I was asked a very similar question some time ago - but, thankfully, the question was a bit simpler.
If you are going along at a given speed, and want to stop, is it best to slam on, and stop quickly, or to brake very gently to a stop?
I didn't have any definitive answer, but here's my reasoning.
The total energy in the vehicle is the same however you brake, so, approximately the same amount of heat must be generated. The gentle braking has a small advantage by dissipating more of this energy to wind and rolling resistance.
The brakes convert the kinetic energy to heat. During a slow brake application, the heat transfer mechanisms can keep the pad/disc interface at a lower temperature. As brakes wear more at high temperatures, gentle braking is a good thing.
During a rapid braking application, owing to the thermal capacity of the material imediately around the pad/disc interface, heat cannot get away, and the resulting interface temperature will be higher.
Also, during light braking, there isn't much weight transfer, which, depending on the type of brake pressure reduction to the rear axle means that braking may be more equally distributed between all four wheels, again, reducing the temperature at the pad/disc interface.
Number_Cruncher
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Would agree with all the comments regarding clutch, gearbox, accelerator used as smoothly as possible, and brakes under normal driving conditions.
But in the handbook for my Saab, it says under Braking: "When driving fast, you can help prolong the life of the brakes by braking harder for short periods, rather than braking more moderately for longer periods."
Also says for long descents, use engine braking as much as possible, do not constantly use brakes or they could overheat.
Rich.
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Mechanically sympathetic as I believe I am, I wince when I see and hear people starting cold engines and immediately racing away or slipping the clutch to hold the car on a hill junction or high-revving the engine rather than changing up a gear in good time.... I could go on but don't want to bore you all further.
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I always try to avoid any kind of lurching when changing gears, believing that the smoother the change the more mechanical sympathy. This method *may* reduce clutch life though as by definition you're slipping the clutch slightly to compensate for any inaccuracy in the rev-matching as you lift the clutch up.
Changing up gears higher than 1-2 I try to match the revs as close as I can and bring up the clutch quickly to avoid unnecessary slippage. 1-2 is a special case as the car will lurch easily if you're only slightly out so I lift the clutch gently in this case.
I also never start in second, and apply as few revs as the car will allow without complaint when setting off/reversing.
Block-changing as late (and therefore as slowly) as possible when reaching junctions, roundabouts etc and using engine braking approaching roundabouts is something I try to implement wherever possible as well.
And, worse comes to worst, and the above does wear the clutch, pick a car where the clutch change is a simple job (ie not engine-out). That way you can live safe in the knowledge that you're not hurting the engine and transmission and, if the clutch does need replacing, at least it'll be as cheap as a set of tyres or brakes so won't hurt too much.
All this sound sensible?
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Unless you are quite thick, the way to develop mechanical sympathy is to drive cars that are well past their best. While pulling brakes and excessive steering backlash are not for the beginner, much progress can be made on cars with juddery clutches and in particular with demolished synchromesh on one or more gears, necessitating carefully timed gear lever movements or even double-declutching on up changes as well as down. Stands you in good stead, poverty.
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And if you drove a vintage Lagonda with the sliding pinion Z box you had to be sympathetic or you would not get into the next gear.
(I think, by the way, that syncromesh, to say nothing of automatic, ruined motoring. They make it too easy for Tom, Dick and Harry to get on the road!)
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(I think, by the way, that syncromesh, to say nothing of automatic, ruined motoring.
Look at the States!
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And if you drove a vintage Lagonda with the sliding pinion Z box you had to be sympathetic or you would not get into the next gear. (I think, by the way, that syncromesh, to say nothing of automatic, ruined motoring. They make it too easy for Tom, Dick and Harry to get on the road!)
Hear hear, but not a popular view I fear.
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Make 'em all double-declutch, I say...
Somehow I doubt that a gentle feeding-in of the clutch causes more wear than a sudden jolt as the mismatched speeds are resolved. It's the same amount of energy, after all.
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Believe it or not, I do actually double declutch but only when approaching a hazard at a fair speed to drop it into third or even second smoothly.
Dad etched it into me when I was learning.
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A few years ago the clutch cable on my company Mondeo snapped when I was about 7 miles from home and anxious to get there so I drove the rest of the way without using the clutch. The following morning the breakdown man came to replace the cable and did not believe me, he thought it must have gone as I arrived. Yet driving clutchless is not all that difficult with practice and can be a useful skill.
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i used to see how far i could drive my old mk1 escort without using the clutch it is quite easy once you get the feeling for the engine noise and road speed,however i would not recommend it on your average modern motor.
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\"a little man in a big world/\"
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i used to see how far i could drive my old mk1 escort without using the clutch.
Quite a few years ago my brother started and drove my 1600E with no means of disengauging the clutch. This was from the A48 south of Gloucester via the old Severn Bridge to Hounslow near Heathrow certainly over 100 miles all be it a lot of M4.
This was in very light traffic early Sunday morning and was completed non stop.
It presented a few challenges like the Severn Bridge toll and some traffic lights.
The spigot bearing had failed, locking the gearbox to the engine.
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Yet driving clutchless isnot all that difficult with practice and can be a useful skill.
Wow, terrific. Learned it on a Cortina 1500 Estate hire car in the mid-60s... you can regret trying it in some cars though, believe me.
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Why do the majority of car drivers nowadays never use the handbrake between setting off and arriving at their destination?
I was recently behind a Shogun in dense traffic. We were hardly moving, and going up a long hill to a junction. She held it on the clutch constantly for what must have been 20 minutes... Can't help but notice the number who do it from the telltale back wheels of the car in front rolling back and forth on up-hill junctions.
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because a lot of people cant do hill starts with handbrake on thats unfortunately why. RichardM .
