A question of balance

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R_U_LOCAL

Original Poster:

2,676 posts

207 months

Tuesday 6th March 2007
quotequote all
What on earth do we mean when we talk about "balance" when driving a car? It's not like you can fall off it. Well, you can fall off the road of course, but not in the same way as the organ-donors who dust off their Tamajaki ZRZ900s every April and throw themselves around the countryside at warp factor 9.

Balance is an absolutely essential ingredient of high performance driving, and it's not a skill you can learn overnight. It's one that you need to practise, and occasionally get wrong in order to learn correctly. But first off, here's my explanation of balance as applied to driving a car. And before any of you physics pedants start (you know who you are), I know the correct terms for this will include "mass", "acceleration", "force" and no end of other scientific terms, but I'll be sticking with "weight" for now, as I'm a simple man and it's a complicated subject.

Balance is the ability of a driver to control a car in such a way that the transfer of weight involved in accelerating, braking and cornering does not lead to a loss of control.

Blimey - I think I've just written a definition! *Note to self - ring the publishers of "Roadcraft" tomorrow morning*

It's fairly obvious (and actually is written in Roadcraft) that a moving car is at it's most stable when travelling in a straight line at a constant speed. Any action that the driver takes to alter that state - increasing or decreasing speed and cornering - will transfer the vehicle's weight around the car. Braking, for instance, will transfer the vehicle's weight forwards. This will have two fairly obvious outcomes - there will be more weight pressing the front tyres into the road, and less weight pushing the back tyres into the road.

Imagine for a moment that you're driving a car with two boots - a Mk1 Toyota MR2 for instance. If you went out and bought a couple of sacks of potatoes and stuck them in the front boot, then the car would handle very differently than if you put them in the rear boot. If you're a fast driver, then you're effectively shifting those sacks of spuds into the front boot every time you brake, and chucking them in the back every time you accelerate.

Now, I'm not saying that the transfer of weight is a bad thing - far from it. In fact, it's an utterly unavoidable consequence of moving a ton-and-a-half of car along a road. Without it, none of us would enjoy driving high performance cars, as it's the transfer of weight which produces the sensations of speed that we all love - the hard cornering, the shove in the back under acceleration, and the dive under braking.

No - the transfer of weight isn't the problem. What is the problem, is how you transfer that weight.

Let's look at braking first, as it's a fairly simple operation in a car (none of this twiddling hand and foot levers that the organ donors have to do) involving pressing a pedal. That's it - you just press a pedal and the car slows down.

Well, not exactly. If you just jumped on the brake pedal really hard every time you braked, you wouldn't last very long. You'd get a sore right leg, it wouldn't do your car much good, and I'd give you 10 minutes before a taxi ran up your rear. The other problem when applying the brakes as though they are a switch is that pressing the brake pedal hard and fast transfers the vehicles weight forwards hard and fast. This can unsettle the rear end of the car and leave very little front-end grip left for steering.

The correct technique when braking is to start applying the brakes gently, and then firm up the pedal pressure as you go. I'm not talking about building up the pressure over several seconds - you should be able to do it smoothly in less than a second. You can use this technique even when braking very hard - the amount of weight you're transferring forwards is just the same as if you jumped on the pedal, but if you're smooth in your brake application, that weight transfer takes slightly longer, and that's what allows you to keep better control of the car. This is what I'd describe as "balancing" the car under braking.

Whilst we're on the subject of braking, it's just as important to be smooth coming off the brakes as it is to be smooth when applying them. It's relatively easy to learn how to press the pedal smoothly, but when you're steaming on, your attention is always on "what's next?", and it's very easy to just jump off the brakes and move straight back onto the accelerator for the next corner. Don't forget that you've transferred all that weight forwards when braking, and when you come off the brakes, it will settle rearwards again. Jumping off the brake will suddenly release weight from the front of the car, and if you're entering a corner, this can be disastrous. A much better technique is to ease off the brake pedal, which moves that weight rearwards at a slower rate, and helps to keep the car balanced. My instruction to students is never "off the brakes" - it's always "ooooofffff the brakes". They look at me as though I'm retarded - granted - but they get the idea.

The same is true for acceleration. If you just jump on and off the throttle, particularly if you drive a powerful car, then the resultant weight transfer can move around too quickly and unsettle the car. Take lift-off oversteer as an example. If a driver is pressing on in a corner, close to the cars limit, and has to suddenly tighten their line, then the car is liable to start sliding. If that driver then reacts badly and lifts off the accelerator in a panic, then the weight will inevitably move towards the front of the car and, more importantly, away from the rear, which will put the car into an oversteer situation that will take some skill and clear thinking from which to recover. The average driver's usual response at this point will be to hit the brakes, which, of course, transfers more weight forwards, and will pitch the car into a spin.

