RedlineMan

OK all you TB Pros;

Give me a good primmer on how you do it? Give me ideas on how you modify your line from a classic Slow In-Fast Out, to a serious and successful TB line. Do you turn in sooner to give yourself more ooops room? Do you go in later to counter pending rotation? Fill in the blanks for me here.

I think this may be the first time that I have aksed a question on Rennlist. After this, I WILL know it all!

Skip Wolfe

Also how many trail brake with left foot braking as John suggested in the other TB thread vs using the right foot. Seems like it would be smoother to just leave the right foot where it is since you are transitioning from hard straightline braking to TB. Whereas with left foot braking you would need to transition from straightline braking to TB AND transition from right foot to left foot braking.

This is good stuff by the way. Even though it has been a bit heatedfrom time to time, there has been more meaty discussions here lately than I have seen in a while. Makes people think which is good.

Bob Rouleau

John,

Where I trail brake (not ALL turns) I describe it as follows:

Not Trail Braking- I initiate turn-in as my foot comes off the pedal, taking advantage of the larger contact patch. This is a very gentle release of the brake pedal because I am trying to avoid transferring weight abruptly this transitions into a constant speed (maintenance throttle) until I can squeeze on more power.

Same turn, Trail Braking - I do less initial braking and I release the brakes more slowly such that I am off the brakes well after the turn-in point. The release of the brakes is largely a function of keeping the car in balance - there is room for subtle adjustments in the release phase as long as nothing is done abruptly. Depending on the corner, there is little time spent at maintenance throttle compared to the not trail braking technique. If you go to LCMT, I trail brake at the Four, Eight, Ten, Bridge and Namerows. I do not turn in early because in my car at least trail braking does not make the car understeer.

I suspect this is totally obvious to you and I probably haven't dealt with your question very well.

Rgds,

carreracup21

I'm sure there are better folks out there than me to try to answer this question, but I'll tell you what I do ( certainly not presuming to be more experienced ). I think the most important thing is to ask "when" more than "how" as the biggest advantage to using it will also be in the easiest corners to use it. A easy place to start using TB is a decreasing radius corner at the end of a straight. I use my right foot, but I'm sure there are advantages to using your left so long as you don't have to simultaneously downshift. I tend to get my heavy braking done early then simply taper off gradually as I make my way towards the apex. This effectively lengthens the straight and allows you to get closer to the limit earlier in the turn where normally you would have quite a bit of reserve traction you were not using. The tail of the car will get a bit happy, but it's usually pretty easy to control by just opening the wheel slightly and decreasing your braking force to counter the induced oversteer. I tend to let my line drift slightly wide in the turn then tighten as let off the brakes and hit the decreasing radius. I tend to catch a lot of people in the corners and braking zones I use this technique so I'm sure it's faster. I think the key is starting off with a light touch on the brakes to get a feel for what the car does. I was surprised by just how much you can get away with and I'm in a 911. Just go easy starting out.

Larry Herman

I'll bet this is going to be a long thread too. The last one on Trial Braking jumped to 5 pages in 2 days! I'll go first to give everyone a platform on which to disagree (note: I was going to be first but it took me so long to write this that Bob & carreracup21 jumped in front of me)

First, the tighter the turn, the more you will want to trailbrake. For the hairpin at Summit Point I dive into the turn hard on the brakes and have the rotation of the car pivot me around the turn. At the mid-point of the turn the car has slowed enough to pick up the gas and accelerate out of the turn.

Second, the more the turn radius decreases, the farther you will want to trail the brakes into it. Once again it is the rotation thing. Plus you want to go really deep, and turn the car really hard so that you can power out. The only way to do this effectively (read: not give away entry speed) is to TB.

Third, the faster the turn the less you will trail the brakes into the turn, and the more gentle you should be with them. Getting rotation on the car in a slower turn is helpful. Rotation in a fast sweeper is not. You want to drive the car through them with the car as stable as possible.

Here's what I do for the typical turn that I want some trail braking. I brake late (as usual) and start to lighten the braking just as I turn into the corner. I am hopefully maintaining the front tires on the edge of the friction circle. As the car slows I continue to turn the wheel more until I have reached my total desired steering input. This process is done as smoothly and as slowly as the turn wiill allow but usually over the time frame of about a second or two (max). At this point the rear of the car will be starting to get loose as the car is rotating, pointing me towards the apex. This is what I call the transition point of the turn. I then get back on the gas hard. This stops the rotation, and plants the tail of the car. I am now accelerating towards the apex, but it is my rear tires that are now on the edge of the friction circle. As my speed increases I have to slowly unwind the steering wheel in order to keep the front ahead of the back (remember that as your speed increases, the arc that you take must increase too). Hopefully, I have picked the right line and I am flatout past the apex out to the edge of the track and down the straight.

