Is there a reason why I shouldn't coast

Whiplashy · 29-12-2017 07:43PM #1

I remember years back when I was learning to drive, my instructor was always giving out about me coasting. I never really understood what he was on about though. Driving this evening a passenger pointed out that I coast every time I come up to a junction. It's how I've always driven, and I'm not too sure I'd actually be able to stop doing it. I press the clutch approaching the junction, keep it pressed while I'm going down through the gears and braking. I probably start clutching about 3 or 4 car lengths before I need to stop. Is there an actual reason why I shouldn't be doing it? The passenger today didn't know why, just that I shouldn't.

dudara · 29-12-2017 07:46PM

It essentially means that you have less control over the car as you’ve disengaged the engine by depressing the clutch.

Alkers · 29-12-2017 07:48PM

And why do you go down through the gears if you have the clutch depressed the whole time?

Toyotafanboi · 29-12-2017 07:48PM

Staying in gear while slowing down in a modern car will save you fuel over coasting in neutral while braking too.

Dakota Dan · 29-12-2017 07:48PM

Whiplashy wrote: »

I remember years back when I was learning to drive, my instructor was always giving out about me coasting. I never really understood what he was on about though. Driving this evening a passenger pointed out that I coast every time I come up to a junction. It's how I've always driven, and I'm not too sure I'd actually be able to stop doing it. I press the clutch approaching the junction, keep it pressed while I'm going down through the gears and braking. I probably start clutching about 3 or 4 car lengths before I need to stop. Is there an actual reason why I shouldn't be doing it? The passenger today didn't know why, just that I shouldn't.

Ask the passenger if they would like to walk instead

Whiplashy · 29-12-2017 07:49PM

Something I need to work on so! Thanks very much

km991148 · 29-12-2017 07:50PM

Was about to say the same (less control)
Also - what exactly do you mean by "while I'm going down through the gears" - to me that sounds like you are selecting gears on the way down (4-2-1 for example) with the clutch depressed the whole time (Which would be pointless..)

OldMrBrennan83 · 29-12-2017 07:52PM

This post has been deleted.

Whiplashy · 29-12-2017 07:52PM

Simona1986 wrote: »

And why do you go down through the gears if you have the clutch depressed the whole time?

I have absolutely no idea! It's just what I've always done. I essentially learned the basics off of google as when my father was "teaching" me to drive he pointed out the pedals and then said drive. When I went for lessons I didn't understand what the instructor was on about and he didn't elaborate.

CiniO · 29-12-2017 08:01PM

Whiplashy wrote: »

Is there a reason why I shouldn't coast

I remember years back when I was learning to drive, my instructor was always giving out about me coasting. I never really understood what he was on about though. Driving this evening a passenger pointed out that I coast every time I come up to a junction. It's how I've always driven, and I'm not too sure I'd actually be able to stop doing it. I press the clutch approaching the junction, keep it pressed while I'm going down through the gears and braking. I probably start clutching about 3 or 4 car lengths before I need to stop. Is there an actual reason why I shouldn't be doing it? The passenger today didn't know why, just that I shouldn't.

I can hardly think of any reasons why you should coast, maybe except of driving certain 2 stroke cars.

On the other hand, people seem the exaggerate coasting too much.
Indeed by doing so, you use more fuel, and you loose ability to accelerate quickly if needed, and wear down brakes more, and risk overheating them on steep descents, but there's hardly much more to this.
I don't get those comments about not being in control. You still can brake and turn, and on slippery surface you might even have better grip when coasting then when in gear.

Vronsky · 29-12-2017 08:02PM

dudara wrote: »

It essentially means that you have less control over the car as you’ve disengaged the engine by depressing the clutch.

It's just one of those things imo that's just a given as best practice without there being any solid justification for it. The only extra control it could possibly offer is to be able to quickly accelerate out of trouble but as long as the car is in gear when coasting it doesn't offer anything. And who accelerates out of trouble approaching a junction?

Avatar MIA · 29-12-2017 08:07PM

Vronsky wrote: »

It's just one of those things imo that's just a given as best practice without there being any solid justification for it. The only extra control it could possibly offer is to be able to quickly accelerate out of trouble but as long as the car is in gear when coasting it doesn't offer anything. And who accelerates out of trouble approaching a junction?

