Friday 15th September 2006

IAM issues hot braking tip

Go easy on those brakes, says motoring body

---

Careful with those brakes, Eugene

The Institute of Advanced Motorists reckons we should lay off the brakes. Gentle, planned braking is something that all drivers should aspire to, says the IAM.

And if you don't think so, imagine being a passenger with somebody at the wheel  who is doing nothing except "emergency stops".  That kind of white knuckle ride may be extreme - but we all see examples daily of people who habitually leave it too late to brake for some reason (why else would there be all those skid marks on the tarmac?).

The key to good braking is anticipation.  Don't rely on the brakes to get you out of trouble because you failed to plan for the hazard ahead in good time.

A good way to develop sensitive braking is to imagine that you want to bring the car to a stop without your passengers noticing. 

By increasing pressure on the pedal smoothly you will "brush off" most of the speed -so at the right moment you will be able to bring your foot off the brake pedal without leaving the brakes biting to the bitter end.

This is possible with a bit of practice: ease up on the brake pedal imperceptibly just as you are about to stop - the last metre or so.

This allows you to roll gently to a stand-still without the vehicle's nose dipping or a jerk.

Braking should be a single, sustained use of the pedal - with the maximum pressure applied during the middle phase.

This gentle approach gives a good indication to the person following you that you are slowing down.  That in turn gives them more time to react and so reduces the chances of an inattentive driver "rear ending" your car. 

As an indicator brake lights are a bit crude: when you think about it, all the other indicators are telling other road users what you intend to do but the brake lights just confirm that you are already doing it!

[targarama]

All well and good, and I try to do this being an IAMer. However, you usually get someone nipping into the 'slow down' gap you've left and then have to adjust your planned braking and drop back.

[splodge s4]

'why else would there be all those skid marks on the tarmac'

Alot of long skid marks you see are nothing to do with late braking at all. They are from HGV twin back axle trailers with no load on them, the air brakes are sharp & when applied one of the axles with the least amount of weight locks up, bugger all the driver can do about it but if your behind it really stinks of burning rubber & leaves 2 black stripes often about 50+ metres long!

Edited by splodge s4 on Friday 15th September 11:13

[TUS 373]

targarama said:

All well and good, and I try to do this being an IAMer. However, you usually get someone nipping into the 'slow down' gap you've left and then have to adjust your planned braking and drop back.

Absolutely agree. In an ideal world, everone would take a smooth and planned drive. It just takes one or two people to jump into a space on a motorway, cut down on your available braking distance, and then you are on the brakes again. The only way to avoid this, is I believe, to stay at home.

What I have found is that recently becoming a country dwelling 4x4 driver (not a townie), is that the higher driving position opens up a better view for me to see hazards and plan a smoother drive. At the same time, this also helps make better use of the gas pedal as well as the brake so helping me drive smoother, more comfortably for passengers and as economically as I can.

[martaay]

More great knowledge from the IAM, its as if we wouldn't have had any idea to brake smoothly until reading that article...

An idea for the next article - "did you know that by not accelerating hard your car will be more economical"

[unobtainum]

If you need this advice your driving is below standard anyway, so unlikely that you will heed it.

Too many excuses too.

[oppressed mass]

just as importantly and surprisingly absent is correct use of the gears to utilise engine braking. do this right and often avoid the middle pedal altogether (alright so i drive a diesel manual). It is harder in modern petrols (as the flywheel retains significantly more energy - driving experience sacrificed for emissions) but even so it still has an effect..

[Timberwolf]

martaay said:

An idea for the next article - "did you know that by not accelerating hard your car will be more economical"

It will also be boring, slow, and won't make any nice noises...

[fatboy b]

What a load of old bollox! Gentle use of the brakes has one outcome - glazed discs. When I get behind the wheel of my girlfriend's Seat after she's been in it for a bit, the brakes are almost frightening. In fact I told her to mention it to the mechanic at the last service. His advice? You gotta start using your brakes a bit more.

[cptsideways]

Unfortunatley it won't help one the bit habitual lemmings on the motorway who "CONSTANTLY" accelerate & brake all day long as they are following too close.

I do have a little solution, follow at a big big distance, flash ones headlights everytime they brake, they soon start looking, then just anticpate their moves & flash a second or so before they bang them on again. Seems to work a treat & about one in three see to get that they are being complete plonkers & idiots

What really stuns me is that people this stupid are actually employed by somebody how the hell did they all get through being that STUPID, they can't all work for the government surely?


Rant over (as you may well gather its a pet hate of mine)

[dnb]

Timberwolf said:

martaay said:

An idea for the next article - "did you know that by not accelerating hard your car will be more economical"

It will also be boring, slow, and won't make any nice noises...

And could also be argued to be inaccurate too.

