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scars_of_carma
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PostSubject: Using Brakes   Wed Oct 28, 2009 12:06 pm

What happens when you step on the brake pedal? LOTS of things happen but the specifics don't matter. As the driver all you are concerned with is feel and control. I'll say it again, feel and control.

I could tell you the entire chain of events that happens so your foot can stop the tires but it'd probably literally take pages... so lets just concentrate on the byproducts of braking. Namely; Bite, Traction, Slip, Fade and weight-transfer.

The initial feel of the brakes is what I call bite. Bite is good. Good brakes have bite. Barqs Rootbear also has bite... Bite means you get to apply maximum braking instantly but more importantly bite = feel. If you can feel when the brakes engage and how hard they engage you can better modulate the brakes (or just use ABS) to keep them at their threshold where they do the most work.

The grip of the tires is obviously Traction. Traction is good. Good tires have traction. Traction means you can actually use your good brakes with bite but more importantly traction = control.

Loss of traction is what I call slip. Slip can be good but only when you want to slip. Slip is mostly bad. Slip is bad for traction and slip ruins bite. Slip = loss of control.

Fade is loss of friction. Loss of friction is bad. Your brakes (and your tires) depend on friction to function. Bite in your brakes (or tires) can cause fade if they are sucky brakes. Fade means you no longer feel whats happening. Fade = loss of feel.

Weight-Transfer is the result of g-loading. Sharp steering, hard braking or hard throttle cause weight-transfer. This isn't a bad thing. Weight-transfer can improve traction and control when used properly.

Now back on topic. You are likely to understeer if you initiate braking after turn-in.

However when you initiate braking before turn-in (like you're supposed too) the weight-transfer of braking puts more load on the front tires which also momentarily increases their traction. As you turn-in smoothly you ease off the brakes smoothly. The trick is to use that extra traction from the forward weight-transfer at turn-in when you need it most!

Sounds simple enough doesn't it? Now for some advanced techniques based on that principle...

Super-late-braking is basically waiting to initiate that weight-transfer for turn-in at the last possible second. That way you don't waste any speed approaching the corner. On a racetrack this is the most common means to overtake. This technique requires good bite in the brakes, mastery of threshold braking and good traction in the tires.

Trail-braking means you don't release the brakes completely until you reach the apex (roughly the middle) of the corner where you start to accelerate out of the turn. The advantage of this technique (and also the risk) is that you can brake deeper into the corner. This technique is the most difficult because it requires the most control and excellent judgement of your entry speed. You also need excellent traction and brakes that do not fade!

When you use trail-braking, you are basically controlling the foward and lateral weight-transfer like a balancing act. In addition to maintaining constant forward g-load you need to maintain constant lateral g-load as well.

Basically the reason for this is balance. Race drivers (especially circle-track guys) try and maintain constant loading of the tires via brakes, steering and throttle through a corner. If your judgement is off you spin or worse understeer up into the wall...

Think of it like this, the whole of the forward g-load (brakes) and the whole of the lateral g-load (steering) must not exceed the limit. In other words, the limit of traction cannot be multiplied. It can only be divided.

Thus, when you are entering, holding, and leaving a corner you can't stack the loads on top of eachother and expect a higher limit. You have to redistribute the loads as you are going through a corner or you will exceed the limit.

To reiterate you brake until you hit the limit of your traction before turn-in. Then you smoothly release the brakes adding steering to keep your tires loaded all the way to the apex where your lateral-g's are the highest. Then you smoothly apply throttle as you unwind the wheel to achieve the highest possible exit speed. It requires feel and control to do all these things fluidly.
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Z Infidel
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PostSubject: Re: Using Brakes   Wed Oct 28, 2009 12:45 pm

No comment on brake lift as it effects weight transfer? (just constructive criticism)
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specVance
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PostSubject: Re: Using Brakes   Wed Oct 28, 2009 12:50 pm

"Barqs Rootbear also has bite..." hahaha

Good post man.
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scars_of_carma
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PostSubject: Re: Using Brakes   Wed Oct 28, 2009 1:14 pm

Z Infidel wrote:
No comment on brake lift as it effects weight transfer? (just constructive criticism)

You're right that it is an important point...

Be as careful releasing the brakes as you are using the brakes. Weight transfer will occur either way.
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Z Infidel
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PostSubject: Re: Using Brakes   Wed Oct 28, 2009 2:26 pm

I only brought it up because at a recent auto-x it was a common issue causing spins.
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~The_Duke~
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PostSubject: Re: Using Brakes   Wed Oct 28, 2009 3:21 pm

Z Infidel wrote:
I only brought it up because at a recent auto-x it was a common issue causing spins.

Weight transfer is an important parting of handling wither it be caused by the brakes or getting on the gas or the lack of either one.

Depending how your car handles and how it reacts to weight transfer, left foot braking can be VERY useful in maintaining proper balance around a corner.

