trail braking correct or not?
Discussion
car is a stripped out track car xsara vts
theres a route i do quite regularly that involves an open fast left hand 3rd gear hairpin that leads straight onto right hand square 90 degree corner that opens.
i take the hairpin in 3rd gear full accelerator but in order to brake for the 90 right after it id have to come off the throttle and jump on the brakes. this presents a lift off oversteer opertunity for the car so instead while still on the accelerator i brake and then blend out the accelerator and apply more brake. it feels very smooth and the car is balanced for the downshift to second and the corner.
is there a better way to approach this series of corners that i am missing?
theres a route i do quite regularly that involves an open fast left hand 3rd gear hairpin that leads straight onto right hand square 90 degree corner that opens.
i take the hairpin in 3rd gear full accelerator but in order to brake for the 90 right after it id have to come off the throttle and jump on the brakes. this presents a lift off oversteer opertunity for the car so instead while still on the accelerator i brake and then blend out the accelerator and apply more brake. it feels very smooth and the car is balanced for the downshift to second and the corner.
is there a better way to approach this series of corners that i am missing?
"Slower" is indeed the answer for the public road. Really shouldn't be that close to the limit of adhesion when a people carrier full of small children could be just out of sight round the corner.
Generally speaking though the quickest way round a tarmac track is to avoid using the accelerator and brake at the same time. If you know the car's about to step out you need to be ready with the steering to cancel it out. Either that or just be less agressive with your accelerator input - it should only really go into lift-off oversteer with a fairly extreme lift unless you have it set up to be as twitchy as a gravel rally car, which probably isn't appropriate for a road car that's driven close to the limit.
Generally speaking though the quickest way round a tarmac track is to avoid using the accelerator and brake at the same time. If you know the car's about to step out you need to be ready with the steering to cancel it out. Either that or just be less agressive with your accelerator input - it should only really go into lift-off oversteer with a fairly extreme lift unless you have it set up to be as twitchy as a gravel rally car, which probably isn't appropriate for a road car that's driven close to the limit.
If these bends were on a race track, you'd adjust your line to give you an opportunity to brake for the second bend in a straight line. I'd have to see the bends to know if this is possible, but there are many sequences out there on race tracks which some people feel require braking on a curve, but in actual fact it's possible to brake later and gain time by straight lining the braking area. I'm thinking Surtees/Clearways at Brands Indy, The Esses at Snetterton, or Maggots/Beckets at Silverstone National. There are of course some corners on tighter race tracks which don't allow this technique, such as the chicane on the back straight at Curborough. Your technique interests me though: in a front wheel drive car, by braking and accelerating at the same time you are changing the brake distribution, because the power cuts back on the braking at the front, leaving more bias to the rear, which actually makes your oversteer situation worse. Instead of left foot braking, try smoothing out your control inputs, thinking about your lines and the relationshiop between the steering and the balance of the car (i.e. steer less if the balance shifts towards oversteer to keep the car's trajectory the same). Left foot braking is a very advanced technique and it should be possible to approach a sequence such as you describe with basic techniques. Trail braking though is actually something completely different (braking into a corner) - you've just described left foot braking...
However, this bend is on the public road. I'd suggest doing all of the above to keep proper control of the car, but then lower your speed significantly to improve your safety. If you're currently barrelling round this sequence at 50mph, then choosing a speed of 30mph will make you safer, and if you follow a good technique for car control such as described above, which would allow you to increase the potential speed to, for example, 60mph, then by still sticking at 30mph you've just increased your safety margin by 30%.
My advice is to become aware of the balance of the car and the ideal lines etc, as you clearly want to do, but keep the speed low and keep it safe. As your balance and car control skills increase, you should gradually improve your safety on the road, not your speed. Then, book a track day or some karting where you can practise your technique at high speed. Good technique in any sport is about practising more than applying. For example, my swimming coach gives me more weird drills than she gives me actual swimming!
Track days, karting and motorsport are expensive of course, but you have two sensible options: you either love motorsport and pay the cost to drive fast on a track, or you give up driving fast. By all means be aware of the balance of the car though, just at a lower speed. The risk of hitting a poor innocent person on the road are just too great, and it's just not worth it to half satisfy your urge to go fast (and on a road in a road car you'll only ever half satisfy this urge, so it's not really worth it).
However, this bend is on the public road. I'd suggest doing all of the above to keep proper control of the car, but then lower your speed significantly to improve your safety. If you're currently barrelling round this sequence at 50mph, then choosing a speed of 30mph will make you safer, and if you follow a good technique for car control such as described above, which would allow you to increase the potential speed to, for example, 60mph, then by still sticking at 30mph you've just increased your safety margin by 30%.
