PCA SDR

Ok, so about this trail-braking thing...

What is it?

If it's continuing to brake as you enter a turn, what makes it different from braking late? Do we teach braking in a straight line just because it's easier to focus on separate distinct tasks? Is the point of braking as you enter the turn to continue slowing the car or to control the rotation? Or is it just a cool pucker factor?

Edumacate me.

Trail braking is - when you are so far off of the track (course) that you only see a trail through the rocks - you should brake!

Nice one Chuck.
I think I learned that at Fontana.

The real answer is yes, trail braking is simply braking while in the corner. Unfortunately, it isn't all that simple. First, it is hard to do well as you are balancing the limited grip. Too hard on the brakes and you spin, not enough and you don't make the corner. Second, while trail braking, the tires all have very different grip levels, so the inside rear locks in cars without ABS, and even cars with ABS often have reduced braking power. Third, trail braking is very ineffective as hard braking would result in a spin, so it doesn't really slow the car much. Straight line braking on the other hand is very effective.

BOTH techniques are needed for very high level driving, but straight line braking will get you 90-95% of optimal in most corners. Easier, safer, more repeatable, and pretty effective, that is why we teach straight line braking.

As you may have figured out, I am a BIG fan of straight line braking. I like the slow in fast out that it encourages. I think the best use of trail braking for most corners is after 90% of straight line braking to force rotation on corner entrance, not for slowing down.

If you would like a more detailed explanation/demonstration find me at the next AX/DE/TT.

Hope that helps.

Jad wrote:I think the best use of trail braking for most corners is after 90% of straight line braking to force rotation on corner entrance, not for slowing down.

+1

Jad’s comments echo the PCA performance driving school of straight line braking.
When you have that wired….
The first turn at a track I might trail brake would be the Type 2 sweeper at the end of a long straight.
I think Mario A said something about how he judges a driver by how they release the brakes (control the weight transfer).
I left foot brake, unless I’m shifting my left foot is covering the brake pedal.
So I tend to trail brake everywhere I can, it has helped with my car control.
Note the newer Porsche electronics will just cut the engine to idle if you try to feather throttle and brake simultaneously.
This book was a big help, includes good discussion about the drawbacks of threshold braking too.
Going Faster! Master the art of race driving. It’s from the Skip Barber racing school.
http://www.amazon.com/Going-Faster-Mastering-Race-Driving/dp/0837602270
It's been a great resource.
cheers.

Mike, thanks for the link - that's one well received book! It's on my short list.

Jad, thanks for the invitation. I'll definintely take you up on it - I'll keep my helmet with me at start/finish so I can jump right in when you show up. Apologies in advance to any student you may have in the car with you at the time

As Jad said, trail braking is "trailing" the brakes into a corner.
If you think of the total available traction being 100%, you should be using all 100% braking in a straight line, and all 100% in steady state cornering. All fine and dandy, but what about corner entry, and especially long decreasing radius corners?
SO...if you release the braking load at the same rate as you apply cornering load so that the vector sum load always equals 100% you will be using ALL of the available traction during corner entry and keep the suspension smoothly loaded to avoid "spikes" in tire loading (just like you do exiting a corner by feeding in throttle as you straighten out to keep the rear tires smoothly at the limit of traction).
This is a simplistic, ideal view of course because there's always some other real-world issue like rotation, intentional weight distribution, brake system misbehavior, and so on that may take precedence over the theoretically ideal use of the available traction. Trail braking is an advanced technique, and, like heel-and-toe, not taught in our schools because it's too confusing to entry level drivers who are just trying to keep it between the cones and remember to breathe at the same time.
Achieving a chassis setup that allows trail braking to be used to your advantage is one way races are "won with wrenches"

Take that ride with Jad and you'll see how it's done by an expert.

BOTH techniques are needed for very high level driving, but straight line braking will get you 90-95% of optimal in most corners. Easier, safer, more repeatable, and pretty effective, that is why we teach straight line braking.

As you may have figured out, I am a BIG fan of straight line braking. I like the slow in fast out that it encourages. I think the best use of trail braking for most corners is after 90% of straight line braking to force rotation on corner entrance, not for slowing down.