With this technique, I am going in very fast, the slowest part of my turn is in the beginning at the transition point. It is also where I am truning the car the most. From that point on it is accelerate out and unwind the wheel...fast in-fast out.

One final point for those of you who keep missing it...I do not do this for every turn. There are some turns where I only want to brake in a straight line. Turn 10 at the Glen is one...it's just a tap and go. And there are some turns that I gently drag the brakes into. And then there are the turns that I trail brake the **** out of the car to get it to rotate. Practice this carefully and good luck!

ColorChange

Since I have such little experience, especially good experience in the Pcar, I will not comment. Hopefully I can when I get back from Putnam and have data to back up what I say. Right now I don’t.

Larry, well said.

sjanes

This should be an interesting thread The driving style of different drivers is probably going to vary significantly based on their past experiences. Were they taught trail braking by an instructor, or did they learn it on their own? Did the instructors in their region believe the idea is "crap" (as one Mosport instructor told me) and suggest students not try it at all? It also depends on the track. If you learned to drive at Mosport, you probabaly trail brake very little if at all. If you learned to drive at a small twisty track, you may trailbrake everywhere.

At Mosport, I release the brakes during turn in and get back on the gas for throttle maintainence to the apex at almost every coner. I use it a bit in 3 to get the front end to grip on the concrete, but that's about it. For corner 9, I trail in a bit, but I find the inside curb more effective for rotating the car. Tremblant however is a different story. I carry the braking farther into 4, and actually coast a bit, using the friction of the tires to slow the car before getting back on the throttle. Corner 8 is similar, but I'm off the brakes a little sooner. At The Glen, I trail a bit at the turn in to the bustop, but I can't think of anywhere else I do it.

For the corners that I don't trailbrake into, I'm releasing the brakes on turn-in to balance the car. I personally don't consider this to be trail braking as I'm only using the brakes for balance, not reducing speed (although some small amount of speed is obviously lost). I can't think of any corner that I'm on the gas before turn in except for the corners that are flat out (Esses at the Glen and 6 at Tremblant, etc). For corners that don't require braking before turn-in (the fast left at the Glen, 4 at Mosport) , I usually give a little lift of the throttle before turn in just to give the front end grip.

trumperZ06

" CC ".... You have... ALMOST NO experience, and it's nice to see you FINALLY realized it!!!

mitch236

Poor Color, let's lay off him for a while, I think what he said was very well put.

I was going to post a thread about trail braking this morning, but John beat me to it. But here is my question:

Let's assume a 90 degree constant radius turn at the end of a 1000 foot straight and leading onto a 1000 foot straight.

The turn is level and the surface is consistant.

I also want to define some terms so that we are all speaking the same language. Let's break down the turn into 4 parts:
1 The "brake zone" (this is on the straight only)
2 The "turn in zone" (this is where the car is initially rotated)
3 The "mid-corner zone" (this is the part of the turn where the car is settled on its arc, and includes the apex)
4 The "track out zone" (begins at apex and continues to the next straight)

My question is: Is heavy trail-braking really faster?

My thoughts:
If we were to look at each tire individually and map out its friction circle, then I think the most efficient use of the patch is to have the car as balanced as possible. Now when the car is under heavy trail-braking, the front tires carry the most load but have the highest fc available because downward g-forces have increased but at the rear the opposite is true.

If the car enters the turn under light trail-braking (enough to settle the turn in) the individual tire patches are more equal.

In the heavy trail-braking scenario, the car will tend to overrotate and will need to have many adjustments to keep it on line, where the second scenario would require much less input.

Which way is faster and why?

JCP911S

Good stuff above... interesting to see different ways people look at TB

Couple of thoughts to get started.

First, anytime you are in the brakes as you turn the wheel thats TB... (just my definition...) it is a continuum from a light brush on the brakes to tire-smoking threshold braking to, and frequently past, the apex.

