Left Foot Braking
Discussion
waremark said:
Unless the clutch is down or you are in neutral, lfb cannot help you keep revs higher than otherwise for your speed and gear. I am not clear whether having the throttle open have keep the turbo spinning although the revs will be no higher than normal. On the Pentti Airikkala case he claimed that this did work.
Just thinking through in my head - On a Diesel it probably wouldn't make any difference as you don't have a butterfly throttle and hence the volume of air through the engine would be constant (for a constant engine speed) for and given accelerator pedal position. However on a gasoline where there is a throttle, the air flow through the engine could be increased by pushing the accelerator so you get more air, more fuel, and hence higher energy exhaust flow, for the same engine speed, to increase/maintain turbine speed. However with all the fancy control on electronic throttles and turbo control, whether this would happen or not I'm not sure.
Edit: May happen on a Diesel too, the air flow rate is the same, but if you add more fuel you'll get greater expansion and more energy/mass flow down the exhaust too
Edited by IcedKiwi on Monday 21st September 09:38
Max_Torque said:
2) The different effect on dynamic stability because of where the decceleration forces are applied and how they are applied. When you brake, the longitudinal deccel force is reacted into the hubs at wheel centre height, and then reacted fairly evenly across the suspension components into the body shell. When you lift off, the deccel forces are reacted by the powertrain mounts, either resulting in lateral roll or longitudinal pitch moments, with a markedly different(negative) effect on weight transfer
This in particular applies to softly sprung FWD cars and is very noticeable when trying to get a heavy, wallowing saloon to turn in quickly without rolling on to its door mirrors by the exit of the corner. In a 3 pedal manual road car on the public road LFB can be useful in reducing body roll during a more spirited drive, but I feel only if conditions permit the corner exit gear being the same as the corner entry gear. You could of course clutchless shift on entry by blipping appropriately but your gearbox probably wouldn't enjoy the long life you'd prefer it to lead.
I have seen several 'hardcore' drivers LFB inappropriately, requiring a post-apex snap gear change and this is disadvantageous as a lack of drive and power availability significantly diminishes not only your control of a car mid-corner but also your exit speed. Such behaviour is contrary to the adage "Slow in, fast out" and on a public road, just dangerous. The exit of the corner generally is far more important than the entry of the corner as it takes longer to apply the speed than it does to lose it, so delaying power application on exit because you need to change gears just because of wanting to look big and clever by left foot braking on entry actually just makes you look like a tool.
Whilst still on the power at maximum speed, lightly applying the brakes with the left foot prior to primary braking with the right foot heats the brakes with very little impact on overall speed, meaning braking can be performed a touch later due to the heat generating more bite. This also allows for heel toe on entry and additional braking from the engine as well as being able to apply power earlier which, in a FWD car helps pull the car through the corner and thus minimises body roll somewhat. On exit one might then dab the brake with the left foot to bring a wheel under control as some have suggested, it depends on the situation.
Left foot braking in a 3 pedal car is all about knowing when and how to use it.
On a two pedal car I'd use it as default. At the moment we're looking for the next car & pedal arrangement that makes LFB easy is one of the criteria.
Currently I'm driving a AWD manual car (an old Forester XT) in an environment where a decent amount of my driving involves non-tarmacced roads. The grip on these roads depends not only on how dry / damp they are but also who's been using it recently. It can be very different at different parts of the road, so grip at the start of a bend can be different to the grip at exit or in the middle.
In these conditions, and occasionally on the road (in low grip situations) I tend to cover my brake with my left foot during cornering and use it to counter understeer if it arises. I feel that I can make small changes smoother & quicker using both feet than with one.
Currently I'm driving a AWD manual car (an old Forester XT) in an environment where a decent amount of my driving involves non-tarmacced roads. The grip on these roads depends not only on how dry / damp they are but also who's been using it recently. It can be very different at different parts of the road, so grip at the start of a bend can be different to the grip at exit or in the middle.
