Using gears to slow

[f3racer]

I understand the IAM principle in its basic form is "gears to go and brakes to slow".

I always deliberately try to avoid the use of brakes for ecomomic purposes and reduce sleed using the gears where possible. The exception is the gentlest of pressure on the brake pedal, just to display my brake lights.

I've never come unstuck by doing this. I've never had to replace a clutch or gearbox, and my care does a lot more miles between brake pads being replaced than most!

Is the IAM's justification for slowing down entirely using the brakes and then making a single gearchange really valid?

[ScoobyChris]

Is the IAM's justification for slowing down entirely using the brakes and then making a single gearchange really valid?

I'm not sure what the IAM's justification is, but the System of car control says that before taking the gear, you must be at the correct speed (and doesn't dictate how you get there). If you're looking to make maximum progress, as encouraged by the IAM/RoSPA et al, you'll be wanting to use the brakes to have the shortest braking phase, and also most stable as the braking is acting on all 4 wheels. If you don't care about making progress, then the main priority is that cars around know what you're doing and it's in line with their expectations.

Chris

[Gareth]

I always deliberately try to avoid the use of brakes for ecomomic purposes and reduce sleed using the gears where possible.

You don't seem to have thought it through.

First the cost of the parts. For most cars the cost of replacing brake friction material, (pads or shoes), is small compared to the cost of replacing the clutch. This is the case even when the brake discs or drums need replacing from time to time. The equation moves even further in favour of using brakes when you consider the cost of replacing dual mass flywheels.

From a control point of view you are choosing a relatively complex sequence - repeated gear changes - over the relatively simple steps of braking to a suitably slow speed then making a single gear change. Assuming you can do good gear changes - perfectly matching engine speed to road speed - then all you're doing is handling the complex sequence more competently than most drivers. This is all pretty pointless if your aim is to teach a method to people who either don't like driving or are merely appliance operators.

Next, whatever method you use to slow down the 'wasted' fuel is that needed to subsequently accelerate, so using gears is effectively no different to using brakes in this. If you wanted to be the most economic you'd try to slow down as slowly as possible, possibly using neither brakes nor gears but just lifting off the accelerator. You'd probably need to work out whether it is better to keep it in gear with the clutch up, (normally shuts off the fuel), or depress the clutch to minimise friction losses, but neither approach is anywhere close to the aims of UK advanced driving.

In case you missed it, the aims of Roadcraft based advanced driving in the UK could be restated as being to give drivers the skill and experience needed to arrive safely when they are under time pressure. This means they need to be able to maximise progress while keeping to traffic laws.

[martine]

I always deliberately try to avoid the use of brakes for ecomomic purposes and reduce sleed using the gears where possible.

So when you're slowing and dip the clutch and go from 4th to 3rd to 2nd, you are using more fuel than keeping it in 4th, clutch up and using the brakes. This is because modern engines have a fuel cutoff in this situation i.e.no fuel is being used. As soon as you put the clutch down to change gear, fuel has to be used to keep the engine going.

Other more important (in my view) justifications include:
* keeping both hands on the wheel for longer (safety and more accurate steering)
* more balanced (4 wheels are braking, if you use gears to slow only 2 (unless it's 4wd)
* easier to adjust rate of slowing precisely

Makes sense to me.

[Ralge]

I always deliberately try to avoid the use of brakes for ecomomic purposes and reduce sleed using the gears where possible.

So when you're slowing and dip the clutch and go from 4th to 3rd to 2nd, you are using more fuel than keeping it in 4th, clutch up and using the brakes. This is because modern engines have a fuel cutoff in this situation i.e.no fuel is being used. As soon as you put the clutch down to change gear, fuel has to be used to keep the engine going.

Other more important (in my view) justifications include:
* keeping both hands on the wheel for longer (safety and more accurate steering)
* more balanced (4 wheels are braking, if you use gears to slow only 2 (unless it's 4wd)
* easier to adjust rate of slowing precisely

Makes sense to me.

And it's been put to me that assessing the hazard accurately, slowing smoothly by acceleration sense and braking whilst delaying a gear change until you know what gear will take you through the hazard represents a level of finesse that an Advanced Driver should aspire to.
It's in this context that unnecessary, intermediate gear changes are thought of as less than perfect if they represent an inaccurate assessment of the hazard.

[daz6215]

Next, whatever method you use to slow down the 'wasted' fuel is that needed to subsequently accelerate, so using gears is effectively no different to using brakes in this. If you wanted to be the most economic you'd try to slow down as slowly as possible, possibly using neither brakes nor gears but just lifting off the accelerator. You'd probably need to work out whether it is better to keep it in gear with the clutch up, (normally shuts off the fuel), or depress the clutch to minimise friction losses, but neither approach is anywhere close to the aims of UK advanced driving.

.

