Left foot braking vsCorner Brake Control

[Spookyfish]

Quote: Originally Posted by nonsequitur

I now use left foot braking much more on the street, and it's the preferred method in the Cooper CVT for track days. I'm getting better but when I think I'm getting good, it's time to take a driving class to restore the absolute knowledge that there is a LOT TO LEARN.

Here is an amazing video clip of Walter Rorhl dancing in the Audi Quattro, with a focus on his footwork and left foot braking. Enjoy a lesson from the master!

Walter Rorhl/Audi Quattro

WOW! I do keep wondering how his footwork is related to the adjecent piece of road in the film...

[nonsequitur]

I doubt that there is any single piece of the streaming video from in the footwell that directly connects with the footage out the windscreen, but to watch all of this going on is flat AMAZING.

Watch his right foot. You're seeing downshifts (matching revs), upshifts, and throttle steering (managing oversteer/understeer to rotate the car and power through those corners).

Left foot braking is employed to slow the car, or to balance the car in corners (transfering weight forward to rotate, etc).

Any time someone says that driving in low coefficient conditions is easy, this is a clip to recall as you say "Ya, sure!"

[obehave]

Excellent video

[jlm]

very cool; makes me feel even more oafish

[Gas O]

Fine choice in footwear as well ...

[Cooper76]

Quote: Originally Posted by Gas O

Fine choice in footwear as well ...

You mean I should switch out of my 10-holed, steel-capped Docs when trying this for best results? Doesn't Jenson Boyo wear these whilst motoring?!?! (Go You Williams!)

Heeheehee...

[Penguinracer]

Guys,
Walter is one of the greatest & was voted Driver of the Millenium by his peers who span the top league of FIA motorsport - Formula One & WRC. That footage is taken from the 1986 San Remo Rally in the quattro E2 - the last victory for what I feel is the most charismatic rally car built. Some of the outside shots show a quattro A2 (LWB) and others show an E1 and an E2 - so there is a mismatch between the interior shots and some of the exterior shots.
Walter came to left foot braking relatively late in his career. In his book "The Walter Rohrl Diary" (thoroughly recommended) he says that he only learnt about left-foot braking when he went to Audi & he couldn't qwell the quattro's understeer. Stig Blomquist (the left-foot master!) took him out in a recce quattro & demonstrated the technique. Walt claims that it took him quite a while to refine it because he kept changing the pressure on the brake pedal while he pumped the gas. He learnt that the secret is to retain a constant pressure on the brake pedal while varying the throttle. Ever the modest Finn, Blomquist denies that he taught Walter the technique & says he picked it up himself. I know I may sound like an anorak (geek), but much as I love the Mini I lalso have two Ur-quattros (early & late) because like many petrol-heads in their 30's & 40's I was heavily influenced by the Group B era of rallying which I humbly submit was a short but golden era in motorsport.

I think with all the talk of Formula One drivers, guys like Walter Rohrl don't get as much public recognition as they deserve. It's a great video though.

[nonsequitur]

Quote: Originally Posted by Penguinracer

Walter claims that it took him quite a while to refine it because he kept changing the pressure on the brake pedal while he pumped the gas. He learnt that the secret is to retain a constant pressure on the brake pedal while varying the throttle.

A wonderful Post that you put up here. Thank you for the confirmation, and the new information to think about. I simply agree with you about Walter Rohrl.

In the CVT-equipped cars, I'm finding the opposite situation may be necessary (steady throttle, modulated brake) in SD because of e-throttle, the EMS2000 computer and MINI software. We must find ways to quiet throttle inputs if driving in D or SD so that the computer issues logical commands for forward progress.

This is not the case in Steptronic with it's very strong Manual characteristics. I was toying with it this past weekend on PIR (Portland). Decisive throttle movement clearly rotates the car! I've got a long ways to go...

[phoggberg]

I am having a little problem with this post... to be honest nonsequitur and I have been having this discussion off-line, and I yet don't have a MINI to find out for sure, but in reading all my specs very carefully (you all probably did that while waiting for your cars to be born) The electronic brake balancing control, which the literature says can't be turned off, will not allow the technique to be used. That doesn't say some application of braking won't help cornering, but that is because of weight transfer at the turn in point. LFB is premised on the fact of locking up the rear wheels, while keeping power applied to the front wheels, and keeping them turning. Not only does this cause a weight shift, but it makes the rear wheels lose adhesion, and causes over steer. You can get the same effect in a gross manner by applying the handbrake rapidly, and hard. This causes the rear end to essentially break loose, and the car will pivot about its center of gravity in a very sharp turn (easy to make a 180). LFB does the same thing but with more finesse giving you better control. Perhaps with practice, you can do right hand breaking, and cause the same effect. Read the link again, it clearly states that the rear wheels have to lock up in order for effective LFB to happen, but the MINI won't allow that to happen, according to my reading at least. Hopefully soon in an icy parking lot or frozen lake I will know for sure.