Engines are more efficient at peak torque. Therefore surely you're better off using this to accelerate briskly (for a short time), then cruising at your chosen speed rather than gently accelerating (for a long time) to the same cruising speed. Off to do some maths to back this up...

[dragonship]

well said 'oppressed mass' the problem is that the current crop of newish drivers are never taught to do the engine brake stuff, i taught my son and he said the instructors don't like you to do it. I note that he does it now as we both drive fairly quick cars.

[sublimatica]

The IAM may be preaching to the choir here, but the Pistonheads readership isn't representative of the numpties on the roads. There are plenty of people (me included) who've never been taught these kind of driving-improvement techniques. I've learnt them over time because I read these kind of forums. The people that don't will never have had this advice.

I don't think it's stating the bleedin' obvious to the public, so long as the public's prepared to listen. Most people don't give a crap though so why would they be bothered to listen? It's a shame. These kind of techniques should be included in the driving test.

[sublimatica]

dnb said:

Timberwolf said:

martaay said:

An idea for the next article - "did you know that by not accelerating hard your car will be more economical"

It will also be boring, slow, and won't make any nice noises...

And could also be argued to be inaccurate too.

Engines are more efficient at peak torque. Therefore surely you're better off using this to accelerate briskly (for a short time), then cruising at your chosen speed rather than gently accelerating (for a long time) to the same cruising speed. Off to do some maths to back this up...

The fuel economy read out in my wife's Saab would disagree with your proposal...

When she drives it: 34mpg
When I drive it: 30mpg

[renny]

sublimatica said:

dnb said:

Timberwolf said:

martaay said:

An idea for the next article - "did you know that by not accelerating hard your car will be more economical"

It will also be boring, slow, and won't make any nice noises...

And could also be argued to be inaccurate too.

Engines are more efficient at peak torque. Therefore surely you're better off using this to accelerate briskly (for a short time), then cruising at your chosen speed rather than gently accelerating (for a long time) to the same cruising speed. Off to do some maths to back this up...

The fuel economy read out in my wife's Saab would disagree with your proposal...

When she drives it: 34mpg
When I drive it: 30mpg

Ah, but is the cruising speed the same? I bet not

[dnb]

You have to compare like with like. You could be accelerating to a higher cruising speed, braking heavily for the corners and accelerating hard again, whereas your wife is a smooth progressive driver who generally maintains a higher average speed... You could be driving different routes, different traffic conditions etc. Far too many variables to be considered so you can't prove or disprove anything I've said...

My wife gets better economy than me too.

Still working on the maths. It's more difficult than I thought to model this.

Edited by dnb on Friday 15th September 13:15

[GreenV8S]

targarama said:

All well and good, and I try to do this being an IAMer. However, you usually get someone nipping into the 'slow down' gap you've left and then have to adjust your planned braking and drop back.

This is often quoted as being a problem, but I hardly use the brakes at all and keep what I consider a reasonably safe gap, and people don't cut in front of me often enough to be a problem.

[dnb]

Hmmm. The question is simple: "Is it better to inefficiently generate Z bhp for 2X seconds or efficiently generate Y for X seconds", where Y >> Z.

The answer is unfortunately quite hard - more than excel and half a lunchtime can cope with.

The maths says that it makes so little difference it's not worth worrying about provided the "journey" is significantly longer than the acceleration period - so this doesn't work at Santa Pod for example! I have made a few dodgy assumptions so these could be breaking down (the main one being that I can approximate efficiency from certain engine parameters and the energy in a litre of fuel). This is a whole new topic, so I'll stop dragging this one O/T now.

Oh well, back to designing radars now.

[racelogic]

Burn and coast is the most economical way of driving a petrol car. This is because when the throttle is not fully open, the engine works under a vacuum, which is less efficient. That is why diesels are more efficient than petrol engines cars because the throttle is wide open at all times, and the power is regulated by the flow of fuel.

If you accelerate on 80% throttle up to a speed, knock it into neutral, then coast down to a slow speed, and repeat, you will get a massive improvement in economy, but you will also piss off the people behind, and your passengers.

[splodge s4]

dnb said:

My wife gets better economy than me too.

Edited by dnb on Friday 15th September 13:15

Could also be because shes lighter than you & nothing to do with driving styles! (no offence intended mate)!

[targarama]

GreenV8S said:

targarama said:

All well and good, and I try to do this being an IAMer. However, you usually get someone nipping into the 'slow down' gap you've left and then have to adjust your planned braking and drop back.

This is often quoted as being a problem, but I hardly use the brakes at all and keep what I consider a reasonably safe gap, and people don't cut in front of me often enough to be a problem.

Ah, but if you're talking about when driving the TVR - it has massive engine braking compared to normal cars. I hardly need to brake in my TVR and often have to touch the brake pedal to warn cars behind that I'm slowing - most obvious on the motorway.