Critical Analysis

[michael769]

In the System why does Position come before Speed?

Speed is determined by vision. Vision is determined by position. Geometry, innit.

Position also determines the available space around you which influences the appropriate speed.

[Horse]

In the System why does Position come before Speed?

Speed is determined by vision. Vision is determined by position.

And position is, initially, determined by safety. Surprising number of people forget this, increasing their view by reducing safety margins.

[hir]

...the method I prefer is to turn in under braking to settle the car down and then release the brake prior to driving around the radius.

Thoughts?

How are you defining a "settled" car?

My understanding is that a car is settled when it is neither under acceleration nor braking; when the weight is neither at the front (braking) or at the rear (acceleration) but is evenly distributed, ie. the car is "settled".

This is usually achieved during that very brief moment between coming off the brakes and lifting the clutch to engage the new gear - assuming we have good brake/gear separation. The car is then nicely settled before power is re-applied.

[fungus]

I tend to enter a bend under a light throttle and start to increase acceleration as the bend opens and straightens out, or as Jackie Stewart told James May, "Do not accelerate to gain speed until you can see that you can contineu to accelerate".

Position for a left hand bend. When in free flowing traffic but following others, the best view would be obtained from a position to the left, not towards the centre, especially if others are driving in a wider position. Although the accepted position for a left hand bend is towards the centre, the inexperienced might hold this position in the face of oncoming traffic.

Agreed Fungus, so based on that, what advice would you give to the student ?

On approach, assess the sharpness of the bend using the limit point and adjust your speed so as to be able to stop within the remaining distance, half that on a single track road. Note the presence and position of oncoming vehicles and take up a safety line ie. no approaching vehicles just left of centre, if there are approaching vehicles present, in centre of your lane. If following other vehicles, take up a position slightly more to the left if it would be beneficial and necessary to gain a slight increase in vision. Once the correct speed is achieved and the correct gear engaged, apply light throttle to maintain speed only as you enter the bend. Do not accelerate to gain speed until the bend starts straightening out, then apply enough power to increase speed according to the straightening of the bend. You should be able to feel the front of the car lifting very slightly as you smoothly increase acceleration, and then more as you exit the bend.

I would not advise a learner to take up a position well to the right of their lane which could put them on a collision course with an oncoming vehicle, especially a biker positioning too far to the right leaning into the bend with their head over the centre line. Many experienced drivers do not give thought to their position, so although some learners might be perfectly capable of safely assessing the risks, I would advise them to keep to the centre of their lane for safety.

[7db]

If you get the student to look in the right place, the position will sort itself out.

If you get them to apply positive power throughout the middle phase of the corner then will then get their entry speeds down after scaring themselves a few times. Positive power, because it's all too easy to take a trailing throttle and imagine you are "on the gas".

[Horse]

How are you defining a "settled" car?

My understanding is that a car is settled when it is neither under acceleration nor braking; when the weight is neither at the front (braking) or at the rear (acceleration) but is evenly distributed, ie. the car is "settled".

This is usually achieved during that very brief moment between coming off the brakes and lifting the clutch to engage the new gear The car is then nicely settled before power is re-applied.

If it's not under enough power to balance the rolling resistance of tyres, brakes rubbing, bearings, etc., isn't that braking?

[daz6215]

I was recently reading a post by Rob on piston heads where he makes a statement "If you put something on, take something off" I am personally in agreement with this as it does tend to balance the vehicle, would this be of any value to Roadcraft?

[Horse]

I was recently reading a post by Rob on piston heads where he makes a statement "If you put something on, take something off" I am personally in agreement with this as it does tend to balance the vehicle, would this be of any value to Roadcraft?

Like . . . Braking a motorcycle mid-corner, "Lean = less" ?

[Less snappy, greater lean = reduced braking effort ]

[hir]

How are you defining a "settled" car?

My understanding is that a car is settled when it is neither under acceleration nor braking; when the weight is neither at the front (braking) or at the rear (acceleration) but is evenly distributed, ie. the car is "settled".