There is a reason why it is says "balance is key" on the back of the 4touge hats.
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Z Infidel
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PostSubject: Re: Using Brakes   Wed Oct 28, 2009 3:26 pm

I used to be so good a left foot braking....sigh
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specVance
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PostSubject: Re: Using Brakes   Wed Oct 28, 2009 3:43 pm

~The_Duke~ wrote:

There is a reason why it is says "balance is key" on the back of the 4touge hats.

haha yes
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~The_Duke~
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PostSubject: Re: Using Brakes   Wed Oct 28, 2009 3:51 pm

Z Infidel wrote:
I used to be so good a left foot braking....sigh

I still cant do it right, but I know how and when to use it; However... my left foot is retarded, and only works correctly on the clutch.

I need practice and seat time to master this.
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bomjoon
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PostSubject: Re: Using Brakes   Wed Oct 28, 2009 8:09 pm

too long ... did not listen. Razz
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Z Infidel
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PostSubject: Re: Using Brakes   Wed Oct 28, 2009 8:12 pm

Zack, try using your toes instead of your whole foot. It takes a bit of muscle memory but you should get it soon.
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~The_Duke~
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PostSubject: Re: Using Brakes   Wed Oct 28, 2009 8:28 pm

Z Infidel wrote:
Zack, try using your toes instead of your whole foot. It takes a bit of muscle memory but you should get it soon.

The key is muscle memory, I just need to practice at it more.
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scars_of_carma
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PostSubject: Brakes and Tires   Wed Nov 11, 2009 10:57 pm

You should not initiate a turn before you start braking. You can continue to steer a little while you are trail braking if you have enough feel for control... Trail-braking will give the tires a little more slip angle to work with if you do it right.

A good driver can feel the limit of a tire at any given moment but that's only half of the challenge... . Improper setup makes the tires suffer and that will lessen traction in any circumstance. Alignment... tire grade... tire pressure...wheel bearings... etc... all these factor into braking performance.

I used to be a tire-monkey at Laguna Seca mounting slicks on race cars. You'd be surprised how many slightly-bent wheels are being run on any given race weekend. Ironic isn't it? Some guys buy a new set of slicks after every session but they don't have any spare wheels... You tell them their wheel is bent thinking you are doing them a favor and they just get this pissed off look like they'd rather have not known about it in the first place. ...Funny how fragile your self-confidence is as a driver when you doubt your equipment isn't it?

Anyways a good tire is only as good as its setup. If you have bent wheels or your allignment is whack 100% isn't going to feel that great. If you take the time to properly test your tires using depth-guages and probe-type pyrometers you can figure out how to make your tires happy. If your tires are happy your brakes are happy and you are happy.
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scars_of_carma
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PostSubject: Left Foot Braking   Wed Nov 11, 2009 11:02 pm

Ahhh Left-Foot-Braking... Yes that does require a bit of explanation. Earlier when I was talking about tapping the brakes...

[Quote=scars_of_carma]
...tapping the brakes. If you are ever in a situation where you are on the verge of understeer in a turn... braking or steering harder will just make it worse. Tap the brakes and continue to modulate the steering until you feel the grip come back into the steering. You might have to tap more then once... but just tap. This is the ONLY way you can safely use brakes mid corner if you lifted off the brakes after turn-in. [/quote]
...I should have mentioned that it is preferable to use your left foot. Under high-lateral-load you do not want to lift off the throttle if you can help it. You may oversteer or even spin if you lift off the throttle abruptly.

Now tapping the brakes aside lets talk about the other ways you can use LFB.

On Corner Entry: This is the trickiest time to use LFB becuase you also need to downshift. If you don't maintain load on the engine by matching the gears to the rate of deceleration your throttle response goes to s***. It is possible to LFB and still heal-toe but it requires very skilled footwork. It is also possible to downshift without using the clutch at all but that takes lots of practice. Finally I suppose this wouldn't matter at all if you were driving an automatic or had paddle-shifters.

While Trail Braking: This is the most advantageous condition for LFB. Just as with tapping the brakes the main advantage is you don't have to lift off the throttle. In fact because you are LFB you can release the brakes and apply throttle much smoother which, in theory, means you might be able to carry even more speed through the turn.

I have not LFB a FWD

Sorry at this point I can't personally give any examples of LFB in a FWD. Only rarely have I ever needed LFB to save my a** because I don't often drive fast enough to need it on sh***y public roads.

I did use it quite a bit on the track, while rallying, or doing auto-x because I competed with rotaries or other low-powered cars that rely on efficiency-of-momentum to maintain a quick pace. In other words the only way I could keep up was keeping the go pedal down as much as possible.
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MidnightblueMR2
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PostSubject: Re: Using Brakes   Thu May 10, 2012 1:16 am

You can also use LFB to perform a weight transfer shifting weight to the front end allowing you to oversteer or kill understeer.

