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Trail Braking


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#1 PhantomEagle

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Posted Aug 09 2016 - 06:04 PM

I have been playing games like Gran Turismo 4 and even Enthusia for the PS2 over the past years, thing is, it always bugged me if Trail Braking is supposed to basically keep your grip at 100% during the turn or it's something mandatory to use the car at it's fullest potential.

I mean, there was a License Test in GT4, IB (International B) license to be exact, where you had two tests that detailed Trail Braking, the first one had you driving a Hyundai in the Tsukuba Circuit, the test taking place in Turn 1.

Then there was the second test that had you driving a Mercedes in the Green Hell, taking place somewhere like... let's say in a very late part of the track, can't remember the number of the turn where the test took place in, sorry.

Got gold on them after practicing.

Thing is, what is the real purpose of the Trail Braking Technique? Do you have to use it all the time or on very specific contexts?

Is it necesary to outpace the driver behind you or it should be used only in Qualifying sessions?

I mean, that Trail Braking technique came to mind when i got 1:23.xx on Kyalami with the Lotus on the '69 car set (Original Car Set), so, thought of asking if other people should consider using that technique if they want to improve lap times like me.

Hope someone can tell us what Trail Braking is really supposed to do, everyone else would appreciate to get some help about learning the purpose and even the origins of this technique.

#2 SV3000

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Posted Aug 09 2016 - 10:25 PM

Hey there, from what I read you already have the answer in your post.
Trail Braking is one of the most important way to improve lap time, and delay braking point which gives a huge advantage in battle. It's one of the thing you just have to learn and do at certain point when nothing else can improve your time further.
From my online racing experience, in high level competition and top class race, people almost always use it (just like any other regular driving technique, its not a special thing after all), it's the kind advantage that no one would like to give it up.
Just my opinion, hope helps.

#3 Andy Clegg

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Posted Aug 10 2016 - 01:13 AM

"Trail braking only gives you a lap time advantage if you are able to brake later than with the traditional style". This quote is from "Driving on the Edge" by Michael Krumm. An excellent read. All sorts of hints and tips to drive faster.

#4 Fat Rich

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Posted Aug 10 2016 - 04:30 AM

Trail braking is super important in modern sims and modern racing cars as they have so much grip. If you want to be fast in Assetto Corsa, Autosnowmobilista, rFactor2, Raceroom etc. you'll have to do it for almost all of the cars.

In GPL it very much depends on your driving style and your differential setup.....

I use "easy" diff settings (as found in most GPL default setups) and use quite a lot of trail braking in medium and slow corners to get some weight transfer onto the front wheels and give much more grip on turn in. Actually to the point of inducing mild oversteer and sliding the car into the corners to scrub of some speed if necessary, great fun :). Also if I out-brake someone on the inside I'll generally trail the brakes a tiny bit but very deep into the corner to help keep my car at the apex and not slide wide and collide with the other car.

Some other people use "fast" diff settings (as found in 69 mod default settings I think) and seem to use brakes and gas at the same time to stop the car spinning on corner entry, a whole world of weird that I don't understand :idunno:. They seem to only be using the power side of the diff and never using the coast side, very odd but it seems to be faster. It takes a level of skill and fast reactions that I just don't have, plus I just don't enjoy GPL when the cars feel so unstable :dontgetit:

In real life however, one of the reasons Jim Clark was so fast was because he trail braked more than most of the other drivers: http://www.motorspor...m-clark-457812/

Edited by Fat Rich, Aug 10 2016 - 04:33 AM.


#5 isamu

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Posted Aug 10 2016 - 06:56 AM

when using it in GPL, does it help you perform and hold slides longer?

#6 Fat Rich

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Posted Aug 10 2016 - 08:06 AM

View Postisamu, on Aug 10 2016 - 06:56 AM, said:

when using it in GPL, does it help you perform and hold slides longer?

The way I drive it helps me get the car a little sideways on corner entry but I wouldn't say it helps to hold slides longer. That's more about getting the right amount of throttle to transfer the car's weight back to the rear wheels and get just enough grip to hold the slide. To much throttle and it'll make the slide worse by spinning up the rear tyres.

But I guess it depends how you set up the car, I run mine fairly soft with very low rebound settings front and rear which makes slides happen slow enough for my rubbish reaction times..... but I'm a couple of seconds off alien times :(

Still, I'm having fun and that's the main thing for me :D

Edited by Fat Rich, Aug 10 2016 - 08:08 AM.


#7 Fat Rich

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Posted Aug 10 2016 - 08:10 AM

Forgot to add, the brake bias settings in the default settings are way too far forward for my driving style (very smooth) to trail brake nicely, I generally end up around 52% to 53% on most cars.

Edited by Fat Rich, Aug 10 2016 - 08:10 AM.


#8 Pete Gaimari

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Posted Aug 10 2016 - 09:39 AM

Yes, I trail brake in almost every turn. It lets me brake much later and that important with the AI as they brake late. If you didn't trail brake you'd have to get all the braking done while you're still going straight. That's too slow and will hurt your lap times. You'll also get passed by everybody who trail brakes. I don't use it to turn the car on turn entry. I have the car setup to turn on it's own. I don't like to slide the car.  Maybe a bit coming off the turns with power, but never going into a turn.