In a similar situation, a good driver will feather back slightly on the throttle, and use the accelerator to move the weight around to their advantage, rather than to their disadvantage. The key, as with most aspects of performance driving, is to do it smoothly.

It's the same with steering.

I reported a fatal accident a coupe of years ago in which a young driver lost control of his car whilst negotiating a bend on an NSL road at high speed. As part of the investigation, we prepared a video of the scene to be played in court. I demonstrated that a similar car could be driven through the bend almost 20mph faster than the speed at which the young driver had lost control. It wasn't a problem because my style of driving is smooth, whereas marks at the scene showed that this lad had chucked the car into the corner, and the manner in which he'd done it had put the car out of control.

Here's another nice little line.

If you sneak up on your car and make it jump, it'll throw a strop, but if you tell it what you're going to do, and ease it into it, it'll do whatever you want.

So there you go - keep your balance.

negative creep

24,942 posts

226 months

Tuesday 6th March 2007
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does the car being front, rear or all wheel drive have much bearing on this?

R_U_LOCAL

Original Poster:

2,676 posts

207 months

Tuesday 6th March 2007
quotequote all
negative creep said:
does the car being front, rear or all wheel drive have much bearing on this?


The driven end(s) are what give a car it's tendency at the limit. As a general rule, RWD cars tend to oversteer, FWD cars tend to understeer, and 4WD cars react based on a combination of the layout of the car they are based on and the torque bias of their 4WD system.

Every car is different though - older Peugeots, for instance, are very throttle-sensitive when cornering, and will oversteer quite easily. Conversely,modern BMWs have a tendency to initially understeer when approaching the limit.

Another essential factor to consider is the position of the engine and gearbox. Older Audi Quattros used to have their engine way out over the front axle line, whereas we all know about the handling idiosyncrasies of the Porsche 911 with it's engine mounted a few inches inboard of the back bumper.

Every car has different tendencies, and a different "feel" to them. Even identical cars can feel quite different to drive. The essential technique across all car types, though, is the smooth use of the controls, and the gradual, rather than sudden application of inputs.

Major Bloodnok

1,561 posts

214 months

Tuesday 6th March 2007
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Excellent explanation. These need to be preserved somewhere.

Oh, and "weight" is the correct word, since it's a force. It would be wrong to say that you're shifting mass around.

TripleS

4,294 posts

241 months

Tuesday 6th March 2007
quotequote all
R_U_LOCAL said:
negative creep said:
does the car being front, rear or all wheel drive have much bearing on this?


The driven end(s) are what give a car it's tendency at the limit. As a general rule, RWD cars tend to oversteer, FWD cars tend to understeer, and 4WD cars react based on a combination of the layout of the car they are based on and the torque bias of their 4WD system.

Every car is different though - older Peugeots, for instance, are very throttle-sensitive when cornering, and will oversteer quite easily. Conversely,modern BMWs have a tendency to initially understeer when approaching the limit.

Another essential factor to consider is the position of the engine and gearbox. Older Audi Quattros used to have their engine way out over the front axle line, whereas we all know about the handling idiosyncrasies of the Porsche 911 with it's engine mounted a few inches inboard of the back bumper.

Every car has different tendencies, and a different "feel" to them. Even identical cars can feel quite different to drive. The essential technique across all car types, though, is the smooth use of the controls, and the gradual, rather than sudden application of inputs.


Another very nice post Reg, thank you.

Incidentally, if I understand him correctly, StressedDave tells us that all modern cars are designed to understeer, as this is considered easier for most normal drivers to cope with and thus it is deemed inherently safer.

To me this seems odd really, because I've always felt happier about a car that oversteers rather than understeers, as I have this horror of going straight on at a bend - especially a LH bend - not that I have actually had much of that trouble, fortunately. Anyhow I expect a lot of very clever people have sorted this out, so I'm maybe wrong in my reasoning and there are factors I'm not appreciating. It's just a personal feeling after all.

I suppose I'm thinking back to the days with the Austin-Healey Sprites and the Jaguars, where I used to enjoy helping the tail round on low speed bends and roundabouts on a damp road - all fairly innocent stuff really. These days I expect that would get me a ticket!

Best wishes all,
Dave.

waremark

3,241 posts

212 months

Tuesday 6th March 2007
quotequote all
Great writing again Reg, thank you. I certainly agree with whoever said that these posts of yours should be preserved. Would you consider offering them to the Advanced Driving UK web site for preservation?

