Changing down through gears when slowing down.

[Goochie]

What does 4th gear buy you?

Chris

Lots of nice noise and a feeling of increased confidence as I the car feels like its slowing itself down ratehr than just slowing because I'm braking.

But this is probably because its as I've always driven - will try it differently this evening.

[SteVRs]

I believe on overrun the fuel supply is cut.

[TeflonTom]

I believe on overrun the fuel supply is cut.

no not or road cars, but yes on many race cars this is true, if the fuel cut on overrun it would burble and pop back!

Diesels have less engine braking!!!!!!!

diesel engines have a far higher mechanical compression ratio so the engine braking will be more!

i allways shift down through the box when decelerating from motorway speeds because it's kinder on the brakes and because of the braking effect of the engine your less likely to skid iff it's a slippery surface. but if driving more slowly it's not worth downshifting! and as for fuel economy, it makes virtually no difference at all!

[ScoobyChris]

diesel engines have a far higher mechanical compression ratio so the engine braking will be more!

That's not my experience with modern diesels, and it seems I'm not alone

http://www.bankspower.com/tech_howexhaustbrakeworks.cfm

Chris

[TeflonTom]

That's not my experience with modern diesels' date=' and it seems I'm not alone

Chris[/quote']

that might be a trait of turbocharging

[ScoobyChris]

that might be a trait of turbocharging

Possibly, although my old 300 TDI Disco had loads of engine braking.

Chris

[WoodieGuthrie]

I always use the gearbox when slowing down-much more effective in my opinion-and a good habit to get into if your brakes fail!

need to get heel and toe down pat now....

[KenONeill]

I'm another one that "block shifts" when I'm getting near to the speed I'm likely to be able to pull away again from, and uses engine braking to basically control the road speed downhill.

With the trip computer in "instantaneous mpg" mode, it becomes clear that, doing this, the VAG diesels use minimal to no fuel, as long as you shift by about 1_000 rpm, and frankly I'd not want to rev the engine much lower unless stuck in a traffic queue, when the ability to run at idle revs right up to 4th gear (maybe even 5th in a Furbie D?) comes into its own.

The throttle and gears are there to control your rate of increase of speed, the brakes to reduce it!

[Silk]

Some of you may have read the DSG thread in the New Octavia section that is in danger of going off topic. What it comes down to is this.......

Do you change down through the 'box when slowing down?

Itr's now accepted practice to use brakes to slow to required speed and select appropriate gear to continue. I've lost count of the times I've done this argument to death on the internet.

I teach Advanced Driving for the IAM and I've never met anyone who has reverted back after mastering the "correct" way.

The trouble is, driving can not be done as a correspondence course, it needs practical demonstration.

To put it simply, there are absolutely no advantages to going down through the gears when slowing in normal road driving.

[Chris GB]

He he this old chestnut again!

So where to begin? Coasting? Knocking it into neutral approaching and braking has three disadvantages:

1: You use more fuel as the overrun cut off is not triggered

2: You lose the effectiveness of your brake servo if in a petrol car

3: No 2 can become a real problem if you need to stop suddenly

Changing down while slowing. Well the IAM / RoSPA way is best in most situations. The key is to break your approach down into phases. However, there are times when the decision as to what speed and gear you need cannot be made, but balancing probabilities, it may be third, or you may be stopping. This is where I dont quite get the IAM / RoSPA method. Surely an intermediate gear in these circumstnaces is preferable to coasting or under revving the engine? Will review this when I get back to advanced driving. Never resolved it when I was with the IAM previously. Never failed a test for it either though.

Using the gears to slow down? Who said they would rather use the engine to slow if too fast into a corner? Jeeezus! Engine braking will only be applied to the driven wheels, thus pushing them closer to the limit of adhesion than if the force were shared across all four wheels. Generally, engine braking is OK when using it to control speed on a gradient, but is not as accurate and effective as using the brakes if reducing speed for a specific hazard.

Now the dangerous knock on effects of changing down to slow down are not mechanical, but driver behaviour related. If you get into the habit of changing down to slow down, how long will it be before the habit develops further and you often slow down using gears only? Be honest, some of you may already be doing it. And do your brake lights come on when slowing down on the gears only?

Lastly, race track use of the gears. If you have a sequential gearbox, fading or marginal brakes or have bias set up to engine brake, then downshifting one gear at a time is OK, however, the fastest way is to use the block change when you can. It gives you the maximum stability under braking. Even the very best drivers are not able to heel and toe so accurately as to better the distribution of force on a well set up braking system. Take a look at the modern race bike. They have slipper clutches to avoid locking the rear wheel on the downchange.

Simple really, gears to go brakes to slow.

Chris

[ScoobyChris]

This is where I dont quite get the IAM / RoSPA method. Surely an intermediate gear in these circumstnaces is preferable to coasting or under revving the engine? Will review this when I get back to advanced driving. Never resolved it when I was with the IAM previously. Never failed a test for it either though.

The system is designed to be flexible so yes, an intermediate gear is acceptable if you would be coasting or underrevving in the current gear you're in I believe the way it's argued as still using the system, is that the approach is broken down into 2 hazards, but I'd need to dig around to find the theory behind that

Chris

[bus driver]

hi people,

i learned to drive 20 years ago, and was taught to use both the gears and the brakes to slow down. my girlfriend who is learning to drive now, does not use the gears to slow down, which scares me, and has caused some riots in the car. I spoke to her driving instructor and he said i was right the way i was driving, and Lucie was right the way she was driving, so who's right ?