In these conditions, and occasionally on the road (in low grip situations) I tend to cover my brake with my left foot during cornering and use it to counter understeer if it arises. I feel that I can make small changes smoother & quicker using both feet than with one.
My apologies, this may be a bit of a lengthy post 
This strikes me as a decent summary of how experienced practitioners of LFB can use it for a genuine advantage -
For sure, in karting and some (typically higher) levels of racing where there are only two pedals a lot of drivers use both feet because they can and there are small benefits over having a redundant left foot but as an ARDS instructor I sit next to a lot of drivers on track and occasionally do get asked about LFB, in truth this is generally the correct answer -
, you would also need to have positioned the right foot correctly to allow correct heel and toe downshifts. Realistically, it's not going to happen.
This next part is slightly off topic but is another issue that is often misunderstood and goes to the OP's interest in the dynamics of the car -
For sure, braking towards an apex is a good technique in many cases but it is done for one (or both) of two specific reasons; first it may allow the braking zone to be started (slightly) closer to the corner, second (and much more importantly) it transfers weight to the front of the car making the steering more effective and allowing the driver a faster entry speed into the corner while still maintaining an ideal racing line.
So what's the problem with going straight off the brake and onto the throttle?
The thing to consider is that on a large proportion of corners, you can't brake all the way to the apex. Why not? Well, the corner simply may not be suited to it, if there is a long run from turn-in to apex you may just slow the car down too much, it may be a high speed corner where where the braking required is minimal anyway or where the high degree of weight transfer may have the adverse effect of causing excessive oversteer on entry, you may just have a lairy car that tends towards oversteer on turning that is made worse by trail braking.
Either way, if you are still on the entry phase of the corner and correctly maximising front grip to have a good line which will allow you to straighten the car past the apex (allowing maximum acceleration on exit), if you come off the brake and go straight onto the throttle you will transfer weight to the rear and lose that strong steering input. This will typically cause the car to understeer and run wide of the apex and even though you have managed to get on the throttle early, you end up having excessive amounts of steering to do past the apex and find yourself just tickling the power all the way out to the exit whereas staying off the throttle would have resulted in a good entry line, creating a wide exit and making room for a strong throttle application around the apex and a faster lap.
It's counterintuitive for a lot of drivers as blending throttle on the entry phase is a pretty normal road driver reaction and probably still correct for advanced driving (?, it's been 30 years since I did my advanced!) but my rule of thumb is that if you can get throttle on before the apex and still make the correct line, you went into the corner too slowly.
How does any of this apply to the dynamics of driving on the roads? Probably not much, I think there's a lot of wisdom in the posts that suggest that any dynamic gains achieved by LFB are inevitably going to be at traction limits which I would hope makes it irrelevant for any advanced driver in their normal road use and on the one time that you do start to run out of grip I'd suggest it may be a bad time to try a technique that at best has benefits when well practised and even then only under very specific situations.
Steve H
This strikes me as a decent summary of how experienced practitioners of LFB can use it for a genuine advantage -
R_U_LOCAL said:
Left-foot braking was developed by rally drivers in front-wheel drive cars as a way of controlling understeer, particularly in tighter corners, where there is a tendency for front-wheel (and many four-wheel) drive cars to push on under heavy throttle application on loose surfaces. Modern stability systems effectively do the same thing by quelling understeer through application of individual brakes.
Rally drivers also use left-foot braking as an additional - and instantly adjustable - method of changing a cars angle and attitude through a corner. So if they go into a corner a little too hot, the brakes can be applied to check the cars speed whilst balancing the weight transfer with an application of the throttle at the same time. The brakes can be used to reduce understeer and assist turn-in, or released to allow the car to exit quickly from the corner.
Where a front-wheel drive car has an open differential, it will have a tendency to spin up the unloaded wheel under heavy acceleration through tighter corners. Left-foot braking can counteract this tendency by bringing the spinning wheel under control and distributing the torque more evenly across the front axle.
