uh...yeah...that's what I meant

and I was hoping to get home and correct my quote before anyone noticed...actually thanks for the actual quote because you saved me some time tonight. I think it's very appropriate to this discussion.

Thanks Brian

 

You should still look it up. I'm just paraphrasing from my memory as well. In fact, I can't find my Speed Secrets 2 book (I think it's in that one), so I'll have to trust your quote if you find it.

 

JC
If the driver overheated his tires, their grip would drop and therefore his g sum would drop.

JCP:
You are absolutely wrong. Please read the rest of my post.

M758:
Some DAS’s do incorporate GPS line analysis, but even then, the DAS won’t directly show you the best line. It is easiest determined by purposely driving different lines and seeing what is fastest.

Mitch236:
Generally agree with you. I set my DAS display to show digital speed. It works great!

BobDallas:
All the quotes Shown below say maximizing g’s is critical. What I think you are saying is that if you over brake for example, you will feel more g’s while braking (yes) but then you will be too slow and not feel as many g’s while turning. G maximization is absolutely the goal of the driver, just no unnecessary g creation.

Brian P, I agree completely. I have already ordered the speed secrets books as you guys seem to like them.

Here are some quotes that should help the rational.

Vic Elford "High-Performance Porsche Driving" book, talking specifically about a 911 car.

page 101-102 "Trail braking is the term applied to gently trailing off the brake as you increase steering into a corner. ... At the turn-in point for a corner, the steering effort required is perhaps 10 percent, which still leaves 90% of the tires’ ability available for braking. The deeper the car goes into the corner, the more steering is required and, thus, the less is available from the tires for braking, which is allowed to “trail off.” When you arrive at the “apex” of the corner you are using the steering to maximum and you have no braking ability left. All the way from the turn-in point to the “apex” you reduce the braking as you increase the steering.”


"Race Car Vehicle Dynamics” by William and Douglas Milliken.

Page 9 “ The problem imposed by racing may now be summarized as one of spending as much time as close as possible to the potential vehicle g-g boundary.

Page 345 ”It was concluded that race cars should have large “g-g” maneuvering diagrams throughout their performance envelope and that race drivers should operate close to the diagrams boundaries.


Carroll Smith, “Drive To Win”

p2-28. "for maximum performance we must "ride the rim" of the traction circle. "

P2-32 “The most important part of any corner is the slowest part – from turn-in to the point where making the chosen apex is a certainty. If the corner entrance is done properly – with maximum speed carried through each portion, the minimum elapsed time and optimum throttle on point - the exit speed is predetermined.”


Skip Barber, "Going Faster"

p 82. talking about trail braking "We have found that in most racing situations, it is advantageous to do so. The question is not if you are going to do it, but how."

Here are a list of links supporting exactly what I have been saying:

http://www.porschedriving.com/review_hebert.asp They teach trail braking at the Porsche Driving School … Say it isn’t so!
Brian Beckman PhD http://www.getfaster.com/Techtips/Physics23.html (did he say PhD?)
http://www.safespeed.org.uk/braking.html
http://www.panozracingschool.com/Racing_Exercises.asp )yes, they too teach trail braking
http://www.atomicwidget.com/Skip_Barber.html (taught trail braking a Skip Barber school)
http://www.bondurant.com/graphics/allTracks.pdf(another school teaching tb)
http://www.bondurantsuperkarts.com/courses.html (applies to carts)
http://www.perfectlaps.com/support/glossary.shtml
http://www.virtualracersedge.com/trail_braking.htm
http://www.perfectlaps.com/support/glossary.shtml (Freddie Spencer on motorcycle trail braking)
www.tarheelbmwcca.org/TRAIL%20BRAKING.doc
http://www.grmotorsports.com/topten.html
http://www.opentrackracing.com/112002_techtalk.html
http://www.rtrmotorsportz.com/rs_instruction.asp
http://www.microsoft.com/games/prec...cingschool7.htm

Hopefully, this will help. Hopefully.

 

CC I'm wrong about alot of things.... could you be more specific?