My advice is to become aware of the balance of the car and the ideal lines etc, as you clearly want to do, but keep the speed low and keep it safe. As your balance and car control skills increase, you should gradually improve your safety on the road, not your speed. Then, book a track day or some karting where you can practise your technique at high speed. Good technique in any sport is about practising more than applying. For example, my swimming coach gives me more weird drills than she gives me actual swimming!
Track days, karting and motorsport are expensive of course, but you have two sensible options: you either love motorsport and pay the cost to drive fast on a track, or you give up driving fast. By all means be aware of the balance of the car though, just at a lower speed. The risk of hitting a poor innocent person on the road are just too great, and it's just not worth it to half satisfy your urge to go fast (and on a road in a road car you'll only ever half satisfy this urge, so it's not really worth it).
It's truly impossible to give any accurate detailed advice without knowing the road and driving the car to get a feeling for its individual handling characteristics.
I am curious to know however what your left foot does when you change gear from third into second. If it is still on the brake how do you use the clutch? If it on the clutch it seems that you must have a period when you are not braking as your right foot comes across to the brake from the gas. You could of course be using this separation between braking and gear change to stabilise the car but that is not really the best way to do it if you are seeking maximum corner speed, which would appear to be your goal.
As ever, investing time and money in yourself and paying for instruction instruction from someone who knows what they are doing will ultimately make you much faster and smoother than spending money on your car or practising inefficient overcomplicated techniques.
Hope this helps
Best regards
Martin A
I am curious to know however what your left foot does when you change gear from third into second. If it is still on the brake how do you use the clutch? If it on the clutch it seems that you must have a period when you are not braking as your right foot comes across to the brake from the gas. You could of course be using this separation between braking and gear change to stabilise the car but that is not really the best way to do it if you are seeking maximum corner speed, which would appear to be your goal.
As ever, investing time and money in yourself and paying for instruction instruction from someone who knows what they are doing will ultimately make you much faster and smoother than spending money on your car or practising inefficient overcomplicated techniques.
Hope this helps
Best regards
Martin A
When i had my french fwd hothatch, then i regularly would left foot brake, or at least be covering the brake with my left foot, on the entrance to a corner. By brakeing rather than lifting the accelerator, the trailing arm rear suspension actually pulls the rear of the car downwards, and tends to prevent LOOS from occuring. Even when just trundling along, covering the brake with me left foot, meant that if something did happen unexpectedly (like a tractor pulling out etc etc) then i could just transistion into a full ABS stop without so much as a wobble from the rear. (and a quick blip of the accelerator to get to neutral drive torque, allows you to just knock the trans into neutral to avoid a stall and maximise the ABS cycle frequency as the engine inertia is disconencted from the wheels)
(it also takes something like 100ms to lift and transfer to the brake, and if you're doing this in a rush (think windscreen quickly filling with the nasty view of a large tractor :-) you cannot really do it smoothly or progresivly etc)
(it also takes something like 100ms to lift and transfer to the brake, and if you're doing this in a rush (think windscreen quickly filling with the nasty view of a large tractor :-) you cannot really do it smoothly or progresivly etc)
Hi m4rk,
If you like driving quickly like this, then I very highly recommend one of the Advanced Handling days with RideDrive
Utterly brilliant day out and skill boost: www.ridedrive.co.uk/shop-high-performance.htm
You'll have a blast, heighten your driving skills way more than you can image and be smoother and quicker
If you like driving quickly like this, then I very highly recommend one of the Advanced Handling days with RideDrive
Utterly brilliant day out and skill boost: www.ridedrive.co.uk/shop-high-performance.htm
You'll have a blast, heighten your driving skills way more than you can image and be smoother and quicker
Edited by SVS on Saturday 4th September 19:37
Max_Torque said:
When i had my french fwd hothatch, then i regularly would left foot brake, or at least be covering the brake with my left foot, on the entrance to a corner. By brakeing rather than lifting the accelerator, the trailing arm rear suspension actually pulls the rear of the car downwards, and tends to prevent LOOS from occuring.
This really does scare me. The whole point of left foot braking is to shift the effective brake balance way to the rear, massively increasing the amount of oversteer available on deceleration. The technique was developed for use in Saab rally cars which had handbrakes that acted on the front wheels, making handbrake turns impossible, so a replacement was needed. If you can show me how deceleration of any kind would do anything other than unload the rear wheels I would be grateful.
davepoth said:
Max_Torque said:
When i had my french fwd hothatch, then i regularly would left foot brake, or at least be covering the brake with my left foot, on the entrance to a corner. By brakeing rather than lifting the accelerator, the trailing arm rear suspension actually pulls the rear of the car downwards, and tends to prevent LOOS from occuring.
