To trail brake or not...
 

This seems to me to be a big controversy. Some professional drivers never do it. Others say it's the only way to be fast.

So, what about you all? Do you trail brake? Under what circumstances (car, setup, corner, etc.)?

Trailbraking is is merely a way of smoothly transfering grip from the front to traction in the rear.

For example, if you mash the gas, the rear sinks low causing traction. OTOH, if you stab the brake the weight transfers to the front of the car causing the front to grip more. Good techinque of weight transfer will definately make for faster cornering.

I should have also pointed out that trail braking is directly proportional to steering input. That is to say, the more you turn in, the less you brake. This forces the grip up front (from weight transfer) to increase WITH the added steering input.

Lightening (via brakes) the back will also help rotation.

FWIW, you might want to get a reprint of this: http://www.high-performance-driving.com/ summer 2007 issue. Trail braking is described in detail.

I just came back from the print shop... peckerhead wants $5 a page to scan it, otherwise I'd put it up for you.

Just to clarify, I wasn't asking for a how-to. I'm rather familiar with weight transfer and its effects. I was just wondering what other people do, when, and why.

So I take it you love to trailbrake?

I remember reading in a Corvette owner's magazine, an ALMS drivers was interviewed. He had three tips.

'One, always look through the corner. Two, wind out steering and slowly apply throttle as you exit a corner.'

Okay, pretty obvious, I thought. The third one must be pretty obvious, too.

'Third, never trailbrake'

OK... wtf? I guess I was wrong...

And in fact, I've heard that there are some racing schools out there that don't teach it.

It depends on the car. You gain more relative time trailbraking in a spec miata than in a z06 vette, because its all about momentum conservation.

Some people think they trail break but actual trail braking is about as close to the limits of adhesion as you can get and a very difficult thing to use to your advantage.

I have been doing HPDE events for nearly 5 years and i am just starting to dabble in it, in no way do think i am really getting anything out of the technique yet....

There is a school of thought that you are either full on the brakes, or full on he gas. Anything less is slow. I'm not saying it's right, but I've heard it before.

However, IMO, trail-braking really depends on the track. There are some tracks which force you do it at least a little (indirectly). Keep in mind that guys who drive the endurance races are also trying to save their brakes.

Jason Saini who walked away with the 2007 MX-5 Cup Championship trail brakes the heck out of his MX-5. He has taught me to do the same with my 2nd Gen. Drive as you wish.

I often find it useful on particular corners.

One corner that comes to mind is Big Bend at Lime Rock. I loved carrying a lot of speed into that set of turns and easing into the first part of Big Bend with trail brake. This was in an FC and FD and a turbo Miata.

At buttonwillow there was one medium speed left turn (that I distinctly remember) before the esses that felt better to me if I trail braked into it. I think there were a couple of others but I can't picture them right now. In contrast, the end of the straight didn't not feel good at all when trail braking. The car is moving really fast down the straight and its a real tight, slow corner. Felt best to finish the braking hard in a straight line.

When I first learned to trail brake, it was by accident. I was carrying too much speed into Big Bend in my turbo FC. By trail braking, I was able to keep traction/adhesion balanced on both front and rear tires as I turned into the beginning part of that turn while also decreasing my speed sufficiently to not spin. I was totally at the limits of tire adhesion. By the second part of Big Bend, my speed and car placement was appropriate to allow me to take the rest of the turn very quickly. That was my fast lap of the day - and luckiest.

Orly?!?
 

Mahjik - I can see why you wouldn't necessarily agree with that philosophy. Advocates of that philosophy might be correct if only longitudinal acceleration (acceleration and braking) is taken into account, but what about lateral acceleration (cornering)? Even if we don't consider the effects of transient stability and control (which is damned complicated, and can wait for a later discussion), we can't ignore the fact that steady-state cornering is a part of almost every corner.

Take a look at this picture I got from http://www.temporal.com.au/FIG2.gif.
I'm sure any racecar engineer is familiar with this diagram. The goal of the racecar driver is to keep the tires on the edge of that circle (or blob - it's rarely a circle), to maximize acceleration in the appropriate direction. We can call this 'optimizing' acceleration, for discussions in the future that may pertain to this subject.

"Driving a car as fast as possible (in a race) is all about maintaining the highest possible acceleration level in the appropriate direction."
- Peter G. Wright
Technical Director
Team Lotus

I think you might be hard pressed to find a racer that disagrees with Mr. Wright.

So, I agree with gracer7-rx7 and RockLobster in that it largely depends on the situation...

What do you all think?

