Under Steer Control via Left Foot or Steering Input/Throttle
Discussion
Hi
This is my first post so please be gentle with me :-)
I drive a FWD car with no ABD, TC and ABS with an open diff. Most articles on controlling under steer, from road driving manuals, advocate reducing throttle input and backing off the steering wheel angle. Books focused on ice, snow or rally driving advocate keeping the throttle open and using your left foot on the brakes to throw the weight of the car forward, increasing traction to the front wheels. I have used both methods on a dry surface with good results. What would you recommend to control under steer on a surface with plenty of grip? Is left foot braking recommended for offroad use only? Or are both methods valid and safe on-road?
Thanks
This is my first post so please be gentle with me :-)
I drive a FWD car with no ABD, TC and ABS with an open diff. Most articles on controlling under steer, from road driving manuals, advocate reducing throttle input and backing off the steering wheel angle. Books focused on ice, snow or rally driving advocate keeping the throttle open and using your left foot on the brakes to throw the weight of the car forward, increasing traction to the front wheels. I have used both methods on a dry surface with good results. What would you recommend to control under steer on a surface with plenty of grip? Is left foot braking recommended for offroad use only? Or are both methods valid and safe on-road?
Thanks
Welcome to PH 
In my experience, you should only ever look for one solution at a time for any handling problems, so in order to correct understeer in a FWD car, just ease off the gas, the car should tighten its line without the need for any steering change. Note don’t lift off quickly as this can induce oversteer and maybe a spin. Moving the steering back towards the centre might help regain some grip, but it depends whether you’re in an emergency situation or not.
I wouldn’t recommend left-foot braking for the road, unless you’ve already learned how to do it in a safe environment, where you can spin in safety. In any case, I can’t imagine that left foot braking would give you any benefit except on a race track.
In my experience, you should only ever look for one solution at a time for any handling problems, so in order to correct understeer in a FWD car, just ease off the gas, the car should tighten its line without the need for any steering change. Note don’t lift off quickly as this can induce oversteer and maybe a spin. Moving the steering back towards the centre might help regain some grip, but it depends whether you’re in an emergency situation or not.
I wouldn’t recommend left-foot braking for the road, unless you’ve already learned how to do it in a safe environment, where you can spin in safety. In any case, I can’t imagine that left foot braking would give you any benefit except on a race track.
Hi
Thanks for the replies.
I find left foot braking a quicker way to control under steer than backing the steering and/or throttle off on a dry surface. If the conditions are very slippery ABS often gets in the way of left foot braking though. I would sooner practice the recommended method on a skid pan and so I will concentrate on the steering/throttle method.
Cheers!!
Thanks for the replies.
I find left foot braking a quicker way to control under steer than backing the steering and/or throttle off on a dry surface. If the conditions are very slippery ABS often gets in the way of left foot braking though. I would sooner practice the recommended method on a skid pan and so I will concentrate on the steering/throttle method.
Cheers!!
A lot of people think they know how to left-foot brake, but can't do it to save their life (literally).
Don't use left-foot braking, unless you have learnt to do it since you first learnt to drive. Otherwise, get at least several days of full-time practice in an open area before trying it under normal road conditions. Then you will need several months of regular usage before you can even contemplate using it in an emergency situation.
I learnt LFB since the first time I ever drove a four-wheeled vehicle (a go-kart), and it's still a bit awkward doing in it a road car, 11 years later, despite using LFB in a variety of other types of vehicles.
While it's all fine and dandy to feel like you're doing LFB well in the relatively safety of a quiet road, car park, or skid pan, trying to do it in a life-threatening emergency is completely another.
Don't over-estimate yourself. In an emergency, it's best to stick to simple techniques. Just back off the throttle and progressively unwind the wheel, if you find yourself under-steering.
LFB is a preventative technique. It prevents understeer. Correcting understeer after the fact, is not accomplished by LFB.
LFB was designed to allow more responsive turn-in, by allowing the driver to destablise the rear of the vehicle under braking, whilst maintaining throttle. This was quite important in the days of 4WD rally cars with primitive turbo-chargers. Drivers had to find a way to fight the severe understeer of these cars, and come up with a way to keep the turbo spinning even when the vehicle was under braking.
In lose-surface rallying, LFB initiates a rear-end drift so that the car pivots around at a rate chosen by the driver, while throttle is maintained to power the car toward the exit. Like the Scandinavian Flick, Throttle Lift-Off, and the Hand-brak Turn, it is a technique used under specific circumstances. In rallying, this means medium-speed corners where braking is needed but no gear down-change is necessary.
LFB on dry tarmac is rare and probably unnecessary (IMHO). In fact, some racing coaches reject it entirely.