This really does scare me. The whole point of left foot braking is to shift the effective brake balance way to the rear, massively increasing the amount of oversteer available on deceleration. The technique was developed for use in Saab rally cars which had handbrakes that acted on the front wheels, making handbrake turns impossible, so a replacement was needed. If you can show me how deceleration of any kind would do anything other than unload the rear wheels I would be grateful.
davepoth said:
Max_Torque said:
When i had my french fwd hothatch, then i regularly would left foot brake, or at least be covering the brake with my left foot, on the entrance to a corner. By brakeing rather than lifting the accelerator, the trailing arm rear suspension actually pulls the rear of the car downwards, and tends to prevent LOOS from occuring.
This really does scare me. The whole point of left foot braking is to shift the effective brake balance way to the rear, massively increasing the amount of oversteer available on deceleration. The technique was developed for use in Saab rally cars which had handbrakes that acted on the front wheels, making handbrake turns impossible, so a replacement was needed. If you can show me how deceleration of any kind would do anything other than unload the rear wheels I would be grateful.
Also, your last statement is incorrect. Left foot braking is not intended to decelerate the car and therefore induce weight transfer to unload the rear wheels and cause oversteer. The speed is intended to stay the same, and the balance effects in the car are purely down to the engine fighting the brakes.
Trail braking is an establishing technique to use in sharply angled corners but generally sparingly- and on a track!
I was taught it at Millbrook by Colin Hoad (CAT Driver Training) who's an expert, though I'm not- and he would definitely say it's only for the track unless you get it all completely tits up in a road corner.
I was taught it at Millbrook by Colin Hoad (CAT Driver Training) who's an expert, though I'm not- and he would definitely say it's only for the track unless you get it all completely tits up in a road corner.
Lakeland9 said:
Trail braking is an establishing technique to use in sharply angled corners but generally sparingly- and on a track!
I was taught it at Millbrook by Colin Hoad (CAT Driver Training) who's an expert, though I'm not- and he would definitely say it's only for the track unless you get it all completely tits up in a road corner.
Are you sure you're not confusing the need for greater overlap between brakes and steering on a slower corner, due to the speed component of weight transfer being lower; with trailbraking, as used to great effect by Jim Clark and Michael Schumacher in all corners, fast or slow? The reason I say that is that trailbraking isn't just a technique for "sharply angled" corners.I was taught it at Millbrook by Colin Hoad (CAT Driver Training) who's an expert, though I'm not- and he would definitely say it's only for the track unless you get it all completely tits up in a road corner.
Lakeland9 said:
Might be for them, Rob but not for me, I think. In any event, aren't most corners, brake, turn-in then power?
Yes, although only enough power to balance the car (maintain speed), otherwise you'll just get armfuls understeer - you should only accelerate (increase speed) with a commensurate unwinding of the steering, after the apex. Also, when you turn in, if you come off the brakes and then turn in, you'll also get armfuls of understeer. The correct track technique is to blend one into the other, which is taught from the basic ARDS test upwards, so as you back off the brake, you turn the steering - they move together, almost as if connected. The timing of this blending changes the balance of the car on turn-in, and the steady throttle then maintains that balance until you pass the apex and start accelerating out of the corner. In a road car at safe speeds you won't obviously get understeer or oversteer in terms of visibibly sliding, but the balance of the car will still be towards understeer/oversteer, which will compromise your ability to deal with an emergency situation and also wear out your front tyres - it's better to be balanced, and I use these techniques on the road all the time. The key message is to treat the steering and brakes/throttle as connected - never add one without taking away the other.That's the standard technique. Trailbraking is different; it's an advanced technique which involves staying on the brakes after turn-in, often right up to the apex. These days it's often combined with left foot braking, which incidentally is one of the many things that distinguished Michael Schumacher from the rest - the mastery of that technique.
Hi All
There is no weight transfer to the rear, just a reduction of weight transfer to the front. This is often perceived as weight transfer to the rear. Sadly very few instructors are aware of the fact that personal perceptions are often out of line with objective reality and myths persist. This confuses the understanding of vehicle handling, even if other aspects of instruction result in improved car control.
Hope this helps
Best regards
Martin A
davepoth said:
Fair points both, but still, how does left foot braking rather than lifting the accelerator (which to my mind would still imply the OP was intending to lose speed) cause a weight transfer to the back?
Left foot braking adds a deceleration component at the rear wheels. The torque reaction at the front will therefore be less than when the same deceleration is caused solely by engine braking. Consequently the nose will not dive as much and by the same token the rear will not rise.There is no weight transfer to the rear, just a reduction of weight transfer to the front. This is often perceived as weight transfer to the rear. Sadly very few instructors are aware of the fact that personal perceptions are often out of line with objective reality and myths persist. This confuses the understanding of vehicle handling, even if other aspects of instruction result in improved car control.