 

I don't think that's true at all. In fact, I think your DAS data is showing you that you can be too slow and yet you will feel a relatively high number of G's while turning.

Here's how:

You start by braking too deep. Now, let's think about what this means. It effectively means that you started braking too late. It also means that you will be further down the track when you come off of the brakes. This means that you will turn in later than someone who was on the brakes at the proper time. You have now just effectively shortened the radius of the corner.

Now, you will be also trying to trail brake into this corner. So, your car will be leaving the edge of the track as you try to make it turn into the apex. However, your car CAN NOT corner as well as someone who is doing no braking. So, your car will be drifting from the edge of the track, but not enough. Again, you are decreasing the radius of the corner.

When you finally get the car under control and really start turning it into the corner, you are driving a different line than someone who applied their brakes at the proper time. The line that you are driving has a shorter radius. However, there is no reason you can't drive that line at maximum G force. The difference is that you will be going slower because your corner radius is smaller than the other person's.

I think it is relatively trivial to brake late and turn-in while braking and maintain a high G force. In fact, I'd agree that it's relatively trivial to maintain maximum G force in that scenario. The fact that you have DAS data to show that you can do it after only 3 DE events shows how easy it is.

Now, as I mentioned in an earlier thread, driving a late apex means that we are planning to reduce the corner radius a bit. As such, many corners can take a SMALL amount of trail braking. And, the more I've thought about it, the more I think it should be trail SLOWING, not trail BRAKING. The difference is that your foot might be on the GAS and you are slowing down (due to the scrubbing effect of turning the tires).

How do you define unnecesary? Our driver who brakes too late might have a higher overall G force than our correct braker. Was his G force creation unnecessary?

 

Hmm... just had another thought.

Our late braker is going to put on his brakes later, shorten his corner radius, and effectively leave the corner sooner than our correct braker.

So... while the late braker and the correct braker might both experience maximum G force throughout the corner, the corner lasts longer for the correct braker.

So, over a set period of distance, the faster guy might have a higher G sum value.

 

Color,

It seems that every other person who has posted understands this. All your evidence supports the premise that we all pretty much agree on - Riding the edge of the fc - but only when the acceleration is in the appropriate direction - is the jot at hand. Light trail braking accomplishes this, but there are many corners where this costs you time.

The part you are standing firm on, that I think everyone else disagrees with, is that integrating the g-sum (or summing the sum) has little to do with a fast lap. Again, I will assert that if your theory works, there should be no need to require no zig-zagging or other extra motions. If it had a real correlation, then it would account for that.

If your theory worked, then we could put a computer in the driver's seat and it would be faster than Schumie.

Now here is another theory with a strong correlation coefficient:
Wearing a red drivers suit with Ferrari logos makes you faster. Just look at the F1 results for the last few years and tell me that does not have a very strong correlation coefficient.

 

Mark
That insight is true genius.
But you left out a very important factor.

There must be a lot of people present with their faces painted red, and waving banners and a very short man named Bernie being given lots of money.

 

Color -

Using Vic Elford's definition of of trail braking changes things a whole lot. I think everyone here agrees that initiating turn in while fading off the brakes is the right way for almost every turn. In fact, I said exactly that over on the 996 TT thread about trail braking. I am not sure how many of us agree with Vic's definition though. Again, since (on the 996 TT thread )we were talking about trail braking all the way to the apex I attempted to define trail braking as something different than imply starting the turn as you gently come off the brakes.

As for "Going Faster" they point out the use of TB in certain but not all turns at Laguna. We all need to keep in mind that there are two uses for trail braking - 1) going faster into the corner and 2) protecting your line in a race which often involves going slower but keeping your competitor behind you. This explains the quote you cited which appears contradictory to other parts of the book. The use of brakes deep into a corner has been mentioned by a number of racers on this thread. In a race finishing first is more important that going fast. To pass a car the most common technique is to pass under braking - attempt to brake later and get inside the front car. You will be off line and slow but, importantly you are in front. Trail Braking is the most common prevention technique. I think the hard core racers here will confirm this.