Also, as a fuel saving technique my car (an automatic Audi) when in efficiency mode it disengages entirely from the engine as a fuel saving measure... so (I think) the car can coast - when the accelerator is not pressed.

Rumple Stillson · 29-12-2017 08:15PM

Using the engine to break is good practice, especially in slippery conditions. It provides you with good traction as you come to a stop. I think once you do this properly once, it will be very clear and obvious why it is good practice.

Isambard · 29-12-2017 08:26PM

I call shenanigans, you couldn't pass your test doing this, as you've been doing it from years back ,I'm assuming you have done your test

JohnBoy26 · 29-12-2017 08:29PM

Isambard wrote: »

I call shenanigans, you couldn't pass your test doing this, as you've been doing it from years back ,I'm assuming you have done your test

Op never said they done it during a driving test though

rtron · 29-12-2017 08:31PM

When you go "down through the gears" I believe you can go for example from 5th to 3rd depending on the speed you drop to.

Vronsky · 29-12-2017 08:41PM

Rumple Stillson wrote: »

Using the engine to break is good practice, especially in slippery conditions. It provides you with good traction as you come to a stop. I think once you do this properly once, it will be very clear and obvious why it is good practice.

That doesn't make any sense. ABS which releases the wheels from locking up provides far more effective braking than slowing using engine braking.

I've used engine braking and clutch and braking approaching a junction and the former offers nothing over the latter in a modern car.

Maybe in the days before ABS it was useful, but like double clutching, it's not necessary now.

km991148 · 29-12-2017 08:41PM

rtron wrote: »

When you go "down through the gears" I believe you can go for example from 5th to 3rd depending on the speed you drop to.

You can go from any gear to any gear really, its about matching the gear to the speed - but its entirely pointless to select any gear at all when the clutch remains down!*

*Other than contriving the example of an emergency situation when having roughly the correct gear selected, even when coasting may help you gety out of trouble when you release the clutch.

km991148 · 29-12-2017 08:43PM

Vronsky wrote: »

That doesn't make any sense. ABS which releases the wheels from locking up provides far more effective braking than slowing using engine braking.

I've used engine braking and clutch and braking approaching a junction and the former offers nothing over the latter in a modern car.

Maybe in the days before ABS it was useful, but like double clutching, it's not necessary now.

As far as I know (based on UK where I passed) - engine breaking was taught for me (20 years ago) as not all cars were of the same standard. These days, engine breaking isn't taught at all apparently. Regardless, coasting is still forbidden / not taught.

Rumple Stillson · 29-12-2017 08:47PM

Vronsky wrote: »

That doesn't make any sense. ABS which releases the wheels from locking up provides far more effective braking than slowing using engine braking.

I've used engine braking and clutch and braking approaching a junction and the former offers nothing over the latter in a modern car.

Maybe in the days before ABS it was useful, but like double clutching, it's not necessary now.

Engine braking should be used in combination with normal braking for overall better traction, in manual cars.

As soon as the accelerator is released enough to slow the engine, engine braking comes into effect as long as the wheels remain connected via the transmission to the engine. A slipping or disengaged clutch, or a torque converter, would disengage the wheels or absorb braking energy. The braking force varies depending on the engine, and the gear the transmission is in. The lower the gear, the higher the braking effect due to higher rpm and the torque transferred through the transmission (higher torque is delivered from the engine in lower gears).
Engine braking avoids wear on brakes, and can help a driver maintain control of the vehicle. Active use of engine braking by shifting into a lower gear can help control speed while driving down very steep and long slopes, saving the brakes from overheating or excessive wear. If it is applied before the brakes have been used, it can leave the brakes available to make emergency stops. The desired speed is maintained by using engine braking to counteract gravitational acceleration. Potential transmission wear caused by engine braking can be mitigated by certain techniques. Slipping the clutch to complete a downshift wears the clutch plate as it slows the vehicle, doing the job of the brake pads or shoes. A well-executed rev-match in the same setting minimizes stresses on transmission components, so engine braking does the work of slowing the vehicle.

The_Captain · 29-12-2017 08:47PM

I just stick it in neutral and use the foot brake to stop

CiniO · 29-12-2017 09:18PM

Rumple Stillson wrote: »

Engine braking should be used in combination with normal braking for overall better traction, in manual cars.