Hope this helps
Best regards
Martin A
There is also one other very important point to make in relation to left foot braking and road cars. Which is, i have never driven a std set up road car (espec a fwd one) that actually has enough rear brake bias to actually lock (or set up a high enough tyre slip ratio) a rear wheel when lfb'ing. When you see the rally footage of fwd cars sliding round when being lfb'd, they have a massive amount of rear bias to enable this. In conjunction with the rear load limiting valve, every road car i will lock the fronts (and push out wide) well before the rear goes (i'm talking about steady state cornering here, obviously if you chuck the car hard enough into a turn then stab the brakes the yaw momentum might be significant to unsettle the rear) Also, should you get unexpected rear tyre slip (and i'm talking trackdays etc here rather than road) you have a almost zero time delay before you can re-assert torque at the front wheels to help stabilise the front/rear tyre slip coefficient. (just come off the brakes, throttle is already on)
And finally, another reason LFB'ing stabilises rather than unstabilises is that it keeps the drivetrain wound up - always in "positive" torque direction, so the systen does not cross the lash zone (which in my old french 130k mile hatch was pretty wide lol) and avoid the snatch (lash + engine mount deflection) as this happens
I think if you can genuinely master it, LFB is great, you have 2 feet, use them!! (on my rally car in stage, the most difficult thing for me to get right was high speed limit braking with my left foot, because after 20 years of driving, arriving at 100+ mph corners, you instinctively start to move the right foot to cover the brake (this give confidence as you lift earlier) to maximise LFB advantage you need to keep the right foot hard on the accelerator till the absolute last moment, then quickly but smoothly brake with left foot BEFORE lifting off, (effectively moves the lift off point towards the apex)
Regarding gear changing when LFB'ing, in my rally car it's easy as it's a sequntial paddle dog shift (no lift or blip required by driver!) but in my road car, i just start the braking with my left foot, feather out the (right foot)throttle as the weight transfer stabilises the car on the front axle, then using a heal and toe kinda feet position i start to take the brake force off my left foot and onto my right foot (both feet share the brake pedal), then move left foot to clutch, blip throttle in conventional H'n'Toe manner, and shift down. This also i find helps to avoid the natural tendancy to try to get the lower gear too early in the braking zone (leading to over revs / instabliity etc)
In this way there is no interuption in brake force, a smooth blend of throttle torque and a nicely rev match downshift, i can now do it so smoothly you can't even feel the shift or foot movements in the car, in fact my passengers don't notice, most just say "oooh, isnt you car smooth" when i think they mean " gosh, nice to have a driver with some co-ordination for a change".... ;-)
And finally, another reason LFB'ing stabilises rather than unstabilises is that it keeps the drivetrain wound up - always in "positive" torque direction, so the systen does not cross the lash zone (which in my old french 130k mile hatch was pretty wide lol) and avoid the snatch (lash + engine mount deflection) as this happens
I think if you can genuinely master it, LFB is great, you have 2 feet, use them!! (on my rally car in stage, the most difficult thing for me to get right was high speed limit braking with my left foot, because after 20 years of driving, arriving at 100+ mph corners, you instinctively start to move the right foot to cover the brake (this give confidence as you lift earlier) to maximise LFB advantage you need to keep the right foot hard on the accelerator till the absolute last moment, then quickly but smoothly brake with left foot BEFORE lifting off, (effectively moves the lift off point towards the apex)
Regarding gear changing when LFB'ing, in my rally car it's easy as it's a sequntial paddle dog shift (no lift or blip required by driver!) but in my road car, i just start the braking with my left foot, feather out the (right foot)throttle as the weight transfer stabilises the car on the front axle, then using a heal and toe kinda feet position i start to take the brake force off my left foot and onto my right foot (both feet share the brake pedal), then move left foot to clutch, blip throttle in conventional H'n'Toe manner, and shift down. This also i find helps to avoid the natural tendancy to try to get the lower gear too early in the braking zone (leading to over revs / instabliity etc)
In this way there is no interuption in brake force, a smooth blend of throttle torque and a nicely rev match downshift, i can now do it so smoothly you can't even feel the shift or foot movements in the car, in fact my passengers don't notice, most just say "oooh, isnt you car smooth" when i think they mean " gosh, nice to have a driver with some co-ordination for a change".... ;-)
Edited by anonymous-user on Friday 10th September 15:42
sorry if this is someone on here 4.14 seconds in
http://www.youtube.com/watch?v=ulRu-9CANmk being on the brakes and gently letting out the throttle would have prevented this as it looks like a lift off oversteer event.
http://www.youtube.com/watch?v=ulRu-9CANmk being on the brakes and gently letting out the throttle would have prevented this as it looks like a lift off oversteer event.
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