Second, how much or little TB depends on your strategy for the turn based on where it is on the course. The geometrically identical turn will be taken very differently depending on whether it is at the beginning of a straightaway (light TB late apex, on the throttle early) or the end of a straightaway (heavy TB, early apex, feather throttle at exit).

Interesting note... turn 1 at the Glen is both... but the section through the esses is more important than the front straight, so you treat it like an entrance to a straight, not the end.

Third, Brake + lateral gs must be less than total grip of the tires... as you add slip angle you must decrease brake accodingly.... if you're only using 60% of the tires for turning, you might as well use the other 40% for braking.... if you set as your goal keeping the car perfectly balanced at the limit through the entry of the turn, you will naturally find the appropriate level of TB... too little and the car will bobble.. too much and...well you'll figure that out real fast....

Fourth, some degree of TB smooths the transition from brake to turn-in so based on my definition above you always TB to some degree any time you use the binders.

Finally, experiment gently with small steps if you are new to this. Find slow hairpins with lots of runoff room to practice... use a crappy old set of tires and keep an extra set of tires handy ... (but if your tires are flatspotted, give it a pass)....BTW the rears are probably more likely to lock-up fronts, so be prepared ... and boy, when that happens, its interesting... especiall in a 911

Have fun

mitch236

This is one of my contentions. I try to enter the turn as fast as possible, that means that I am using 100% of available traction to keep the car on its arc. I believe this to be the fastest way. I don't see how trail-braking past the "turn in zone" on a constant radius turn is faster. If there is any traction left over for braking, then you didn't enter fast enough.

sjanes

Mitch,

It also depends on the car and how it's setup. When I drove my Volvo station wagon around the track, I trail braked more since the car wasn't overly interested in turning. Not super heavy trailbraking (i.e. on the ABS), but I took longer to fade off of the brakes. Keeping some extra weight on the front wheels and off the rear wheels helped with rotation. Basically, if the car is naturally unbalanced during cornering (as most street cars are, towards understeer), I can use trailbraking to take grip from the back, and give it to the front. My 911 is different all together. I setup the car the way I want for each track I go to, so I use trail braking a bit in the slower corners for rotation, but not near the extent required for my 3400lb Volvo.

Larry Herman

NO, for that example it will not be faster. To dissect your premise from above in numerical order:
1 - I brake as late as possible squeezing on the brakes to maximum, and downshift (if needed). As I approach the turn-in zone I start eazing off of the brakes (if I can).
2 - I turn-in while still eazing off the brakes.
3 - I have transitioned to the gas, and it is to the floor.
4 - I unwind the wheel as the car accelerates, and drifts at full throttle out to track out.
5 - I look in my rearview mirror to see how ridiculously far ahead I am of the "heavy trailbraker"

JCP911S

Mitch;

The sequence as Larry laid it out is correct here, because this is a Type 1 turn (leads to a straight). Maximizing speed down the 1000 foot straight-away after the turn is the most important priority, so light trail braking, later apex, early on the gas is the deal....slower in faser out...trade 50 feet of entry speed for 1000 feet of exit speed.

If this same turn led to a bunch of slow speed esses, you would trail brake heavily on an earlier apex. THis would allow you to move your braking point deeper and extend the straight-away.... potentially you might actually brake through the apex, and "throw the exit away". Since exit speed doesn't help you much going into a bunch of slow squigglies, the late braking allows you to stay at full throttle longer and gives a faster overall laptime.... fast in slow out.

Also as to the Brake + Turn-in question, as you turn in, the car does not go immediately to Max lateral G... generally it starts at zero G right at turn in and increases to Max G somewhere around the apex. During that period while the tires are building up to Max G, you can use the additional grip to continue braking... easing off the brakes as lateral Gs build.... if you are Shumacher, Brake G + Lat G is 100.0% of the tires total G grip at all points.

sjanes

OK, if we go with the definition of trail braking being "anytime you are in the brakes as you turn the wheel", then I guess that I TB into any corner that I apply the brakes before entering. This includes corner 2 at Mosport where I am finishing the last few % of my brake release as I'm turning in. I spend a lot of time working on the smoothness of my brake release, so my release may be a bit slower that others. I prefer to consider this to be "contact patch management" as my goal isn't to slow the car. For Mosport's corner 2, I'm an on the gas before I finish dialing in my steering input.

So, does anyone get fully off of the brakes and onto the throttle (either accelerating or neutral throttle) before a corner?