I can't see anything about "better traction" in text you quoted.

In general, on slippery surfaces like ice, I would avoid engine braking, and rely on car brakes only whether car is equipped with ABS or not.

Whiplashy · 29-12-2017 09:22PM

Isambard wrote: »

I call shenanigans, you couldn't pass your test doing this, as you've been doing it from years back ,I'm assuming you have done your test

I have passed my test. I don't know if I coasted or not during it as I wasn't entirely sure what coasting was at the time. Passed about 8 years ago. I didn't realise until today that I was doing anything wrong, but I do remember my instructor complaining about me coasting and I don't remember ever approaching a junction any different.

Whiplashy · 29-12-2017 09:28PM

Oh actually, I think I my instructor might have said something about stopping in the gear I was in for the test, and then moving into first when stopped.

evolving_doors · 29-12-2017 09:29PM

The_Captain wrote: »

I just stick it in neutral and use the foot brake to stop

Like if you were slowing down from 80 to 0 say coming up to a toll bridge yould be in neutral breaking all the way!

Rumple Stillson · 29-12-2017 09:29PM

CiniO wrote: »

I can't see anything about "better traction" in text you quoted.

In general, on slippery surfaces like ice, I would avoid engine braking, and rely on car brakes only whether car is equipped with ABS or not.

It mentions having better control of the vehicle which is similar to having good traction throughout the braking process.

I'm struggling to clearly explain why using your engine to brake or going down through the gears is better than relying on your brakes alone. If you are coming down a steep hill, putting the car into a lower gear gives you greater control over the speed and stability of the car, I think that is obvious to everyone, you would never put the car out of gear and use the brakes in this situation.

It's not a huge leap to see that using lower and lower gears incrementally to come to a stop will provide you with greater control than simply braking.

I've driven many different vehicles of varying sizes and this is a technique I always apply, especially when they are loaded. While it may not be essential in a normal car, it remains good practice. Especially when it is icey or wet. In icey conditions for example, I try to minimise using the brakes as much as possible. Loss of control comes when the wheels begin to skid.

If you look at how racing drivers brake as they come to a corner, they employ the same technique. Down through the gears to improve braking and control.

Isambard · 29-12-2017 09:31PM

Whiplashy wrote: »

I have passed my test. I don't know if I coasted or not during it as I wasn't entirely sure what coasting was at the time. Passed about 8 years ago. I didn't realise until today that I was doing anything wrong, but I do remember my instructor complaining about me coasting and I don't remember ever approaching a junction any different.

In that case, it's likely you aren't doing anything wrong. Your passenger may not know what they are talking about and worrying you unnecessarily

In my view the correct procedure is to go down the gears to second and when you are ready to stop depress brake and clutch together

I don't believe you'd be doing the car any good slowing to a stop in 5th or 6th, and you wouldn't be ready to abort the stopping procedure if , for instance, the lights went green.

frozenfrozen · 29-12-2017 09:59PM

wasting your time changing down gears while holding the clutch just block change

mickdw · 29-12-2017 11:22PM

You need to be in gear and the right gear for ultimate control however for your average city driver not pushing the car to anywhere near its limits of grip or performance, they will get by fine.
One thing worth noting, being in gear as you slow for corners etc means the wheels are forcing the engine to stay turning. If for example a car developed a defect that resulted in poor idling or cut out on idle, you could lose steering assistance instantly and have a major accident. Using gears properly will keep everything spinning and wont allow engine to just drop off instantly.

Del2005 · 29-12-2017 11:59PM

CiniO wrote: »

I can't see anything about "better traction" in text you quoted.

In general, on slippery surfaces like ice, I would avoid engine braking, and rely on car brakes only whether car is equipped with ABS or not.

On slippy surfaces you should avoid using your brakes entirely. ABS doesn't work on slippy surfaces so going slow and engine braking is the safest way to drive.

Coasting was an issue when cars had drum brakes with wire cables. Modern cars with servo assisted hydraulic brakes don't need engine braking. The only downside is that you are needlessly burning a tiny amount of fuel. Still when driving manual I use the engine braking, the only thing I miss with auto, but I block change up and down.