But I'd have to disagree with most of this.Rally drivers also use left-foot braking as an additional - and instantly adjustable - method of changing a cars angle and attitude through a corner. So if they go into a corner a little too hot, the brakes can be applied to check the cars speed whilst balancing the weight transfer with an application of the throttle at the same time. The brakes can be used to reduce understeer and assist turn-in, or released to allow the car to exit quickly from the corner.
Where a front-wheel drive car has an open differential, it will have a tendency to spin up the unloaded wheel under heavy acceleration through tighter corners. Left-foot braking can counteract this tendency by bringing the spinning wheel under control and distributing the torque more evenly across the front axle.
R_U_LOCAL said:
Firstly, there is no delay in transitioning from accelerator to brake. This is particularly important in circuit racing where any time off the accelerator or brake could be considered wasted. Going immediately from full throttle to full brake application will result in a quicker lap time than lifting off the accelerator, moving your foot and then pressing the brake. It's a very small advantage, granted, but that's what makes the difference when it comes to lap times.
The delay between accelerating and braking caused by moving your foot across is truly minimal even in track terms when the braking is planned (which it typically is on circuit) and the majority of track drivers can make much bigger gains by judging the braking zones more accurately and not building an avoidable pause between the two pedals. For sure, in karting and some (typically higher) levels of racing where there are only two pedals a lot of drivers use both feet because they can and there are small benefits over having a redundant left foot but as an ARDS instructor I sit next to a lot of drivers on track and occasionally do get asked about LFB, in truth this is generally the correct answer -
annsxman said:
I reminded of a well known historic racing driver that I know who offers advanced tuition for would be gentleman racers. One asked him whether he should try left foot braking to which his response was that it would help if he could master right foot braking first! Apologies to the OP as I could see his was a serious question.
Aside from the marginal gains available, for most drivers you need to consider that if you are using LFB in any major braking zone - how are you going to change down the gears correctly? Assuming that you are in a manual car it would involve being able to slide your left foot off the brake pedal while moving the right on on there while maintaining threshold braking , you would also need to have positioned the right foot correctly to allow correct heel and toe downshifts. Realistically, it's not going to happen. This next part is slightly off topic but is another issue that is often misunderstood and goes to the OP's interest in the dynamics of the car -
R_U_LOCAL said:
Whilst we're on the circuit, Braking can be carried right up to a corners apex, with a smoother transition back on to the throttle away from the apex, rather than, again, there being a silght delay whilst coming off the brake and on to the throttle.
There are a few rules of driving on track such as "never put any power on unless you can keep it on" etc. Another one is "you should always be on the throttle or the brake", unfortunately this second one only applies to specific scenarios so while you do generally want to minimise the gap between power and braking at the end of a straight, you often will want a gap between braking and power as you go through a corner. For sure, braking towards an apex is a good technique in many cases but it is done for one (or both) of two specific reasons; first it may allow the braking zone to be started (slightly) closer to the corner, second (and much more importantly) it transfers weight to the front of the car making the steering more effective and allowing the driver a faster entry speed into the corner while still maintaining an ideal racing line.
So what's the problem with going straight off the brake and onto the throttle?
The thing to consider is that on a large proportion of corners, you can't brake all the way to the apex. Why not? Well, the corner simply may not be suited to it, if there is a long run from turn-in to apex you may just slow the car down too much, it may be a high speed corner where where the braking required is minimal anyway or where the high degree of weight transfer may have the adverse effect of causing excessive oversteer on entry, you may just have a lairy car that tends towards oversteer on turning that is made worse by trail braking.
Either way, if you are still on the entry phase of the corner and correctly maximising front grip to have a good line which will allow you to straighten the car past the apex (allowing maximum acceleration on exit), if you come off the brake and go straight onto the throttle you will transfer weight to the rear and lose that strong steering input. This will typically cause the car to understeer and run wide of the apex and even though you have managed to get on the throttle early, you end up having excessive amounts of steering to do past the apex and find yourself just tickling the power all the way out to the exit whereas staying off the throttle would have resulted in a good entry line, creating a wide exit and making room for a strong throttle application around the apex and a faster lap.