Isn't slowing down by lifting off and not using the brakes 'acceleration sense' as advocated by Roadcraft? It does actually require a lifted vision and good anticipation to achieve successfully, which is all part of advanced driving.

[Gareth]

Isn't slowing down by lifting off and not using the brakes 'acceleration sense' as advocated by Roadcraft? It does actually require a lifted vision and good anticipation to achieve successfully, which is all part of advanced driving.

Lifting off, slowing for lower speed limits apart, is a subtle application rather than the main method of slowing down. Excessively slow slowing is what some people mistakenly mistake for smoothness but denies the aim of sustained good progress.

[daz6215]

Isn't slowing down by lifting off and not using the brakes 'acceleration sense' as advocated by Roadcraft? It does actually require a lifted vision and good anticipation to achieve successfully, which is all part of advanced driving.

Lifting off, slowing for lower speed limits apart, is a subtle application rather than the main method of slowing down. Excessively slow slowing is what some people mistakenly mistake for smoothness but denies the aim of sustained good progress.

Depends on the definition of 'progress'!

Slow to Flow and all that!

[GJD]

Isn't slowing down by lifting off and not using the brakes 'acceleration sense' as advocated by Roadcraft?

Lifting off, slowing for lower speed limits apart, is a subtle application rather than the main method of slowing down. Excessively slow slowing is what some people mistakenly mistake for smoothness but denies the aim of sustained good progress.

Depends on the definition of 'progress'!

Slow to Flow and all that!

Roadcraft says "Acceleration sense helps you avoid unnecessary braking" [my italics]. It gives two examples: accelerating out of a junction only to have to brake for traffic ahead, and accelerating up behind a slower vehicle and having to brake before overtaking. I don't think Roadcraft advocates trying to generally avoid the brakes. Indeed, four pages after the acceleration sense bit, it says "Use the brakes when you need to make more than a gradual adjustment to your road speed."

The no brakes game is a good exercise for getting your vision up and planning ahead, but I wouldn't drive like that all the time. By permitting myself to incorporate more than just gradual adjustments to road speed in my plan, I think I improve both progress and flow.

[daz6215]

Roadcraft says "Acceleration sense helps you avoid unnecessary braking" [my italics]. It gives two examples: accelerating out of a junction only to have to brake for traffic ahead, and accelerating up behind a slower vehicle and having to brake before overtaking. I don't think Roadcraft advocates trying to generally avoid the brakes. Indeed, four pages after the acceleration sense bit, it says "Use the brakes when you need to make more than a gradual adjustment to your road speed."

The no brakes game is a good exercise for getting your vision up and planning ahead, but I wouldn't drive like that all the time. By permitting myself to incorporate more than just gradual adjustments to road speed in my plan, I think I improve both progress and flow.

It also says "Acceleration sense is the ability to vary the vehicle speed by accurate use of the accelerator to meet changing road and traffic conditions" There's no point barreling into a hazard if there is no where to go! time it right and you may arrive at that point when its cleared, be it by using the brakes or acceleration sense, they are both advocated!

[7db]

The brake is the biggest control in your car - twice the oomph of the accelerator, and easily as much as the wheel. Why wouldn't you use it?

Good braking leads to good hazard management, leads to early acceleration, leads to good progress.

[Gareth]

time it right and you may arrive at that point when its cleared, be it by using the brakes or acceleration sense, they are both advocated!

Both of which are far from the method advocated by the OP.

[daz6215]

time it right and you may arrive at that point when its cleared, be it by using the brakes or acceleration sense, they are both advocated!

Both of which are far from the method advocated by the OP.

Maybe I misinterpreted your explanation, It looked like you described acceleration sense in your answer to the OP and then said neither were advocated in advanced driving!

[Gareth]

Maybe I misinterpreted your explanation, It looked like you described acceleration sense in your answer to the OP and then said neither were advocated in advanced driving!

I probably wasn't clear enough in what I wrote.

The OP appears to want to cheapen the cost of motoring and suggests using gears to slow is a great way of going about it. In the part of my reply you picked up on I was pointing out that greater fuel savings can be had by using neither brakes nor gears to slow down, instead as much as possible using friction losses and drag to slow down as slowly as possible.

[The reason this saves fuel is that when you prolong slowing down then you haven't used fuel to needlessly maintain your speed prior to normal slowing down.]

I was attempting to point out there is a cross-over point as the engine speed drops where the fuel cut-off stops being so effective, and a decision would need to be made about whether to continue slowing with the drive train engaged or disengaged.

The point I was also attempting to make was the driving in this way -- attempting to slow down as slowly as possible -- is outside the scope of Roadcraft-based advanced driving.

[f3racer]

I'm not sure the engine is using any extra fule by being used to slow the car down, providing no throttle is being applied. Fair point regarding good progress though. I suppose my technique is good for steadily pottering around and trying to preseve consumables such as brake pads as much as possible. Maybe a switch to using the brakes alone when going for it on the open road subsequently makes sense.