CiniO · 30-12-2017 12:15AM

Del2005 wrote: »

On slippy surfaces you should avoid using your brakes entirely. ABS doesn't work on slippy surfaces so going slow and engine braking is the safest way to drive.

Sorry Del2005, but I have to totally disagree with you on that.

ABS does work on slippery surfaces, and while on loose snow or ice it doesn't help to reduce braking distance, but it allows car to be steerable with foot on brake pedal, which might be a huge advantage for most drivers.

It's fairly easy to loose control simply by taking your foot off the gas, simply due to fact that engine will start slowing down and slowing down your wheels, while car might still be going faster. That will mean skid, and lack of steering in case of FWD or most like side skid in case of RWD.

In loose snow, most effective way of braking is with locked wheels, so for driving in loose snow ideally you'd want to disable your ABS.
On compacted snow, ABS works very well, and probably even shortens braking distance comparing to no ABS.
And on ice, abs doesn't help much, but as before stated helps with steering.

When slowing down on slippery surface best to be in gear but with clutch pressed (gear in case you need to accelerate quickly), and use only brakes to slow down. Ideally feel the moment right before ABS kicks in and don't press any harder.

If you're on gear and do engine braking, this will only fiddle with your brakes, possibly causing driving axle to behave differently than other axle.

Maybe I didn't explain it very clear, but trust me - I have tens of thousands of kilometers driving experience in wintery conditions on slippery roads, and definitely know what is the best way to slow down and stay in control in such condition.

Rumple Stillson · 30-12-2017 07:46AM

CiniO wrote: »

Sorry Del2005, but I have to totally disagree with you on that.

ABS does work on slippery surfaces, and while on loose snow or ice it doesn't help to reduce braking distance, but it allows car to be steerable with foot on brake pedal, which might be a huge advantage for most drivers.

It's fairly easy to loose control simply by taking your foot off the gas, simply due to fact that engine will start slowing down and slowing down your wheels, while car might still be going faster. That will mean skid, and lack of steering in case of FWD or most like side skid in case of RWD.

In loose snow, most effective way of braking is with locked wheels, so for driving in loose snow ideally you'd want to disable your ABS.
On compacted snow, ABS works very well, and probably even shortens braking distance comparing to no ABS.
And on ice, abs doesn't help much, but as before stated helps with steering.

When slowing down on slippery surface best to be in gear but with clutch pressed (gear in case you need to accelerate quickly), and use only brakes to slow down. Ideally feel the moment right before ABS kicks in and don't press any harder.

If you're on gear and do engine braking, this will only fiddle with your brakes, possibly causing driving axle to behave differently than other axle.

Maybe I didn't explain it very clear, but trust me - I have tens of thousands of kilometers driving experience in wintery conditions on slippery roads, and definitely know what is the best way to slow down and stay in control in such condition.

It obviously works well for you but it is completely contrary to everything I do.

Its not one or the other by the way, I use both engine braking and the disc brakes to slow down. I always try to be in the correct gear for the speed I'm travelling.

Whatever about coming down through the gears, I know you will fail your driving test if you are braking with the transmission disengaged.

Kenny Logins · 30-12-2017 08:48AM

When you're coasting you only have momentum and brakes to control your speed, you can't use the engine/gears.
Seems completely alien to me, I just wouldn't be able to do it. Would feel like driving without a seatbelt.

Del2005 · 30-12-2017 09:30AM

CiniO wrote: »

Sorry Del2005, but I have to totally disagree with you on that.

ABS does work on slippery surfaces, and while on loose snow or ice it doesn't help to reduce braking distance, but it allows car to be steerable with foot on brake pedal, which might be a huge advantage for most drivers.

It's fairly easy to loose control simply by taking your foot off the gas, simply due to fact that engine will start slowing down and slowing down your wheels, while car might still be going faster. That will mean skid, and lack of steering in case of FWD or most like side skid in case of RWD.

In loose snow, most effective way of braking is with locked wheels, so for driving in loose snow ideally you'd want to disable your ABS.
On compacted snow, ABS works very well, and probably even shortens braking distance comparing to no ABS.
And on ice, abs doesn't help much, but as before stated helps with steering.