When you apply braking that forces a weight shift to cause the nose to dive at the turn in, you tires become more effective, and the increased grip pulls the car tighter into the turn. This however is short lived, and ceases to have a major effect as centripetal force near the apex begins to make a FWD car over steer. Using full LFB you actually skid the car around the turn by keeping the car in an over steer condition, which can last from entry in the turn until acceleration out of the turn causes enough weight shift for the rear wheels to regain adhesion and kills the over steer, allowing you to drive out of the condition.

Use of momentum and inertial alone is more in the realm of the Swedish flick (named in honor of the Swedish WRC teams(s) who originated the technique) which I have never had the guts to master -- I am always afraid of putting the car on the roof, though I doubt that would happen -- well you know what they say -- No Guts! No Glory!

[nonsequitur]

Quote: Originally Posted by phoggberg

The electronic brake balancing control, which the literature says can't be turned off, will not allow the [LFB] technique to be used. That doesn't say some application of braking won't help cornering, but that is because of weight transfer at the turn in point. LFB is premised on the fact of locking up the rear wheels, while keeping power applied to the front wheels, and keeping them turning.

We're all lucky to have phoggberg joined in this debate. He brings huge experience and on-track success to our conversation about how to drive the MINI CVT. Let's listen carefully, and learn.

I fear that we have a conflict of "terms" versus actual technique in the car.

Left-Foot Braking (as I've been using the LFB term) absolutely does NOT require lock-up of the rear wheels. I'm saying "use your left foot to brake" versus "use your right foot to brake after transferring it from the gas pedal (the standard way to do it)."

Think of my comments in this light: I'm driving the MINI Cooper CVT like a kart: Left foot, brake; Right foot, gas; Hands, steering.

phoggberg describes a state of induced imbalance (rear wheels sliding) that is very useful in rallying or autocross, while I'm talking about balanced weight transfer front-to-rear (gas, or less brake) or rear-to-front (brake, or less gas) on road or track.

Another input choice would be on the autocross course, or that snow-covered parking lot this season!, to give sharp braking inputs through the hand brake to the rear wheels (with DSC turned off). This works too, but it would seem prudent only in situations where you needed gross movement (rotation of the car) such as a "spin cone" (180 degree turn) on an autocross course.

Here's a link earlier in this thread that does a good job of describing the balanced way I'm trying to use Left-Foot Braking:

Left Foot Braking

Smoothness is a critical condition at higher speeds on the road or track. I'd never want to consider using the hand brake at 80mph on pavement! To drive quickly through high speed corners, "balanced" grip makes it happen.

Let's get the terms worked out, and then re-engage the technique part?

[phoggberg]

Quote: Originally Posted by nonsequitur

We're all lucky to have phoggberg joined in this debate. He brings huge experience and on-track success to our conversation about how to drive the MINI CVT. Let's listen carefully, and learn.

I fear that we have a conflict of "terms" versus actual technique in the car.

Left-Foot Braking (as I've been using the LFB term) absolutely does NOT require lock-up of the rear wheels. I'm saying "use your left foot to brake" versus "use your right foot to brake after transferring it from the gas pedal (the standard way to do it)."

Think of my comments in this light: I'm driving the MINI Cooper CVT like a kart: Left foot, brake; Right foot, gas; Hands, steering.

phoggberg describes a state of induced imbalance (rear wheels sliding) that is very useful in rallying or autocross, while I'm talking about balanced weight transfer front-to-rear (gas, or less brake) or rear-to-front (brake, or less gas) on road or track.

I agree, and it is a terminology problem we are having here. below is the relevant part of the link that nonseqitur provided.

One: The front wheels keep turning. And two: The rear wheels try to lock up. If you are in a turn, the back of the car will start to slide toward the outside of the turn. To control or stop the slide, apply less brake and more power ( this changes the over steer toward understeer and stops the rear wheels from sliding toward the outside of the turn ).

I agree that the technique starts similarly, but the end result is different. Left Foot Braking is putting the car into a controlled imbalance condition. What nonsequitur is describing is more aptly described as weight shift control.

I don't think you can do LFB as I mean it in the MINI, except using the hand brake, and that will require a deft touch, but it is possible -- I think I will try to learn.

With DSC off though the Swedish Flick might be a technique that can be cultivated. There you turn the car (somewhat sharply) in the opposite direction from the intended turn, and then swing the wheel into the turn at the turn in point. This caused the cars inertia to move to the outside of the turn, and the rapidly towards the apex, causing the rear end to break loose, causing a much tighter turn. Usually done on gravel or ice/snow I am not sure its used in hard surface racing, but is popular in the WRC

[nonsequitur]

Quote: Originally Posted by phoggberg

I agree that the technique starts similarly, but the end result is different. Left Foot Braking is putting the car into a controlled imbalance condition. What nonsequitur is describing is more aptly described as weight shift control.