It's counterintuitive for a lot of drivers as blending throttle on the entry phase is a pretty normal road driver reaction and probably still correct for advanced driving (?, it's been 30 years since I did my advanced!) but my rule of thumb is that if you can get throttle on before the apex and still make the correct line, you went into the corner too slowly.
How does any of this apply to the dynamics of driving on the roads? Probably not much, I think there's a lot of wisdom in the posts that suggest that any dynamic gains achieved by LFB are inevitably going to be at traction limits which I would hope makes it irrelevant for any advanced driver in their normal road use and on the one time that you do start to run out of grip I'd suggest it may be a bad time to try a technique that at best has benefits when well practised and even then only under very specific situations.
Steve H
Let me add another 2 advantagea with LFBing modern cars:
1) You can control the wheel/tyre rotating inertia. Modern cars are powerful, grippy, but tend to have wheels / tyres (and brake discs / drive shafts etc) that have a relatively high inertia. If the drive wheels loose traction suddenly (like say when crossing a painted road line, or join in the tarmac) the high power of the engine, with no where to go, quickly spins up the wheel and tyre. This means it takes time for that wheel to slow down again when you (or more likely the DSC) reduce the engine torque (because positive torque is typically now 10 or 15 times more than negative torque, it spins up 15x faster than it slows down). By gently LFBing, i find that i can control the spin up, and not only prevent a more serious loss of traction, but get back on the power sooner by absorbing the excess power into the service brakes. This can also be particularly evident in heavily boosted cars with large intake manifold volumes, as these take a number of cycles to reduce flywheel torque even if the throttle is slammed shut immediately.
2) Pre charging the brake system by LFBing, with the brake pads pressing lightly against the discs means the DSC system has a much more subtle control of individual wheel speeds when acting as a traction control or dynamic stability manager. Instead of having to apply the individual wheel brake torque from fully retracted pads at zero pressure, it can start from a pre-loaded system. This makes a significant difference in both the phase delay and absolute response of the system.
1) You can control the wheel/tyre rotating inertia. Modern cars are powerful, grippy, but tend to have wheels / tyres (and brake discs / drive shafts etc) that have a relatively high inertia. If the drive wheels loose traction suddenly (like say when crossing a painted road line, or join in the tarmac) the high power of the engine, with no where to go, quickly spins up the wheel and tyre. This means it takes time for that wheel to slow down again when you (or more likely the DSC) reduce the engine torque (because positive torque is typically now 10 or 15 times more than negative torque, it spins up 15x faster than it slows down). By gently LFBing, i find that i can control the spin up, and not only prevent a more serious loss of traction, but get back on the power sooner by absorbing the excess power into the service brakes. This can also be particularly evident in heavily boosted cars with large intake manifold volumes, as these take a number of cycles to reduce flywheel torque even if the throttle is slammed shut immediately.
2) Pre charging the brake system by LFBing, with the brake pads pressing lightly against the discs means the DSC system has a much more subtle control of individual wheel speeds when acting as a traction control or dynamic stability manager. Instead of having to apply the individual wheel brake torque from fully retracted pads at zero pressure, it can start from a pre-loaded system. This makes a significant difference in both the phase delay and absolute response of the system.
Max_Torque said:
Let me add another 2 advantagea with LFBing modern cars:
...by gently LFBing, i find that i can control the spin up, and not only prevent a more serious loss of traction, but get back on the power sooner
Your boss appreciates these subtleties because they allow you to arrive at work earlier and leave later due to the commuting time saving. ...by gently LFBing, i find that i can control the spin up, and not only prevent a more serious loss of traction, but get back on the power sooner
R_U_LOCAL said:
Where a front-wheel drive car has an open differential, it will have a tendency to spin up the unloaded wheel under heavy acceleration through tighter corners. Left-foot braking can counteract this tendency by bringing the spinning wheel under control and distributing the torque more evenly across the front axle.