When slowing down on slippery surface best to be in gear but with clutch pressed (gear in case you need to accelerate quickly), and use only brakes to slow down. Ideally feel the moment right before ABS kicks in and don't press any harder.

If you're on gear and do engine braking, this will only fiddle with your brakes, possibly causing driving axle to behave differently than other axle.

Maybe I didn't explain it very clear, but trust me - I have tens of thousands of kilometers driving experience in wintery conditions on slippery roads, and definitely know what is the best way to slow down and stay in control in such condition.

That's fine for an experienced winter driver. In Ireland we aren't so engine braking and slowly is the safest option.

On Wednesday morning I was going to work and after clearing the frost off my car I always do a low speed brake test. Hit the brakes and the car slid. So for the remainder of the journey to work, all back roads some untreated, i took it handy and let off the throttle well before any corners or junction, no further slides.

ted1 · 30-12-2017 11:15AM

Rumple Stillson wrote: »

Using the engine to break is good practice, especially in slippery conditions. It provides you with good traction as you come to a stop. I think once you do this properly once, it will be very clear and obvious why it is good practice.

Advanced driving courses teach people to use the breaks instead if gears.

Brake pads are cheaper than gear boxes

ted1 · 30-12-2017 11:18AM

If you get hit while coasting you’ll be debt flying. Less chance if hitting other cars if you are in gear.

Rumple Stillson · 30-12-2017 11:26AM

ted1 wrote: »

Advanced driving courses teach people to use the breaks instead if gears.

Brake pads are cheaper than gear boxes

Do they suggest putting the car into neutral and coasting while braking?

ted1 · 30-12-2017 11:31AM

Rumple Stillson wrote: »

ted1 wrote: »

Advanced driving courses teach people to use the breaks instead if gears.

Brake pads are cheaper than gear boxes

Do they suggest putting the car into neutral and coasting while braking?

No

Del2005 · 30-12-2017 11:38AM

ted1 wrote: »

Advanced driving courses teach people to use the breaks instead if gears.

Brake pads are cheaper than gear boxes

In all my years of driving I've never damaged a gearbox. The driver who will damage a gearbox is not going to be a good driver if they only use their brakes.

travist · 30-12-2017 11:40AM

Toyotafanboi wrote: »

Staying in gear while slowing down in a modern car will save you fuel over coasting in neutral while braking too.

How’s that?

shaunr68 · 30-12-2017 11:45AM

travist wrote: »

How’s that?

Beat me to it. The idea of an engine ticking over using more fuel than an engine in gear and revving higher is counterintuitive.

Rumple Stillson · 30-12-2017 11:49AM

shaunr68 wrote: »

Beat me to it. The idea of an engine ticking over using more fuel than an engine in gear and revving higher is counterintuitive.

No fuel is burned during engine braking. Its created by a manifold vacuum

mickdw · 30-12-2017 12:15PM

shaunr68 wrote: »

Beat me to it. The idea of an engine ticking over using more fuel than an engine in gear and revving higher is counterintuitive.

While coasting, the engine must run under its own steam so uses a small amount of fuel even though only ticking over.
Slowing in gear such that the speed of the car causes the engine revs to increase means it is the car momentum that is driving the engine and therefore using no fuel.
A useful check to prove this is to coast to a stop and gear down to a stop. You will coast for a further distance than when in gear but you will use a small amount when coasting. You will use nothing when down changing to a stop but will come to a stop sooner. No free energy however when you want to slow down anyway, its best to avail of cars momentum to drive the engine and so use no fuel.

shaunr68 · 30-12-2017 12:41PM

Thanks fellas. Been driving over 30 years and driven all over the continent and never knew that. Cheers

se conman · 30-12-2017 12:55PM

This is a generalisation based on most people's "instinct"
Scenario 1;
You are approaching a junction at 80 kph in 5th gear. You depress the clutch and start breaking.
For some reason, the brakes fail or fail to adequately reduce the speed of the vehicle.
"Instinct" says push the brake pedal harder but doesn't tell you to take your foot off the clutch, in fact you will probably press the clutch just as hard as the brake.
Result, failure to stop.

Scenario 2;
Same junction, same speed.
You leave the vehicle in 5th gear and press the brake peddle.
Vehicle starts to slow down but then the brakes fail.
"Instinct" says press the brake harder but doesn't tell you to start pressing the clutch.
Engine brake has an effect and the vehicle stalls thus giving an "improved" chance of avoiding an accident.