I'll just accept this as true, but I don't see a difference between what I'm describing and the article on Left-Foot Braking linked in the earlier post. It clearly talks about using the left foot, and the intent is balance, adjustment, and very controlled rotation of the car.

It's important to say the tires are sliding (slip angle) all the time in a corner. The degree of slip angle difference between the fronts and rears can be managed short of losing grip (break away) by inputs of steering, throttle, and brake. The MINI permits both throttle and brake to be used at the same time (good), and the way to do that in the CVT-equipped MINI is with your left foot on the brake and your right foot on the gas.

I think we agree, except on the amplitude of the result.

WRC and SCCA rally massively slide the rear to rotate the cars around slow, tight corners. They are probably using LFB, and many times a touch of hand brake (using that repositioned and lengthened handle next to the steering wheel). The objective is lock-up and break away of the rears, just as you say.

The same technique, but much less aggressive, is useful on the road and hard surface track to help rotate the car in more sweeping corners at much higher speeds. Lock-up and break away of the rears would be a disaster (a big spin).

My focus in all of these threads has been on road (or track) techniques, not rally. It is not necessary, and not desirable, to have the rear "step out" abruptly in a high speed corner on a road course. Smoothness counts for everything. LFB permits bias to be applied to the MINI, in a corner, for enhanced control not loss of control.

It works!

[phoggberg]

Quote: Originally Posted by nonsequitur

It's important to say the tires are sliding (slip angle) all the time in a corner. The degree of slip angle difference between the fronts and rears can be managed short of losing grip (break away) by inputs of steering, throttle, and brake. I think we agree, except on the amplitude of the result.

Agreed, and usually as you describe the focus on the road courses vs a rally stage. Although rally stages implement the full range of pavement conditions. From 180 degree hairpins in a forrest bog (especially after the Open Class hotshoes have really ripped up the road surface before you} to 140 MPH sweepers on tarmac mountain roads, and so employ a broad range of driving techniques. I don't even think we disagree on apmlitude, my focus is more towards rally and yours on a road circuit.

Quote: Originally Posted by nonsequitur

The MINI permits both throttle and brake to be used at the same time (good), and the way to do that in the CVT-equipped MINI is with your left foot on the brake and your right foot on the gas.

Well Heel and toe could be used but without a clutch why bother

Quote: Originally Posted by nonsequitur

WRC and SCCA rally massively slide the rear to rotate the cars around slow, tight corners. They are probably using LFB, and many times a touch of hand brake (using that repositioned and lengthened handle next to the steering wheel). The objective is lock-up and break away of the rears, just as you say.

The same technique, but much less aggressive, is useful on the road and hard surface track to help rotate the car in more sweeping corners at much higher speeds. Lock-up and break away of the rears would be a disaster (a big spin).

Not always a big spin, its a matter of degree of application a little lockup and small slide works too.

As a word of caution these techniques are not recommended for the public highways, but only in a controlled environment of a closed course. So for those learning technique but not yet applying them to competiotion, (that is driving hot on the public roadways -- the techniques we are discussing here are way to extreme for the public roads with civilian traffic around every corner) That does not mean you can not aplly the basic principles we are talking about on that curvey section of public highway, just do it at a reasonable speed. For example, instead of heavy left foot braking causing a slide, use weight transfer to change the handling from slight understeer to slight oversteer.

For the novices try this experiment...
Find a cloverleaf turn, or some constant radius curve. When reaching a speed in the turn that you feel the centripital force pulling at you, lift sharply off the gas, and you will feel the car tighten into the turn for a brief instant without changing the steering wheel. This is weight shift induced oversteer. If you apply some throttle, you feel the car tend to steer to the outside of the turn (understeer), again without changing the steering inputs. A tap of the brake the car turns in, a blip of the throttle the radius widens. It is an exercize in finesse. After getting comfortable with constant radius, look for some decreasing radius and increasing radius turns and use throttle an brake to tighten/widen the turn rather than steering inputs. Then progressing to off camber, and rogh surface (where bump steer comes into play) work up slowly both in speed and complexity. When you find yourself at either twice recommended posted speed, or more than somewhat over the speed limit, it is best to stop, and find a closed course to play on.

And out by where nonsequitur is are there are some wondrful roads around Olympia to play in

Quote: Originally Posted by nonsequitur

It works!

yes it does!!!

[nonsequitur]

Well, how about that for cooperative posts to sort out a situation! That was fun. I liked the disclaimer about public roads too. Do we now need to be centered back on a particular question?

[squid]

Last year I hired Robert Carpenter (through Evolution autocross school)
to demonstrate. He used LFB entering turns, and the transition from
lifting off th gas to deep into the brakes to coasting to back on the power
was very smoother.

My conclusion: LFB works with alphabet brakes.