I agree that Jim Clark was fast and one of the first driver to trail brake. I watched him in 67 at Watkins and it was obvious he was braking later than the other drivers.

#9 John Woods

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Posted Aug 10 2016 - 12:15 PM

Sliding/drifting slows the car, so do it the least possible whether trail braking or just having fun.

My preference is to use a very quick little drift to change the direction of the car just after minimum slowdown at entry. With a little drift it is possible to come into the turn a little faster with less or no braking.

Use diff coast to turn car. Put car into coast by relieving throttle slightly after minimum slowdown, then trail brake just enough to set car up for acceleration on thru the turn. "Set the car up" means balance the car so the slip angles on all four tires are the same. It all happens at once as part of turn in.
Get back on throttle smoothly and accelerate while maintaining slip angle balance using throttle and steering input.

Grand Prix Legends tracks generally have a surface rise on outside at entry. Use the rise to assist brakes in slowing the car. From then on its power on.

Recently watched a video of various cars going thru Canada Corner at Road America. There were two groups of cars and each took a different line.

First thru were some sort of probably high power mid-engine cars that came in very fast with what appeared to be heavy trail braking on entry. They all took the same line, slowing very deep into the corner, tight on the inside, with a very late apex. It looked like they were almost coming to a stop, then they would blast off into Thunder Valley as if on a drag strip.

The next group of cars were an assembly of vintage front engine sports cars, no doubt with much less power. They all slowed in a straight line before entry, turned in early, and accelerated thru an apex well away from the inside of the corner. They were obviously, (to me), trying to maintain a higher average speed thru the turn.

So just my guess, the more power available to quickly get the car back up to speed, the less necessary it is to get back on throttle before an early apex and the more advantageous it is to trail brake. With less power, any braking, sliding, or drifting, will result in slower lap times.

All of the above is questions and guesses...

Edited by John Woods, Aug 10 2016 - 12:25 PM.


#10 JonnyA

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Posted Aug 10 2016 - 12:16 PM

I trail brake pretty much all the time, certainly in slow and medium corners. You can brake very late but you must carry very light braking (maybe just 10% of maximum) almost right up to the apex. I like to get the car sliding before I come off the brakes, so I have a slight slip angle for maximum grip, and also if the car is already sliding I find it easier to provoke gentle wheel spin when I get back on the throttle, for maximum acceleration.

In fast corners I dab the brakes early to provoke a drift and then play with the throttle and steering angle to adjust my speed and line through the corner. Not sure if that still counts as trail braking, but I do brake as I 'turn in'.

#11 JonnyA

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Posted Aug 10 2016 - 01:49 PM

I've just been for a walk, during which I was thinking about trail braking. Funny what GPL does to you. Anyway, I think an ideal data trace for me while trail braking would look something like this:

Posted Image
Red = Braking effort
Blue = Steering effort
Green = Amount car turns

The 'Oh ::crap::' zone is the period during which the car feels like it is on a ballistic trajectory and you have no real control over it. This lasts until the car has slowed enough to respond to steering efforts other than trying to keep it in a straight line. If it doesn't feel like I have left the braking too late, I'm not trying hard enough.

You can see that I brake, gently, all the way up to the point at which I re-apply throttle, which is at the very right hand end of the graph. But before then I have centralised the wheel and am steering just with the brakes to get to the apex.

#12 maddog

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Posted Aug 11 2016 - 07:19 AM

View PostPhantomEagle, on Aug 09 2016 - 06:04 PM, said:

Hope someone can tell us what Trail Braking is really supposed to do, everyone else would appreciate to get some help about learning the purpose and even the origins of this technique.
Trail braking has been used, for as long as tyre design has made it an advantage.  Good drivers would have discovered, and continue to discover it's use, almost instinctively.  How much of an advantage it gives, has always been a matter of driver skill.  In our Sim, it takes a long time to become an expert, and learning it's technique is an important part of the process, towards greatness.

The problem for many, hoping to become G_P_L experts, is having no real World experience in driving high performance rear wheel drive machinery, made for the track.  All road going RWD's for the family, come with low speed understeer built in.  And Front WD's characteristics are quite different - in my experience they love to plow, and put a furrow in the brow. :really:

Understeer is made not for maximum performance, but for maximum safety.  Safety for Manufacturers as well as for average drivers.  Lawsuits are less when the car does not turn itself towards the crash!  A good driver would take better care, and corrective action.

So why trail braking?  I've a simple answer :

Approaching a corner, you want maximum tyre performance, spread over the maximum time of cornering possible.  Trail braking starts the corner early.