This is usually achieved during that very brief moment between coming off the brakes and lifting the clutch to engage the new gear The car is then nicely settled before power is re-applied.

If it's not under enough power to balance the rolling resistance of tyres, brakes rubbing, bearings, etc., isn't that braking?

I understand where you're coming from but, at this level of physics we tend to describe the car as being either "settled or "unsettled". I'm not sure that friction caused by the rolling resistance of tyres [in a straight line] or the friction caused by bearings would be sufficient to "unsettle" the car; hence my suggestion that the car would be "settled" during the phase described above.

Not too sure why the brakes would be rubbing, unless they were poorly maintained.

[Gareth]

I understand where you're coming from but, at this level of physics we tend to describe the car as being either "settled or "unsettled".

We sometimes use 'settled' to mean under positive control - for example when returning to the accelerator after braking, because it can take a small amount of time after applying the acceleration for the car to 'react' to what the driver is telling it to do, (or slightly more accurately, for the natural springiness of the car suspension to settle to the newly applied weight distribution, if you see what I mean).

[waremark]

In the System why does Position come before Speed?

Speed is determined by vision. Vision is determined by position. Geometry, innit.

Position also determines the available space around you which influences the appropriate speed.

Well I am sorry no-one else thinks this is an interesting aspect of Roadcraft to challenge. I don't in any way disagree with the conventional wisdom on position, which I practise and 'teach': to prioritise safety, then vision, then stability, in that order. Personally, if I am approaching at high speed a feature for which I need to lose a lot of speed, I will have considered my course before starting to slow, but I will often have applied the brakes before moving to the relevant position. Accordingly I think it should be I-CSGA.

[waremark]

No the car isn't destabilised on approach but if the corner is read incorrectly and entered to quick the abrubt change in direction without easing off slightly and or applying the brakes can cause unwanted lateral force.

One of the main advantages of completing the braking before entry to the hazard is that if the driver has misjudged and not braked enough he has time and space in hand to continue braking. Thus he is far less likely to enter the hazard too quickly. If you plan to brake into the corner there is less reserve of safety.

[waremark]

I was recently reading a post by Rob on piston heads where he makes a statement "If you put something on, take something off" I am personally in agreement with this as it does tend to balance the vehicle, would this be of any value to Roadcraft?

Rob has posted on this extensively in the past. He comes from a racing background (and is an excellent road driver - I went out with him).

His argument is for braking into the bend, blending off the brakes as you progressively apply steering, and blending on the power as you progressively reduce steering towards the exit of the bend (but not before you reduce steering). He changes down under braking using H & T. Taking a bend like this, the tyres are handling a roughly constant g loading throughout.

On the other hand if you drive like a Roadcrafter the tyres are under load while braking, then the load is reduced as you come off the brakes before turn-in, then there is a turning load, then when the view opens up you start to accelerate while there is still a turning load, and you increase the load on the tyres further by accelerating while still turning.

Personally I prefer the Roadcraft approach. I would say that the grip of the tyres should not be an issue and that other matters such as vision and safety margins are more significant than maintaining a constant load. Rob points out that many drivers including 'advanced drivers' are often much closer to the limit of grip than they realise, and that therefore it would be valuable to drive in a style which keeps the margin from the limit of grip constant so as not to inadvertanly step over it.

[daz6215]

So does Rob have a valid argument?

[hir]

We sometimes use 'settled' to mean under positive control - for example when returning to the accelerator after braking, because it can take a small amount of time after applying the acceleration for the car to 'react' to what the driver is telling it to do, (or slightly more accurately, for the natural springiness of the car suspension to settle to the newly applied weight distribution, if you see what I mean).

Can you clarify "under positive control", please? Is "settled" before or after the car reacts to what the driver is telling it to do?

I'm assuming you're referring to the moment just after the car reacts to the accelerator and, I also assume that the power that is applied in order to maintain a "settled" car is just sufficient to maintain a constant speed, neither decelerating nor accelerating.

Have I assumed correctly or, have I completely misunderstood?