I am interested that you have not mentioned: 'balancing the car with gas in a corner' - a far more simplistic but more common use of the term 'balancing'.

Most of the Roadcraft section on cornering deals with cornering with restricted vision, where the point at which the speed should be lowest is just before corner entry. In this scenario, Roadcraft teaching is to go back on the gas gently just before turn in, to maintain speed while the distance you can see remains constant, and then to increase the gas to accelerate to a suitable pace for the next section of road as you approach the end of the corner and the distance you can see extends (in Roadcraft speak 'the limit point starts to move away more quickly'). Both my IAM and Rospa examiners have called the use of gas in the corner in this way: 'balancing the car with the accelerator'.

Do you agree with this terminology? Do you teach students to corner in this style even where there is open vision through a corner? Planning to get back on the gas just before turn in makes sure that your entry speed is low enough, and it is a comfortable style of cornering for passengers, but it contrasts with the race technique of turning in off the gas and perhaps under trail braking.

GreenV8S

30,149 posts

283 months

Tuesday 6th March 2007
quotequote all
TripleS said:
StressedDave tells us that all modern cars are designed to understeer, as this is considered easier for most normal drivers to cope with and thus it is deemed inherently safer.

To me this seems odd really, because I've always felt happier about a car that oversteers rather than understeers, as I have this horror of going straight on at a bend


As somebody once put it:

Oversteer is frightning for the passengers.
Understeer is frightening for the driver.

warren182

1,088 posts

209 months

Tuesday 6th March 2007
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Another excellent article. After I had some tuition and learnt to play around with the balance of the car, I enjoyed my car so much more.

chris_tivver

583 posts

205 months

Tuesday 6th March 2007
quotequote all
GreenV8S said:
TripleS said:
StressedDave tells us that all modern cars are designed to understeer, as this is considered easier for most normal drivers to cope with and thus it is deemed inherently safer.

To me this seems odd really, because I've always felt happier about a car that oversteers rather than understeers, as I have this horror of going straight on at a bend


As somebody once put it:

Oversteer is frightning for the passengers.
Understeer is frightening for the driver.

I think the logic is because of what Reg said: if an inexperienced/uninformed driver gets into trouble in a corner then the immediate reaction is to lift off the throttle. If you design the car to understeer then that will be the correct thing to do.

For me the epiphany was when the Silverstone instructors taught me to carry some brake into a slow corner so that the weight stayed forward and it cured the understeer problem I had been having on that corner.
They also taught me that you should not consider a car as one that understeers or oversteers - it depends on what the driver does. Certainly by being a bit careless/over-careful at Longcross last year I managed to get understeer in the (usually oversteering) Tuscan and was too slow to correct and ended up in the bushes eek. Admittedly we were water-skiing that weekend but I can induce understeer in the dry as well.

R_U_LOCAL

Original Poster:

2,676 posts

207 months

Wednesday 7th March 2007
quotequote all
waremark said:
Great writing again Reg, thank you. I certainly agree with whoever said that these posts of yours should be preserved. Would you consider offering them to the Advanced Driving UK web site for preservation?


I don't have a problem with these posts being posted elsewhere - I've put them in the public domain and the more people who read them and comment on them, the better. I'd just ask that you forward me a link to where they're posted.

waremark said:
I am interested that you have not mentioned: 'balancing the car with gas in a corner' - a far more simplistic but more common use of the term 'balancing'.

Most of the Roadcraft section on cornering deals with cornering with restricted vision, where the point at which the speed should be lowest is just before corner entry. In this scenario, Roadcraft teaching is to go back on the gas gently just before turn in, to maintain speed while the distance you can see remains constant, and then to increase the gas to accelerate to a suitable pace for the next section of road as you approach the end of the corner and the distance you can see extends (in Roadcraft speak 'the limit point starts to move away more quickly'). Both my IAM and Rospa examiners have called the use of gas in the corner in this way: 'balancing the car with the accelerator'.

Do you agree with this terminology? Do you teach students to corner in this style even where there is open vision through a corner? Planning to get back on the gas just before turn in makes sure that your entry speed is low enough, and it is a comfortable style of cornering for passengers, but it contrasts with the race technique of turning in off the gas and perhaps under trail braking.


Cornering is something I'm going to cover in some future posts. I initially wanted to get across the importance of smooth car control in high performance road driving and get people thinking about how they transfer the vehicles weight around. Balancing a car on the throttle whilst cornering is something I'll cover in the future, I promise!

sclayto2

963 posts

208 months

Wednesday 7th March 2007
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As a driver and a rider, I have to say that all this makes a great deal of sense for both types of vehicle.