If you are understeering at mid-corner or after turn-in (I'm talking about racing/rallying or other high-performance driving situations), then LFB will not help you, since your first priority will be to lose speed in the quickest possible time, to avoid flying off the road/track/stage. You achieve this by:
1. Getting off the throttle entirely, and getting your brake pedal down hard and fast, tipping the weight forward and letting your front tyres dig into the road/track/stage.
2. Hopefully, the car will turn a bit more into the direction you want, and will also scrub off all the excess speed.
3. Once you feel that there is no more extra steering effort to be gained by this sudden weight-transfer, quickly but progressively release the brakes, while quickly but progressively unwinding the steering wheel, until the car begins to regain traction.
4. Once traction is regained, press the brakes again, and wind the steering into the direction you wish to travel. Again, this should be quick but progressive. Think of cadence braking, but you're doing it with both steering and brakes.
All of the above four steps should be able to accomplished in less two seconds. Any longer, and you will probably be beyond the point of no return.
Unless you were driving like a numbskull, you should be able to regain full control by the end of Step 2. If ever you need to go all the way to Step 4, remedial driver training would be strongly recommended.
If you ever get the opportunity to practice in a wide, open space, avoid the common but useless practice of merely skidding around like a lunatic. Practice progressive steering, braking, and acceleration. Get used to dancing around the edge of traction, by practicing cadence braking, braking and steering, and using the throttle to power yourself out of trouble. Learn to make quick but progressive adjustments to braking and steering. All of this can be done at under 60km/h, or even slower in the wet.
>> Edited by Jungles on Thursday 29th December 01:56
Don't use left-foot braking, unless you have learnt to do it since you first learnt to drive. Otherwise, get at least several days of full-time practice in an open area before trying it under normal road conditions. Then you will need several months of regular usage before you can even contemplate using it in an emergency situation.
I learnt LFB since the first time I ever drove a four-wheeled vehicle (a go-kart), and it's still a bit awkward doing in it a road car, 11 years later, despite using LFB in a variety of other types of vehicles.
While it's all fine and dandy to feel like you're doing LFB well in the relatively safety of a quiet road, car park, or skid pan, trying to do it in a life-threatening emergency is completely another.
Don't over-estimate yourself. In an emergency, it's best to stick to simple techniques. Just back off the throttle and progressively unwind the wheel, if you find yourself under-steering.
LFB is a preventative technique. It prevents understeer. Correcting understeer after the fact, is not accomplished by LFB.
LFB was designed to allow more responsive turn-in, by allowing the driver to destablise the rear of the vehicle under braking, whilst maintaining throttle. This was quite important in the days of 4WD rally cars with primitive turbo-chargers. Drivers had to find a way to fight the severe understeer of these cars, and come up with a way to keep the turbo spinning even when the vehicle was under braking.
In lose-surface rallying, LFB initiates a rear-end drift so that the car pivots around at a rate chosen by the driver, while throttle is maintained to power the car toward the exit. Like the Scandinavian Flick, Throttle Lift-Off, and the Hand-brak Turn, it is a technique used under specific circumstances. In rallying, this means medium-speed corners where braking is needed but no gear down-change is necessary.
LFB on dry tarmac is rare and probably unnecessary (IMHO). In fact, some racing coaches reject it entirely.
If you are understeering at mid-corner or after turn-in (I'm talking about racing/rallying or other high-performance driving situations), then LFB will not help you, since your first priority will be to lose speed in the quickest possible time, to avoid flying off the road/track/stage. You achieve this by:
1. Getting off the throttle entirely, and getting your brake pedal down hard and fast, tipping the weight forward and letting your front tyres dig into the road/track/stage.
2. Hopefully, the car will turn a bit more into the direction you want, and will also scrub off all the excess speed.
3. Once you feel that there is no more extra steering effort to be gained by this sudden weight-transfer, quickly but progressively release the brakes, while quickly but progressively unwinding the steering wheel, until the car begins to regain traction.
4. Once traction is regained, press the brakes again, and wind the steering into the direction you wish to travel. Again, this should be quick but progressive. Think of cadence braking, but you're doing it with both steering and brakes.
All of the above four steps should be able to accomplished in less two seconds. Any longer, and you will probably be beyond the point of no return.
Unless you were driving like a numbskull, you should be able to regain full control by the end of Step 2. If ever you need to go all the way to Step 4, remedial driver training would be strongly recommended.
If you ever get the opportunity to practice in a wide, open space, avoid the common but useless practice of merely skidding around like a lunatic. Practice progressive steering, braking, and acceleration. Get used to dancing around the edge of traction, by practicing cadence braking, braking and steering, and using the throttle to power yourself out of trouble. Learn to make quick but progressive adjustments to braking and steering. All of this can be done at under 60km/h, or even slower in the wet.
>> Edited by Jungles on Thursday 29th December 01:56
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