+1.

Straight line braking is, IMO, the only type of braking to be done for effective performance driving when at a lower level of driving skills. Until one starts learning advanced, nuance techniques (Heel-Toe Down-shifting, Trail-Braking, Purposely Pitch-andCatch mid cornering, etc), Trail-braking should be omitted until all the other basic skills are learned, memorized, and executed instinctually when on a course. In particular: smooth inputs, use of the course, looking FAR ahead, and understanding the line are far more important than Trail-braking, heel-toe, etc., IMO.

This is why we emphasize straight-line braking at the PDS and refere to Trail-braking as an advanced technique to be learned later.

I'm 100% in Jad's school of thought on this.

My 2-cents.

For trail braking(threshold braking) to be effective in rotating the car you really need a LSD with a high lockup ratio. GT3 cups have a 40/60 diff (60 is the lockup ratio under deceleration), and many racers use Guard's 50/80 diff. With an open diff you're just waisting your time and tires....

As Jad said it's an advanced technique that was taught to me by a pro many years ago. It takes lots of practice (on a empty track) and even then it's hard to master effeciently. Scrub off too much speed and you leave yourself slowed at exit, conversely too little brake and you're spinning perhaps off into the boonies. When performed by a pro you can see (from the right seat) how effective trail breaking can be in getting thru a corner. We worked on it at BW for an entire day mostly at Sunset and Sunrise, but also going over Lost Hills which requires a lots of patience. I met the Lord on several occasions out in the fields. Bring a strong vacuum or leaf blower(they work great)....

Let me add that I would suggest working on a skidpad with your car to get a feel for how it handles at the limit. There's far more car control to be learned there than most driver's take advantage of. I'll be testing a new Spec 996 at BW tomorrow and the first place I'm going is to their skidpad over by the cart track....

[quote="jrgordonsenior"]For trail braking(threshold braking) to be effective in rotating the car you really need a LSD with a high lockup ratio. GT3 cups have a 40/60 diff (60 is the lockup ratio under deceleration), and many racers use Guard's 50/80 diff. With an open diff you're just waisting your time and tires....

I disagree, it can be done in any car. I do it in my front wheel drive H stock car, my AWD G stock car and in a 944SPEC w/out LSD and last weekend in a prepared 911 with LSD. its the same basic concept, you just need to adjust the most important part of what makes the car fast.... the driver.

Be prepared to be slow and make lots of mistakes while learning to do things like trail brake or left foot brake. It takes practice.

Personally, I need little preparation to be slow. It seems to come naturally. But then, some people are blessed.

ME TOO! THATS WEIRD.
Maybe it's a north county thing.

MTrotter wrote:

jrgordonsenior wrote:For trail braking(threshold braking) to be effective in rotating the car you really need a LSD with a high lockup ratio. GT3 cups have a 40/60 diff (60 is the lockup ratio under deceleration), and many racers use Guard's 50/80 diff. With an open diff you're just waisting your time and tires....

I disagree, it can be done in any car. I do it in my front wheel drive H stock car, my AWD G stock car and in a 944SPEC w/out LSD and last weekend in a prepared 911 with LSD. its the same basic concept, you just need to adjust the most important part of what makes the car fast.... the driver.

Be prepared to be slow and make lots of mistakes while learning to do things like trail brake or left foot brake. It takes practice.

I should have clarified that I was speaking of rear engined Porsches. I know little about front engined cars and their inheritant characteristics. I did notice that you referenced a 911 with an LSD, have you tried going deep in a 911 without a diff?

I have a 911 with a clutch-type LSD and another 911 with just the open diff. It is very difficult to trail brake with the open diff, but it is possible.
If I do a decent job at it (i.e., really smooth wih the brakes and wheel), it does allow me to brake later/deeper. There is more forgiveness with LSD.

Another benefit of trail braking is that it often helps settle the car during the transition from straight to corner (depending on the particular corner).

Neither of my track 911s has ABS, which changes the situation totally, of course ( a LOT more forgiveness).