Well put.

freddytin

1,184 posts

226 months

Wednesday 7th March 2007
quotequote all
Another good read.
I was wondering if anyone has come across driving aids to help drivers learn the art of balancing the car ?

I was thinking along the lines of a simple dash mounted pendulum acting as a G meter.

Failing this, it's going to be a test track ,or a bike. Better still....both .

R_U_LOCAL

Original Poster:

2,676 posts

207 months

Wednesday 7th March 2007
quotequote all
freddytin said:
Another good read.
I was wondering if anyone has come across driving aids to help drivers learn the art of balancing the car ?

I was thinking along the lines of a simple dash mounted pendulum acting as a G meter.

Failing this, it's going to be a test track ,or a bike. Better still....both .


Jackie Stewart used to teach using a big shallow bowl-type-thing attached to a cars bonnet with a tennis ball in it. He used to teach people to drive around a racing circuit without the ball coming out of the bowl. I thought it was a very nice teaching aid.

Or you could drive round with a bowl of water on your knee and try to stay dry.

Whilst I'm on the subject of Jackie Stewart, although I'm of the view that a lot of track techniques should stay on the track, I am a big admirer of Sir Jackie. He has always maintained that good driving is based around a smooth driving style, and he has some very nice ways of teaching the principles of smooth driving and vehicle balance.

If any of you saw the episode of Top Gear when he taught James May how to improve his lap times around Oulton Park, there was a nice example when they were having a mid-session break. Jackie pushed May and he stumbled off balance, and then he leaned against him, pushing him just as hard, but building up gradually, and May tensed against him and didn't lose his balance.

Jackie's point was that if you sneak up on a car with an unexpected move, it'll go off-balance, but if you build up gradually into a move, the car becomes ready for it, and keeps its balance.

It was a nice visual example, and it's one I now use myself.

freddytin

1,184 posts

226 months

Wednesday 7th March 2007
quotequote all
R_U_LOCAL said:
freddytin said:
Another good read.
I was wondering if anyone has come across driving aids to help drivers learn the art of balancing the car ?

I was thinking along the lines of a simple dash mounted pendulum acting as a G meter.

Failing this, it's going to be a test track ,or a bike. Better still....both .


Jackie Stewart used to teach using a big shallow bowl-type-thing attached to a cars bonnet with a tennis ball in it. He used to teach people to drive around a racing circuit without the ball coming out of the bowl. I thought it was a very nice teaching aid.

Or you could drive round with a bowl of water on your knee and try to stay dry.

Whilst I'm on the subject of Jackie Stewart, although I'm of the view that a lot of track techniques should stay on the track, I am a big admirer of Sir Jackie. He has always maintained that good driving is based around a smooth driving style, and he has some very nice ways of teaching the principles of smooth driving and vehicle balance.

If any of you saw the episode of Top Gear when he taught James May how to improve his lap times around Oulton Park, there was a nice example when they were having a mid-session break. Jackie pushed May and he stumbled off balance, and then he leaned against him, pushing him just as hard, but building up gradually, and May tensed against him and didn't lose his balance.

Jackie's point was that if you sneak up on a car with an unexpected move, it'll go off-balance, but if you build up gradually into a move, the car becomes ready for it, and keeps its balance.

It was a nice visual example, and it's one I now use myself.


Thanks again for another top tip. I'll use the water idea, a bottle within a bottle, with holes drilled around the inner one at a set level to allow spilliage into the outer vessel when the vehicle is being thrown out of balance.

Flat in Fifth

43,960 posts

250 months

Friday 6th April 2007
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Not able to add much to Reg's excellent articles, really enjoying reading them. thumbup

Just going to add on this question of balance, interesting that Beemers are now set in understeering mode. scratchchin

This is basically how I used to set my rwd rally cars up, others thought I was barmy, but to me it made it able to drive in a much smoother balanced way, more time spent going rather than fighting an oversteering monster.

And as you can see from my profile pic it still allowed nice deliberately sideways controlled entry into bends. hehe

On the other hand when that pic was taken it had just been re-shelled! paperbag

.... :ahem: - moving on. hehe

StressedDave

839 posts

261 months

Friday 6th April 2007
quotequote all
At the risk of upsetting Reg with more science laugh, one of the reasons that all road cars are engineered to understeer is that they respond quicker to a steering input than a car set up to be neutral or oversteer. Sure, you need more steering to get around the same bend as the speed increases but the time it takes to get to the steady cornering position is less.