I found LFB a game changer in a FWD car time it right with throttle, steering, and alignment setting you can four wheel drift a FF
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SPARTA
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PostSubject: Re: Using Brakes   Sun May 13, 2012 9:20 am

Good info

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JohnnyTsunami

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PostSubject: Re: Using Brakes   Tue May 15, 2012 1:37 am

I recently was asking scars about left foot braking... Lately I've been watching allot of rally videos and noticed that some guys use LFB religiously. And some don't use it at all.. Anyways so I asked him when the best time to use LFB would be.. And well he already answered above. He brought up the time we had to make a trip out of town in our roommates FC which has a really stiff suspension setup... as we were coming off the freeway to make a left turn, scars let off causing the rear to slip out.. we weren't going particularly fast for the turn.. . If he had known the car was going to react that way he said, using LFB while staying on the throttle could have prevented the rear end from slipping.
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~The_Duke~
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PostSubject: Re: Using Brakes   Tue May 15, 2012 7:30 am

As I have learned with my first RWD car and my first car that has a brake baisis valve on it. It all depends on how you have the car setup on when it may be useful.

My brake are about 55\45 front to rear. Just a guess, but the fronts will lock up a spilt second before the rears in the rain.

I dont need to use the LFB if you attack the corner and dont over do it coming out. However applying the brakes while coming out of the corner may help oversteer, on my car because of the setup make it switch to MASSIVE PLOW understeer. It goes away as soon as you lift off the brakes though so you can prevent from pulling a joey.

I think it would be best for me just to practice straight line braking, and if I find myself still to fast after entering so trail braking.

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MidnightblueMR2
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PostSubject: Re: Using Brakes   Tue May 15, 2012 9:18 am

You may be coming on too hard or too much with your braking.

So far I have used it for
my 240SX, Mr2, awd CRV, Maxima, and prelude.

The hardest thing about lfb is not mashing or stabbing at the pedal, which is what its used to
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~The_Duke~
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PostSubject: Re: Using Brakes   Tue May 15, 2012 12:00 pm

Nah it acutally does it no matter which foot you use.

I have a 11" rotors with a 4 pot caliper on there, the brakes are very touchy because they do have ALOT of bite. They arent really touchy until you start pushing them close to that lock up point.

If you just gave it alil bit of LFB coming out of a corner you would just have to adjust your steering abit once you lifted off the brake because the car would end up in a 4 wheel drift for a spilt second, but it will save you from spinning.

Most cars have a HUGE from brake biasis, you would be REALLY surpised how much different it feels after you tweak it to around 50\50. It stops you MUCH faster, but the car understeers badly under braking.


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bixs
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PostSubject: Re: Using Brakes   Tue May 15, 2012 12:48 pm

~The_Duke~ wrote:
Nah it acutally does it no matter which foot you use.
Most cars have a HUGE from brake biasis, you would be REALLY surpised how much different it feels after you tweak it to around 50\50. It stops you MUCH faster, but the car understeers badly under braking.

It's going to change based on the different size of the rotors/calipers from front/rear to find out how much bias you want for the car. Along with other factors (front/rear weight distribution). 50/50 for one car may be best because of the already present difference in braking forces from front/rear but could f* up another car.
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~The_Duke~
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PostSubject: Re: Using Brakes   Tue May 15, 2012 2:20 pm

bixs wrote:
~The_Duke~ wrote:
Nah it acutally does it no matter which foot you use.
Most cars have a HUGE from brake biasis, you would be REALLY surpised how much different it feels after you tweak it to around 50\50. It stops you MUCH faster, but the car understeers badly under braking.

It's going to change based on the different size of the rotors/calipers from front/rear to find out how much bias you want for the car. Along with other factors (front/rear weight distribution). 50/50 for one car may be best because of the already present difference in braking forces from front/rear but could f* up another car.

Exactly, and it depends on how you want it to feel with different tweaks of pad\rotor setups and tweaking the valve.
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MidnightblueMR2
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PostSubject: Re: Using Brakes   Tue May 15, 2012 9:55 pm

could you describe your corner entry technique?

on a 350ft radius turn with a arc length of 150ft.

Whats your entry speed, where do you brake, do you grip or drift, where do you start to rotate?

PS. I like to attack the road with my head. when you know the limit of what is possible you can go faster
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500KEG8
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PostSubject: Re: Using Brakes   Wed May 16, 2012 7:08 am

I only use LFB on relatively long sweepers, esp. one's I know well. It takes practice moving your foot over the clutch, esp. on a long right turns where I'm bracing my left leg against the door to keep myself in the seat! (but I just purchased a Sparco seat, it should remedy this!)
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~The_Duke~
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PostSubject: Re: Using Brakes   Wed May 16, 2012 7:13 am

I straight line brake before I enter the corner slowing to the speed at which I can take the corner at, and still have uh oh room, lifting off the brake just after my turn in letting the engine slow me alil more while switching to throttle. I heel\toe as well so I am at the lowest gear I can safely be in helping to keep the car stuck. With this car, the back end will be slightly out of line with the front. If it is a constatance radius, you should apex in the middle of the turn if there is a straight following. If there isnt a straight following, then you need to adjust your apex accordingly to setup up for the next turn.

I try to stay off the brakes as much as possible, if you are on the to much it will cause fading issues after a couple mins.

If I am autox'ing, I dont leave uh oh room because there are cones instead of cliffs and trees.
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