. In that case, your skills have come preset and intact, needing only a theoretical understanding to refine your inherent speed.