[Chris GB]

The system is designed to be flexible so yes' date=' an intermediate gear is acceptable if you would be coasting or underrevving in the current gear you're in I believe the way it's argued as still using the system, is that the approach is broken down into 2 hazards, but I'd need to dig around to find the theory behind that

Chris[/quote']

Yep, that would be it. Observer I had years ago really was a "one shot" stalwart even when it really was not suitable for the situation.

Chris

[Chris GB]

hi people' date='

i learned to drive 20 years ago, and was taught to use both the gears and the brakes to slow down. my girlfriend who is learning to drive now, does not use the gears to slow down, which scares me, and has caused some riots in the car. I spoke to her driving instructor and he said i was right the way i was driving, and Lucie was right the way she was driving, so who's right ?[/quote']

Not a case of right or wrong, more of which method is most suitable. Slowing down on engine and brakes is not wrong until you start using all engine braking, at which point you stop giving a signal to the following cars.

Distribution of braking forces is best if just braking in whatever gear you were in, then changing down. There may be wear issues if using downchages to slow throughout the life of the car, but maybe not.

You would get away with it on a driving test until it was deemed that an unnecessary gear change had adversley or potentially adversely affected your control of the car.

Chris

[Goochie]

I'm thinking that I need to find the time to continue my IAM

[ScoobyChris]

I'm thinking that I need to find the time to continue my IAM

Might help to preserve the delicate gearbox in the Z too

Chris

[ncarring]

Well I've voted yes. I always have changed down through the gears as that's how I was taught, and it seems pointless to waste engine braking when you have it available, to me. Particularly on track I find it useful to keep the car balanced - you have to absolutely stamp on the brakes anyway, and rather than do more of that, I tend to change down a gear or two on the approach to a corner before braking right up to just before the turn-in point. That said I was out with an instructor at Castle Combe the other day and he persuaded me braking slightly earlier gave more balance, so I'm still learning.

On the road, I use a combination of both techniques. Yes, when all you're concerned with is driving smoothly and ultra safely, the IaM etc. method is appropriate. When you want to make some more rapid progress, I still find more use of the gears helps keep the car balanced. Just my preference.

I've never learned to heel and toe properly, so tend to go on and off the brakes blipping the throttle for the down changes. The next logical step is to learn to heel and toe so the braking can be continuous, but each car you drive responds slightly differently, so it's a tough thing to learn unless you're driving the same car, fast, every day.

The one thing I don't do, since a rather acid comment from my Dad when I was learning, is use the clutch as a brake. Being in a car with someone who does that really makes my teeth grate nowadays, too, so I understand what he meant.

[DangerMouse]

If I'm approaching a very tight bend' date=' I will brake down to an appropriate speed before the start of the bend and select an appropriate gear to accelerate through the bend If it's a technique recommended by police class 1 drivers and other advanced driving organisations, it's good enough for me

Chris[/quote']

Makes sense to me too. That's what I do as per all my driving lessons from my original instructor when I was learning and from the old bill.

Changing gear going round a bend is just as bad as braking, so either way you need to do one or the other before reaching the bend - might as well be breaking as that's waht breaks are for! Engines make you move, brakes make you stop... That's my take

[LittlePaul]

No - I slow with the brakes and then change to a gear that's appropriate to the speed...as taught by a Police Class 1 driver.

The main reason though is that brakes are cheap to replace and a gearbox isn't - the original reason for using the gears to slow down was the poor brakes on old cars' date=' not applicable any more.[/quote']

Absolutely, that's what Ive always done, and for that exact reason.

However, as was pointed out to me, the vRS and similar fast cars hvae gearboxes designed to do it, so woudlnt brake from that.

Interesting to hear if that's right tho...?

[gilesk]

My dad would say 'Why use up your brake pads and wear the gear box' date=' that's what bumpers are for.'

Seriously though, I just knock it into neutral and brake as and if I need to.[/quote']

That is very very dangerous as you have little control over the car

[faboka vrs]

However' date=' as was pointed out to me, the vRS and similar fast cars hvae gearboxes designed to do it, so woudlnt brake from that.

[/quote']

How are the gearboxes designed to do it? Ok a gearbox might be strong but doesnt been its designed to do it becuase its in a fast car. I'm sure you will have a very similar gear to say one fitted to a 1.8T 150bhp passet or Superb. Now due to its weight I dont think it'll be classed as a "fast" car.

I think its very simple. More you use your box the more wear it has on it. It WILL break at some stage but depending how you use it will depend on how long it'll last.

[Goochie]

I think its very simple. More you use your box the more wear it has on it. It WILL break at some stage but depending how you use it will depend on how long it'll last.

If your car has a "Z" logo on the boot then it may break before you'd resonably expect it to

[TeflonTom]

I think its very simple. More you use your box the more wear it has on it. It WILL break at some stage but depending how you use it will depend on how long it'll last.

yeah but it's better than underevving the engine by leaving it in gear and braking. besides if the gearbox is turning faster it puts less load on the bearings.

[ScoobyChris]

yeah but it's better than underevving the engine by leaving it in gear and braking.

Who said anything about underrevving?

Chris

[TeflonTom]

Who said anything about underrevving?

Chris

i dunno, i think i read it somwhere in at the begining of this thread somwhere! or have i just trolled again??