#13 bobzdar

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Posted Aug 13 2016 - 08:37 PM

This article explains the why very well, but in short there's an ideal amount of latitudinal and longitudinal acceleration for a given car/corner combination, and a tire has a finite amount of grip that you can use.  The power/weight ratio plays a big part, along with how much traction you have along with how tight the corner is.

http://www.winnersbi...0-687584751.pdf

In short, a lower power/weight car wants a more even turn (ie brake straight line, turn through, accelerate) where a higher power/weight car wants it more skewed (turning in earlier, harder turn at the center, on the accelerator earlier with a shallow exit).  As the GPL cars have a high power/weight and low grip, they perform well with more skewed cornering, and if you don't trail brake you won't be using all of the available grip the tire has.

#14 maddog

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Posted Aug 14 2016 - 10:04 AM

"As the driver corners, increasing lateral acceleration, the available longitudinal ACCELERATION falls :  high acceleration while turning too sharply causes a skid."

Some interesting ideas Bob.  I read part of the article, which seems to be written without full understanding of scientific terminology.  As it deals with the Science of cornering, this seems a bit odd. :huh:

Certainly inspirational for all those wanting onboard telemetry, and an engineer who understands how to interpret it into action.  But the article blends corner braking and acceleration, which will cause some confusion.


Power to weight and trail braking :

Jochen Rindt F2 Thruxton - total mastery of rear out trail braking.  Less power to weight than an F1.  Jody Scheckter FFord Brands Hatch - full opposite lock trail braking. ( Last lap only, but some every lap )  Little mid 60's Mini Coopers, trail braking rear out, into every corner in clouds of blue smoke! ( get some here : http://srmz.net/inde...?showtopic=9238 )

Power to weight affects acceleration, and not deceleration.


The goal of engineers is to replace the art of driving with pure Science.  They have yet to succeed. :P

#15 bobzdar

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Posted Aug 14 2016 - 11:48 AM

Yes, all cars benefit but the higher the power/ grip (not necessarily power/ weight as aero makes a big difference) the higher the degree of trail braking needed to achieve the ideal line for optimal corner exit. As the gpl cars have some of the highest power/ grip of anything you'll drive, they need a much less circular and more parabolic corner line to get ideal corner exit, which necessitates more trail braking to maximize use of available grip on that line.

Or something like that.

That article appears to be a synopsis of a longer one I read 15 years ago or so, but I couldn't find it :(

#16 John Woods

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Posted Aug 14 2016 - 12:10 PM

"Trail braking" search on Bing = 8.33 million hits.
:)

Three versions of why, what, when, and how...

http://driver61.com/uni/trail-braking

http://www.racingont.../trail-braking/

http://http://www.ph...nfo/phors23.htm

Trail braking is using brakes, throttle, and steering at the same time?
Maybe doing it more in F1 had something to do with engineers getting the steering column out of the way?

#17 David Wright Lo67

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Posted Aug 14 2016 - 01:53 PM

View PostJohn Woods, on Aug 14 2016 - 12:10 PM, said:

"Trail braking" search on Bing = 8.33 million hits.
:)

Three versions of why, what, when, and how...

http://driver61.com/uni/trail-braking

http://www.racingont.../trail-braking/

http://http://www.ph...nfo/phors23.htm

Trail braking is using brakes, throttle, and steering at the same time?
Maybe doing it more in F1 had something to do with engineers getting the steering column out of the way?

Just the brakes and steering.  The position of the steering column has no influence.

#18 John Woods

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Posted Aug 14 2016 - 02:31 PM

This is from the Racing on the Cheap page, (2nd link in my last post),

"With further practice you can use trail braking with your left foot in medium-speed corners while continuing to use the right foot to cover the accelerator. Then once you finish braking, move to neutral throttle, and then to progressive acceleration just before the apex. Neutral (or balanced) throttle is when the driver feathers or covers the throttle, applying just enough power to keep the car at a constant speed, not accelerating nor decelerating."

Above description is confusing to me, so just wondering about it.
Not possible when steering column is between left foot and brake pedal.

Race engineers use science to try and explain what the heck it is drivers are doing?

Little later edit:
Now thinking the above description covers two distinct operations.
The first is trail braking with brakes and steering to get into turn farther and faster, saving time.
The second operation, introducing throttle, is to balance the car for acceleration thru a turn.
Ideally, jmo, a well prepared car will settle into asymmetric (off-center) neutral balance on its own without a lot of complex driver input.

Edited by John Woods, Aug 14 2016 - 06:56 PM.


#19 Andy Clegg

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Posted Aug 15 2016 - 09:10 AM

"Use your normal braking point, not braking as hard. Your'e arriving too fast where you turn in normally, (release brakes now and car will understeer). Keep your foot on the brake, but release pressure just before turning in. Turn in slowly with the brakes still on and drive towards the apex".

#20 Pete Gaimari

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Posted Aug 15 2016 - 10:38 AM

John........Trail braking is not using the throttle with braking. What you quoted is wrong.

Trail braking is applying the brakes and releasing pressure on the brakes as you approach the apex. You are trailing off the brakes. Which is how it got the name.

Using throttle with braking is a rally technique. Which really abuses the car. Not sure it has a name.

I remember when Massa went to Ferrari he was using the throttle while braking and Ferrari told him to stop it.




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