With a RWD car you want a little bit of understeer in any case as that means that the front tyres run out of grip first. On a circuit (or when rallying) that means that when you're cornering at the limit of grip, you still have a little in reserve to enable you to accelerate out of a corner and make better progress. If you set up the car to oversteer the rears have run out of grip first and you can't actually accelerate away...

flemke

22,863 posts

236 months

Saturday 7th April 2007
quotequote all
R_U_LOCAL said:
freddytin said:
Another good read.
I was wondering if anyone has come across driving aids to help drivers learn the art of balancing the car ?

I was thinking along the lines of a simple dash mounted pendulum acting as a G meter.

Failing this, it's going to be a test track ,or a bike. Better still....both .


Jackie Stewart used to teach using a big shallow bowl-type-thing attached to a cars bonnet with a tennis ball in it. He used to teach people to drive around a racing circuit without the ball coming out of the bowl. I thought it was a very nice teaching aid.

Or you could drive round with a bowl of water on your knee and try to stay dry.

Whilst I'm on the subject of Jackie Stewart, although I'm of the view that a lot of track techniques should stay on the track, I am a big admirer of Sir Jackie. He has always maintained that good driving is based around a smooth driving style, and he has some very nice ways of teaching the principles of smooth driving and vehicle balance.

If any of you saw the episode of Top Gear when he taught James May how to improve his lap times around Oulton Park, there was a nice example when they were having a mid-session break. Jackie pushed May and he stumbled off balance, and then he leaned against him, pushing him just as hard, but building up gradually, and May tensed against him and didn't lose his balance.

Jackie's point was that if you sneak up on a car with an unexpected move, it'll go off-balance, but if you build up gradually into a move, the car becomes ready for it, and keeps its balance.

It was a nice visual example, and it's one I now use myself.

A couple of other road car-related anecdotes about Stewart:

- Stewart advocates pinching the steering wheel between thumb and forefinger, with part of the palm in contact for comfort but not doing the work. With this technique, feedback and control are concentrated in the most sensitive places.
It takes some getting used to, but it is better.

- Juan Pablo Montoya related this story in an interview three-four years ago.
This occured during the time when Montoya was at his most successful at Williams, leading and winning GPs.

It seems that for whatever reason Montoya and Stewart were the star attractions at some corporate day at a British race circuit. The idea was that they would drive guests around the circuit in a modern road car, but first they were asked to do timed laps in the car together, each riding as the other's passenger.
Stewart drove first. On his hot laps, Montoya said, Stewart seemed to be taking his time, shifting gear in a relaxed way and taking nothing to the edge. Montoya said that, as he observed this display, he actually felt sorry for Stewart, thinking that it was a bit sad that this former world champion's ability to drive at the limit had so deteriorated through the years.
After Stewart had completed his laps it was Montoya's turn. Montoya thought that he had a little something to prove to Stewart (racers being racers), so he went balls-out. He said that he drove as hard as he could, ramming home the gearchanges, giving no quarter into and out of the bends, using the throttle and brakes heavily. Ultimately Montoya pushed that road car as quickly as he knew how to do.
After Montoya had finished his laps, he was rather surprised to learn that his fastest lap had been 8/10s of a second slower than Stewart's.

scoobman

450 posts

204 months

Monday 16th April 2007
quotequote all
Understeer is better for the road? As a default set up.
Well I think so.
I had a good discusion with Simon DB on Scoobynet a few years back about this.

My view was that.
RWD - Oversteering cars. Can be alot more fun and most certainly I can see the apeal for the track. They are more ´´matcho´´ the big powerful RWD car that takes real skill to control. They feature in glossy magazines with Clarkson going sideways and perhaps provide a more ´´pure´´ driving experience......

....right enough of all that old stuff. Back down to earth back to reality. A wet A road in Wales on a Tuesday morning and you have to make progress as quickly but as safely as possible.

These are the kind of roads we actually find ourselves on. Not an airfield.

So given that the car is driven correctly. Slow in fast out - No trail lifting or braking.

The key is how progressively and predictably grip is lost. The reason why I like properly set up subarus so much.....
Is that the loss of grip is PROGRESSIVE
The loss of grip is very PREDICTABLE
One without DCCD - Standard 50-50 Front Rear Split. Will understeer on the limits of its grip in a very predictable and progressive way. A few slight stearing inputs and feathering of the throttle and we are on our way again
I feel that the understeer thing is far more easier to sort out in the real world and also tends to take up far less road space. I dont want a RWD car oversteering like a goodun when a stone wall is one side and a row nice solid trees is on the other.

So, It may be boring, but an Understeering set up for the road is the thing for me. UR Quattro, Scooby style.

Obviously on a track with lots of space to play, then Oversteer gets my vote.
Driving purists snear at Understeer but I do feel it has its place.

Interested to hear that BMW are now engineering understeer into cars. I heard about Porsche begining to do this a while back.