With an open diff the torque across both axles is always the same and that's the problem. a torque biasing diff transfers torque based on speed differential.With an open diff, braking allows more torque to be applied, therefore the wheel with grip gets more as well as the spinning wheel.
Edited by Gary C on Monday 7th December 14:36
Leftfoot braking was originally a technique used on Sabb v4 engines.
If you were driving your Saab uphill or on the level you spent most of your time on the throttle.When going down hill you would naturally come off the throttle,this created a problem!
These engines ran on a oil/petrol mixture and if you came off the throttle
down hill you would starve the engine of oil and it would seize!
The only way to overcome this would be to brake and stay on the throtle at the same time (left foot braking) to preserve the engine.
Of course then your brakes overheated
Saab didn't think this through!
This technique was used by 60's rally driver Eric Carllson who was married to Pat Moss,the sister of Sterling Moss.
If you were driving your Saab uphill or on the level you spent most of your time on the throttle.When going down hill you would naturally come off the throttle,this created a problem!
These engines ran on a oil/petrol mixture and if you came off the throttle
down hill you would starve the engine of oil and it would seize!
The only way to overcome this would be to brake and stay on the throtle at the same time (left foot braking) to preserve the engine.
Of course then your brakes overheated
Saab didn't think this through!
This technique was used by 60's rally driver Eric Carllson who was married to Pat Moss,the sister of Sterling Moss.
I am not sure that LFB originated on V4 Saabs. The earlier Saabs were 3 cylinder two strokes, and indeed they could easily seize on the overrun as there was very little oil being delivered to the engine when the revs were high. They overcame this by fitting a freewheel, so that the engine could revert to tickover revs when the foot was lifted off the throttle. This was continued on the V4 engined models.
I reckon that LFB was developed to cope with the vagaries of the 3 cylinder two stroke Saabs.
I reckon that LFB was developed to cope with the vagaries of the 3 cylinder two stroke Saabs.
In off-road situations with simple 4x4 chassis, left foot braking can be used to enhance traction when the limits of the chassis' compliance is reached. Typically, in a Landrover Defender, you can get it up some serious rocky slopes that would normally only be possible with more complex vehicles.
The LR's achilles heel is that it has a lockable diff only in the centre and no LSD. Therefore, when one wheel at each end is off the ground, as happens when diagonally opposite wheels leave the ground on very uneven rocky ground, the vehicle simply stops.
If you are in a sufficiently low gear to have plenty of spare torque left (to overcome the braking effect) then left foot braking will stop the two spinning wheels and see the vehicle regain grip and make progress.
Normally, only the very modern and expensive 4x4 vehicles have the ability to recover from that situation. With left foot braking in your 'toolbox', any cheap 4x4 suddenly becomes far more capable.
The LR's achilles heel is that it has a lockable diff only in the centre and no LSD. Therefore, when one wheel at each end is off the ground, as happens when diagonally opposite wheels leave the ground on very uneven rocky ground, the vehicle simply stops.
If you are in a sufficiently low gear to have plenty of spare torque left (to overcome the braking effect) then left foot braking will stop the two spinning wheels and see the vehicle regain grip and make progress.
Normally, only the very modern and expensive 4x4 vehicles have the ability to recover from that situation. With left foot braking in your 'toolbox', any cheap 4x4 suddenly becomes far more capable.
jimf671 said:
In off-road situations with simple 4x4 chassis, left foot braking can be used to enhance traction when the limits of the chassis' compliance is reached. Typically, in a Landrover Defender, you can get it up some serious rocky slopes that would normally only be possible with more complex vehicles.