In sum, we should a) agree on a definition of trail braking. b) separate the use of trail braking as a defensive move from its use in an attempt to maximize speed through a corner. Make sense?

Regards,

 

I'm going to sew a Ferrrari emblem on my Sparco, and start puffing Marlboros.... thanks for the tip.

Seriously, I agree with everything Vic Elford wrote about trail braking... I'm sure he'd be proud to know that.... here's more....

Trail braking also helps you manage the weight transients as you enter the critical turn-in portion of the turn.... braking compresses the suspension forward... turning compresses the suspension side to side. Trail braking keeps the suspension load on the outside front tire stable as that transition occurs. If you were to lift off the brake the suspension was fully compressed under cornering, the suspension would release, and then have to be transisioned back to full cornering causing a "pogo stick" effect... unbalancing the car at exactly the worst possible time...

This is why some people say trial braking helps "rotate" the car. What actually happens is that the cornering capability of a tire increases as the vertical load on it increases. By keeping the weight forward, the tire has more grip... ditti less grip on the less loaded outside rear.

Trail braking is one of those rare driving things... an unmixed blessing

 

Interesting, guys;

I think we're closer to coming up with a "REAL WORLD" model, although I think it will be as diffuse and vague as the definition of trail braking. It will basically say, "go out and see what you can do. We'll be watching the watch!"

I tend to find the most use in the Carroll Smith quotes. The fact that he does not mention how one accomplishes this task is probably not an omission on his part - he being flat out BRILLIANT - as he is quite sage enough to know that there are infinite combinations to achieve it which cannot be calculated until the driver actually TRIES THEM.

The definition of trail braking is STILL a big problem, and to say that it means any braking done after turn in is NOT sufficient to describe differing scenarios. I still MUST draw a distinction between "Rotational Braking" and "Balance Braking" Note that Elford does not go into any specifics as to how much or in which corner. He simply describes a very broad application of TB.

Milliken comes the closest to espousing what Color is offering, but even they do not specify how this is achieved, or what percentages of which input need to be applied at any given point in the corner.

Another distinction that must be realized is that many times writers are talking about door-to-door racing, and this type of driving is FAR different than simply lapping (what most of us are talking about). The former will NEVER be as fast as the latter, properly done.

What we have all been trying to say is that - with our considerable experience - it is all too common - and nearly universal - for a novice driver to expend FAR too many Gs in braking (too late) and turning, and then not have any left for proper apexing and acceleration. This is not even to mention that novice drivers - in their "Unconscious-to-Conscious Incompetent state" - do not realize that it is THEY who are creating this "backwards G load" scheme, and that they do not have the SUBconscious skills to deal with such a cornering scenario.

Since the goal will ALWAYS be to exit as fast as possible, the entry must be tuned to this goal. Minimum side-load scrub is crucial. Getting into a corner with the highest speed and the LEAST amount of Gs expended will translate to good exit speed. Maximize this ratio further, and you create "free speed!"

Color - Here's a thought. Since you have limited time by your own admission, work out a trade with your family. Offer them all the CONSIDERABLE time you must spend researching these detailed posts and pouring over printouts and manuals in trade for increased seat time!

 

That's good. If everyone pitches in, we could get perfect correleation and all be really fast without having to practice at all.

 

Since this is all about a Fastest Driver Model, remember in our perfect correlation that David Coulthard is almost always seen with a model, and he's a fast driver, or he used to be.

 

As long as we are giving away all the secrets, I can tell you that blue splitters attract bunnies.

 

ColorChange, if you can set up your DA to record segment times, it would be interesting in your next outing to record the data at a school that does the no-braking exercise (several BMWCCA schools do it here in the Southeast). I'd be interested in seeing the time differentials between the no-brake sessions and the normal sessions taken from some point prior to entry to after exiting the turn on a handful of turns. Obviously, lap times would be a somewhat worthless comparison but the segment times immediately preceeding to exiting the turns should have a lot of useful data if you can record them that way. I don't have the math expertise to argue what models work better but I think as in all things that take "feel," there is a difference between what hypothetically could be done and what an individual can physically do.