One thing to consider is that (as I understand it) trail braking will keep the front tires more loaded on turn-in, which will help if you tend to push a little on corner entry. On the otherhand, if your car tends to be a little tail happy, you probably don't want to make the rear any lighter.

I've played with trailbraking a little. Sometimes intentionally - T16 at VIR, to smooth the transition into full throttle through Hogpen. Sometimes unintentionally - when I have overcooked the braking zone into T1. ;)

As a technique it seems dependant on so many factors, the car, the drivers style, the track, the weather, et. al., that making general statements about its efficacy is of limited value. Certainly it's something you may want to play with while out on the track, but I see there being any one great truth to the question of trail braking.

-bill

btt

I always trailbrake. I think it's genetic.

I will also left foot brake to help the car rotate or to settle the car in low grip situations - especially on snow.

Which is what I said if you ready the post in it's entirety:

I think gracer7 hit the nail on the head that it can be useful in *particular* corners if used correctly. I learned how useful it was the same way: by accident, when my brakes were fading and I carried way too much speed into the corner than I meant to.

Something to consider is that it allows you to brake slightly later, thereby compressing your straight-line braking zone by extending it past your turn-in and allowing you a little finer control over the speed you carry into the corner if you're straight-line braking and timing aren't absolutely perfect like mine aren't. What I mean by that is if you only brake in a straight line, you have to hit the timing at the start of your braking zone perfectly, threshold brake perfectly and be off the brakes right when you want to turn in and hitting that magical combination of timing and pedal application is tricky. By braking into the turn you will be able to absorb slight miscalculations but still maintain control. But then again, I'm a n00b and I stink at trailbraking too so take that as you will.

won't trail braking raise the probability of over-braking and sending you out of control? You start trail braking, realize you might be in a tad hot, apply a little more force and then understeer if you do it too early in the turn or oversteer if do It too late?

Can't tell very well but could this guy have trail-braked too much at the end?
http://www.youtube.com/watch?v=FXpRYLzsMxE

Well, it "could" cause you to loose control, yes. Since you are braking, you are removing weight from the rear of the car. As you begin to turn, with less weight in the back it can loose traction much easier. This is why it is a specific technique. i.e. to be able to brake later into the corner and continue the breaking into the turn in without spinning out. When used right, you can have a much greater speed into the turn.

the whole purpose for trial braking is to balance the car through the turn, all ur doing is using another tool to do so. . . ur left foot. its not just for shifting, lol. when you left foot brake if u are timly and gentle you can control the motion of the rear end. usually when ppl go into a corner they are heavy on the brakes forcing the weight to the front, this lightens the weight in the back causing, in some instances, oversteer if you can left foot brake and have a grasp of weight transfer you can shift some of the weight back to the rear giving you better grip while exiting the turn. if there is too much weight in the front and u fear understeer and/or oversteer you can lightly pull up on the handbrake which will anchor down the rearend taking weight off the front allowing for a smoother turn. did this in my dads 88 honda accorrd around a 15 mph chicane in the wet at 30+ which isnt super fast but hey it had stock totally blown marshmellow suspension so i think it went pretty well lol

Left foot braking is an entirely different technique than trail braking. As far as using your hand brake on a race track... Unless you're in a rally car on a super special, I'm not even going to go near that one.

In my track experience, I would trail brake through the slower corners because it allowed me to carry more speed through the turn and cornering speed was important. Anything that was wider than a 90 degree turn or faster than about 50 mph it was faster to get on the gas lightly before turn in and feed in the gas through the turn to stabilize the car. This technique forces the car to push so turn in would be earlier and I can still clip my apex while letting the car float wide. When I trail brake in those corners, turn in would be unsettling the car because the back would be hella light and I would also come out of the turn slower because if I started to accelerate at the wrong time the back would snap loose, so I had to wait for it.

like i said in an earlier post i consider it to definatly fall under the category of trail braking. why wouldnt it? explain your theroy.

its not like ur yanking the fricken handle w/ all ur force, ur just tuggin it a lil for force weight to the rear when youve under estimated the corner or if theres some slipage in the rain. dont know how much it rains in virgina but over here its nice to have a resort that doesnt include u in the sand pit or in a group of trees near a cliff. seen many profesionals use the e brake to counter poor front grip or trecerous conditions

How does tugging at the handbrake shift weight rearward???

I might need more practice then because I tend to understeer (not enough braking) and then have to try and pull out of it at the last second which just means a slower exit in the end. I'd rather slow down enough before the turn and accelerate out of it.

I'll take a more vids at the next track day so I can compare.

LOL at the e-brake shifting weight backwards. Maybe when you've spun out and are rilling backwards.