The LR's achilles heel is that it has a lockable diff only in the centre and no LSD. Therefore, when one wheel at each end is off the ground, as happens when diagonally opposite wheels leave the ground on very uneven rocky ground, the vehicle simply stops.
If you are in a sufficiently low gear to have plenty of spare torque left (to overcome the braking effect) then left foot braking will stop the two spinning wheels and see the vehicle regain grip and make progress.
Normally, only the very modern and expensive 4x4 vehicles have the ability to recover from that situation. With left foot braking in your 'toolbox', any cheap 4x4 suddenly becomes far more capable.
Very interesting - thank you.The LR's achilles heel is that it has a lockable diff only in the centre and no LSD. Therefore, when one wheel at each end is off the ground, as happens when diagonally opposite wheels leave the ground on very uneven rocky ground, the vehicle simply stops.
If you are in a sufficiently low gear to have plenty of spare torque left (to overcome the braking effect) then left foot braking will stop the two spinning wheels and see the vehicle regain grip and make progress.
Normally, only the very modern and expensive 4x4 vehicles have the ability to recover from that situation. With left foot braking in your 'toolbox', any cheap 4x4 suddenly becomes far more capable.
And top lurking!
On a Land Rover experience day a few years ago, driving Discovery 3, it was explained that the clever technology sensed the wheel(s) that had lost traction and delivered the power to those that had traction. "Normal" vehicles just continue to spin-up those wheels losing traction.
Proof of the technology was seen when climbing a steep grass hill, where, running up one side were rollers set into the ground (the sort you often see in warehouses to move goods around), place the nearside wheels of the vehicle on the rollers and of course there's no traction, however amazingly the vehicle climbed the hill as it would be expected to do with traction delivered to the offside wheels only.
Proof of the technology was seen when climbing a steep grass hill, where, running up one side were rollers set into the ground (the sort you often see in warehouses to move goods around), place the nearside wheels of the vehicle on the rollers and of course there's no traction, however amazingly the vehicle climbed the hill as it would be expected to do with traction delivered to the offside wheels only.
titian said:
On a Land Rover experience day a few years ago, driving Discovery 3, it was explained that the clever technology sensed the wheel(s) that had lost traction and delivered the power to those that had traction. "Normal" vehicles just continue to spin-up those wheels losing traction.
Proof of the technology was seen when climbing a steep grass hill, where, running up one side were rollers set into the ground (the sort you often see in warehouses to move goods around), place the nearside wheels of the vehicle on the rollers and of course there's no traction, however amazingly the vehicle climbed the hill as it would be expected to do with traction delivered to the offside wheels only.
Wouldn't traditional limited slip diffs do that?Proof of the technology was seen when climbing a steep grass hill, where, running up one side were rollers set into the ground (the sort you often see in warehouses to move goods around), place the nearside wheels of the vehicle on the rollers and of course there's no traction, however amazingly the vehicle climbed the hill as it would be expected to do with traction delivered to the offside wheels only.
RobM77 said:
titian said:
On a Land Rover experience day a few years ago, driving Discovery 3, it was explained that the clever technology sensed the wheel(s) that had lost traction and delivered the power to those that had traction. "Normal" vehicles just continue to spin-up those wheels losing traction.
Proof of the technology was seen when climbing a steep grass hill, where, running up one side were rollers set into the ground (the sort you often see in warehouses to move goods around), place the nearside wheels of the vehicle on the rollers and of course there's no traction, however amazingly the vehicle climbed the hill as it would be expected to do with traction delivered to the offside wheels only.
Wouldn't traditional limited slip diffs do that?Proof of the technology was seen when climbing a steep grass hill, where, running up one side were rollers set into the ground (the sort you often see in warehouses to move goods around), place the nearside wheels of the vehicle on the rollers and of course there's no traction, however amazingly the vehicle climbed the hill as it would be expected to do with traction delivered to the offside wheels only.