There is also the "legacy" issue of older vehicles having a clutch cable rather than hydraulic clutch, the cable was more prone to failure.

CiniO · 30-12-2017 02:23PM

shaunr68 wrote: »

Thanks fellas. Been driving over 30 years and driven all over the continent and never knew that. Cheers

Because very likely 30 years ago this wasn't the case in your car.
In times of carburators, there was still fuel supplied to the engine, even when engine braking.

Only electronic fuel incjection introduced the feature to completely cut fuel supply from injector/injectors during engine braking, as it was very easy to implement.

CiniO · 30-12-2017 02:30PM

ted1 wrote: »

Advanced driving courses teach people to use the breaks instead if gears.

Brake pads are cheaper than gear boxes

I agree with that.
Can't see a reason to jump through all gears down during every slow down.

Normally I only go through one or two gears.

F.e driving 5 gear petrol car, slowing down from 80km/h to 0, I would reduce from 5th to 3rd to start slowing down and help with brake. When revs reach around 1000rpm, I would depress clutch, put gear to neutral and finish stopping with brake only.

Or when driving 6 gear diesel, doing 140km/h on motorway and slowing down to stop on toll gates, I would start slowing down just by taking foot off accelerator on 6th gear till maybe 110km/h, then reduce to 4th, and keep slowing down, and maybe again reduce to 2nd when speed reach around 30km/h.

Everytime putting gear on, I would press accelerator to match the revs so gear goes in smooth (to save gearbox).

If you match revs exactly, you don't even need to press clutch, but I wouldn't do it too often, as it might be hard on synchronisers if you don't match revs exactly.

CiniO · 30-12-2017 02:35PM

Del2005 wrote: »

That's fine for an experienced winter driver. In Ireland we aren't so engine braking and slowly is the safest option.

On Wednesday morning I was going to work and after clearing the frost off my car I always do a low speed brake test. Hit the brakes and the car slid. So for the remainder of the journey to work, all back roads some untreated, i took it handy and let off the throttle well before any corners or junction, no further slides.

The lower the revs, the lesser effect of engine braking.
So if you're on 3rd gear at 1800rpm and take your foot off the accelerator, even on quite slippery ice, you'll be grant you possibly won't loose a traction.

On the other hand if at the same speed, you engaged 1st gear and let the revs jump to 4000rpm, this could very likely mean skid.

Still think it's easiest to control a car in slippery conditions with brake only, depressing clutch everytime you brake. Especially on ice.
Snow itself is not really that slippery.

mickdw · 30-12-2017 02:36PM

CiniO wrote: »

Only electronic fuel incjection introduced the feature to completely cut fuel supply from injector/injectors during engine braking, as it was very easy to implement.

Absolutely and some believe that its only a theoretical argument that the car can drive the engine and so requires no fuel when slowing but as you say, the injectors actually cut off giving zero fuel input so its very much a fact.

BarryD2 · 30-12-2017 02:45PM

When I read OP title, thought at first they were referring to switching off the engine going downhill and freewheeling, as on a push bike. I used to do this in older cars we had, particularly coming down from Wicklow Gap towards Laragh in Wicklow. With judicious use of the brake, you could travel right down (3 miles maybe) using no fuel, until you met the road to Glendalough. But these older cars were designed without power steering and handled normally in terms of steering when switched off. Whereas now, power steering changes this substantially and lack of engine makes steering very heavy.

CiniO · 30-12-2017 02:48PM

BarryD2 wrote: »

When I read OP title, thought at first they were referring to switching off the engine going downhill and freewheeling, as on a push bike. I used to do this in older cars we had, particularly coming down from Wicklow Gap towards Laragh in Wicklow. With judicious use of the brake, you could travel right down (3 miles maybe) using no fuel, until you met the road to Glendalough. But these older cars were designed without power steering and handled normally in terms of steering when switched off. Whereas now, power steering changes this substantially and lack of engine makes steering very heavy.

It makes steering very heavy, as well brake pedal very heavy without vaccum for the servo, but still drivable if driver is aware of those limitations.

Is there a reason why I shouldn't coast

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