Not much going on in this area for awhile, which is too bad. I have a couple questions, hopefully someone can answer. How does trail breaking help rotate the car in turns? What type of turns should it be used in? And any other info you have.
Thanks

 

Only if you keep hitting the trees. Using a chain saw first usually works best and makes turning easier.

 

I think trail braking causes a shift in weight distribution. It puts more of the weight on the front tires and thus allows it to grip a bit more or it takes a bit of weight off of the rear giving it less grip. The momentum of the car around the corner will cause the rear to slide more and thus bring the rear out and rotate the car.

Correct me if I'm wrong guys. I'm just applying some physics here. No real world experience or anything.

 

badtziscool has the basic idea right. The conventional way of driving is to get all your braking done in a straight line before the turn so you can use all of the tires' power to turn-in and then accelerate through the apex.

But over the past 20 years or so, trail braking has been proven to decrease lap times when compared with getting the braking done before turn-in.

You counter the tendency to understeer (since you're braking AND turning at hte same time) by transferring weight to the front and giving the tires a little extra gripping power. Since you take some weight off the rear tires, the rear end of the car will find it easier to continue in the direction you were travelling prior to turn-in. When you release the brake pedal, weight will shift toward the rear of the car before the rear tires have enough traction to continue at that angle and you'll get rotation of the rear end. Quickly countersteer, and once the car is pointed to track-out, get that gas pedal to the ground.

You'll have more success with this if the front tires have massive grip. Running a staggered setup like the G35 coupe will make it more difficult to get rotation. This is not to say that you can't get a staggered setup to rotate. I can tell you it's quite easy for me to get a Viper to come around and it was on 275 fronts with 315 rears. Of course with 275s up front, there's plenty of grip available...

Trail braking is a fairly difficult (and definitely dangerous) technique because the difference between getting some rear-end rotation and ending up with flat-out understeer is fairly small. Remember that the tires have limits, so the amount of steering and amount of braking you input cannot exceed that limit. If you do exceed the limit, you'll drive straight off the track. Also, if you release the brake too quickly the front tires will not have enough weight on them, which will also result in understeer.

You're going to have to be able to brake correctly in a race situation. You want to be on the brakes at 100% (without ABS/lock-up) initially and then start releasing the brake pedal as you approach the turn and turn-in. The common habit developed from street driving is to brake lightly and increase pedal pressure as the car nears the turn. Braking at full power initially on the street would result in a lot of rear-endings, so this habit is understandable.

If you have an opportunity to practice trail braking on a skidpad (highly recommended), you'll find it easier to initiate rotation if you take a bit of a circle route turn-in. This is a good way to get the car to rotate when you're first learning; you can practice skid recovery here. Remember that when travelling uphill, you'll need more entry speed as the weight of the car is shifted toward the rear because of the uphill incline.

Trail braking is an important technique to improving lap times, but it is not the first thing I would work on. It is a high-risk technique because you'll be entering turns faster and braking much later, which means running off the track if you mess up. I would work on (1) being smooth, (2) getting the right lines, and (3) getting on the gas earlier out of turns before diving into trail braking as you'll almost certainly find more time saved in those areas, and those three areas are far less risky than trail braking.

 

it is absolutely necessary while trail braking is easing off the brake. To abrubt will cause a spin out, causing for mor correction, and loss in lap time.

The G35 responds well to trail braking, and late braking on entry in transistion to trail braking on tight low speed corners.

 

Yep, the faster you release the brake, the faster the rear end is going to come around

 

Thanks for the great info. I was planning on trying this technique in slower speed/tight turns on my next track day. Sounds like I need to be careful though.

 

Very careful.
There is quite a bit more margin for error with straight line braking, and by definition, done to the optimum trail braking takes you to edge in the transition from straight to turn in and again from turn in to middle corner.

Your tire has a finite amount of grip. In a straight line, especially in a formula car where you can actually see the tires, it is not that difficult to determine the threshold of braking pressure beyond which the tire loses its adhesion....it locks up and starts to slide.

When you turn you increase the amount of demand you put on the tire, so it is easy to see that when you turn the wheel, if you are at threshold braking pressure, you must slide unless you remove enough demand from braking to compensate for the demand caused by turning. The tricky part of course is that the "balance" of the car is dynamic and changing too. So you need to understand the set up and get "feel" for how it behaves. There will be some turns on the track where a mistake will not matter much. Those with walls and stacks of tires are not among them.

What the technique does is allow you to initiate your braking at a brake point that is deeper down the straight....thus carrying higher speed down the straight for longer, and decreasing lap time.

However, it then requires that you gently lift off the brake pedal just before and as you initiate turn in, to stay as close to the maximum adhesion limit of the tires as you can.....but if you are a little bit over, you have almost no room for recovery, depending on the type of corner conditions you encounter.
Depending on the balance of the car you may understeer or oversteer...Though trail braking does have more "plant" on the front at turn in than a car that has been straight braked, the braking force obviously promoting a weight transfer or "pitch" forward, as contrasted with a slightly rearward pitch for a straight brake car that has applied just a touch of throttle to sit the rear down in the turn, that does not necessarily mean that the car will oversteer as opposed to understeer(get "loose" as opposed to "push"). Each car is different. So rule one is get to understand your car before you mess with this on the track, and work up to it gradually.

There are three parts to every turn. You cannot discuss trail braking without discussing turn entry or turn in. IF you go in to entry too fast, it will very much cost you in recovery work critical speed in mid turn, and therefore potentially negatively impact your ability to attain the highest velocity on turn exit. AND TURN EXIT SPEED is what is much more important. That velocity is carried with you all the way down the ensuing straight. It is less important to maximixe turn entry speed than it is to maximize turn exit speed. So all of this trail braking stuff is ASSUMING you can manage to attain equal or greater turn exit speed. A lot of drivers "hero brake" and then butcher turn entry, consequently mess up their ability to maximize speed at exit, ultimately just abusing their equipment and going slower.

SO, work on your turn exit first, then your turn entry, and finally your middle turn techniques. I think that trail braking is generally a "good thing"...but not for every corner or situation, and not without a well refined feel for what the car and tires are going to do, matched with some recovery skills to get out of a pickle you can put yourself into.

Hope that helps.
Have fun, drive safely.

 

Eagle 1, your the man.
Thanks again.

 

A great, inexpensive paperback book that covers the approach to managing your turns is Alan Johnson's "Driving in Competition". Short, to the point, and very clear and practical.

The next book I would get is the the book from the Skip Barber school called "Going Faster". That is much more detailed, but as good a summary on a variety of techniques that I have seen in recent years.

Most books by famous drivers are a capitalization on their fame and have a lot of history and pictures, but are short on good stuff to actually help you drive better.

 

I've got the Going Faster book and DVD...another thumbs up from me. I think this is a good book too -

 

There is another element here that probably deserves some discussion, and that is left foot braking. Anybody want to jump in on this extension of the discourse first, and how it fits into the next level of trail braking technique in managing either single or compound turns?

 

i usually do it in those situations or lightly on it in chicanes.