Gary C said:
RobM77 said:
titian said:
On a Land Rover experience day a few years ago, driving Discovery 3, it was explained that the clever technology sensed the wheel(s) that had lost traction and delivered the power to those that had traction. "Normal" vehicles just continue to spin-up those wheels losing traction.
Proof of the technology was seen when climbing a steep grass hill, where, running up one side were rollers set into the ground (the sort you often see in warehouses to move goods around), place the nearside wheels of the vehicle on the rollers and of course there's no traction, however amazingly the vehicle climbed the hill as it would be expected to do with traction delivered to the offside wheels only.
Wouldn't traditional limited slip diffs do that?Proof of the technology was seen when climbing a steep grass hill, where, running up one side were rollers set into the ground (the sort you often see in warehouses to move goods around), place the nearside wheels of the vehicle on the rollers and of course there's no traction, however amazingly the vehicle climbed the hill as it would be expected to do with traction delivered to the offside wheels only.
Max_Torque said:
2) The different effect on dynamic stability because of where the decceleration forces are applied and how they are applied. When you brake, the longitudinal deccel force is reacted into the hubs at wheel centre height, and then reacted fairly evenly across the suspension components into the body shell. When you lift off, the deccel forces are reacted by the powertrain mounts, either resulting in lateral roll or longitudinal pitch moments, with a markedly different(negative) effect on weight transfer
"longitudinal deccel force" can only be produced at the contact point between the tyres and the road. These will all be fed into the 'body' of the car through suspension. So whilst there may be a difference to how the suspension behaves (ie antidive ), the effectively rigid body will receive the same resultant forces (because it has to be a action to the tyre/ground forces). So I struggling with the the assertion that there will be any difference in lateral roll or longitudinal pitch moments. Possibly different movements (because of suspension damping and geometry), but not moments. The resultant moment must counteract the moment on the C of G caused by external forces applied at the tyre/ground.
I equally struggle with the suggestion with difference of weight transfer. The C of G of the vehicle is largely fixed (ignoring secondary changes due to suspension movent) the weight transfer has to be entirely a property of the resultant external forces (again the tyre/ground contact).
I am happy to be challenged. I have always struggled to understand how many (but not all) of the 'benefits' attributed to LFB can actually be explained.
in reviewing this I noticed your use of "dynamic stability" - I have followed a few google links, but am unable to work out what you are actually meaning by the term in this context.
Edited by OverSteery on Friday 18th November 15:19
jimf671 said:
In off-road situations with simple 4x4 chassis, left foot braking can be used to enhance traction when the limits of the chassis' compliance is reached. Typically, in a Landrover Defender, you can get it up some serious rocky slopes that would normally only be possible with more complex vehicles.
The LR's achilles heel is that it has a lockable diff only in the centre and no LSD. Therefore, when one wheel at each end is off the ground, as happens when diagonally opposite wheels leave the ground on very uneven rocky ground, the vehicle simply stops.
If you are in a sufficiently low gear to have plenty of spare torque left (to overcome the braking effect) then left foot braking will stop the two spinning wheels and see the vehicle regain grip and make progress.
Normally, only the very modern and expensive 4x4 vehicles have the ability to recover from that situation. With left foot braking in your 'toolbox', any cheap 4x4 suddenly becomes far more capable.
Top lurking indeed, but this trick is handy in any car with an open differential, especially in automatics since you don't have to worry about clutch control. It's particularly useful in the snow.The LR's achilles heel is that it has a lockable diff only in the centre and no LSD. Therefore, when one wheel at each end is off the ground, as happens when diagonally opposite wheels leave the ground on very uneven rocky ground, the vehicle simply stops.
If you are in a sufficiently low gear to have plenty of spare torque left (to overcome the braking effect) then left foot braking will stop the two spinning wheels and see the vehicle regain grip and make progress.
Normally, only the very modern and expensive 4x4 vehicles have the ability to recover from that situation. With left foot braking in your 'toolbox', any cheap 4x4 suddenly becomes far more capable.
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