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\"a little man in a big world/\"
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Not many people drive sympathetically. If I'm selling a car I obviously get punters turning up and wanting a test drive. I often have to bite my tongue. Worst thing is these characters who shift gear abruptly and floor throttle between each change. Lots of people also brake very late. You often see low-mileage cars with shot-out brake discs because rep-style driver has hammered it.
I always try to drive as smoothly as possible. Go gentle till the engine and transmission have warmed up. Press gently on the gearstick and let the synchro work for you - the lever will 'fall' into gear. Hard shifting and hard clutch engagement wears out synchro and imposes shock loads on the transmission and drivetrain - don't do it any good at all.
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i have a reputation for kicking customers out of my cars if they dont drive properly my record is 2 miles from my base, i tell them if they want to drive back on the test drive after i have warmed the car up that they must drive within the law and no stupid emergancy stops or hands off the wheel rubbish if they disobey my standards then they get kicked out i want to live another day and dont suffer fools,i dont stand for car revvers either.
I must add im still in business and doing alright.
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\"a little man in a big world/\"
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Well said Oldman. I have sold mostly Mercs, so don't get young 'nutters' just characters who are used to flooring the throttle between every (manual) gearchange. I sold a manual 190E to a bloke who turned up in great big hiking boots (a very nice chap actually) - but he kept stalling the engine on account of the boots!
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Out walking today in the country and met an old school friend who retired recently from his work for most of his life as Transport manager for a well known household brand Company. He will talk cars and HGVs all day if you let him
The conversation got round to fuel consumption and maintenance.
He stated that HGVs do around 8mpg and if they could achieve a saving of one half mile per gallon this related to thousands of pounds savings in one year for the company.
They tried every new innovation and gadgets over the last thirty years and their meticulous records showed that none of them worked until the last one.
This was a computer of some sort installed in the vehicle which monitored and recorded the complete driving pattern of the user.
It records at what revs gear changes are made.
Braking patterns showing hard use which affected economy.
Engine at optimum running speed for each gear to maximise fuel consumption.
Any time spent at tick over above normal traffic use.
A driver training scheme for drivers and a bonus for achievement.
The results in both fuel saving and lower vehicle wear and maintenance were outstanding.
And when the vehicle returns to base and passes the Office window it downloadeds the information automatically giving an instant insight to the Transport manager of his drivers performance.
There was many more parameters of this system which standing in the freezing cold I can be excused for forgetting, but his message was that all the gadgets in the world do nothing for fuel saving or vehicle life and it all comes down to what the driver can achieve with education and training.
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I tend to change gear lightly using a pentle push with 2 fingers. I alwaysb avoid undue breaking by anticipating problems etc and taking my foot of the gas or reducing speed using a combiation of the above and changeing down.
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Most contributors to this thread understand something of supreme importance: the aesthetic component of the maximum progress/minimum stress project.
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"Most contributors to this thread understand something of supreme importance: the aesthetic component of the maximum progress/minimum stress project."
Indeed, but can you remember how you acquired this knowledge/skill? I put it down to years of mechanical practice, starting with Meccano, but hopefully there are other ways, although not always apparent in young men's driving (present company excepted, of course!).
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"Most contributors to this thread understand something of supreme importance: the aesthetic component of the maximum progress/minimum stress project." Indeed, but can you remember how you acquired this knowledge/skill? I put it down to years of mechanical practice, starting with Meccano, but hopefully there are other ways, although not always apparent in young men's driving (present company excepted, of course!).
Essentially it's inherent in some individuals. Mechanical understanding and mechanical sympathy are different; you can have one without the other. I too was always 'mechanically minded' with an interest in mechanisms; I too enjoyed Meccano from an early age. My father was similar and encouraged me, bless him. But I know people who have wide technical understanding and can't drive for toffee nuts. Either they just don't care, or they lack fine physical coordination or the ability to develop it, or the presence of other traffic makes them nervous, or some combination of these.
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I know people who have widetechnical understanding and can't drive for toffee nuts. Either they just don't care, or they lack fine physical coordination or the ability to develop it, or the presence of other traffic makes them nervous, or some combination of these.
On reflection: there are people with neither mechanical sympathy nor wide technical understanding who can become quite talented drivers, having the right sort of athlete's mindset and so on. Of course mechanical sympathy and a measure of understanding will make a talented driver even better; why Fangio was so good, he had a delicate touch. Still, these qualities are all separate. Driving as a practical art does not demand high cognitive activity, but a constant exercise of intellect. Car people (like us) have these things in varying proportions and the right kind of skewed mentality to blend them together in a seamless, elegant flow. If all foes well of course. I wouldn't claim to be exemplary myself.
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Has anyone else noticed some posts evidently from another website apparently talking about chocolate? Some glitch in the web perhaps?
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Thorntons I believe. May I have my complimentary box delivered?
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Nortones2....Amazing !. was standing outside his house talking to him for an hour yesterday.
Will get Paul to forward your box. How did you know, surely other Companies must do the same.
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Alvin: I'd been looking at some H&S issues, and came across Thorntons mentioned in a case study - actually 2 - about cutting driving accidents. Hence my lucky guess!
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lol, from my experience, the salemen quite often abuse the vehicles too. When I test drove a Corsa the first thing the salesman did was floor it, and go up to 50mph in a 40mph limit, which is IMHO totally inappropriate. It was a cold day, and the Corsa was brand new, ie. less than 5 miles on the clock IIRC.
On test drives I generally give the engines a little abuse before they've warmed up because I never know how short the test will be. The cars quite often barely have chance to warm up on a test drive. There was one car that I went gentle on, and that's because I didn't feel rushed because the salesman just swap keys, and let me go exactly where I want. I generally treated it really well, I hit about 5000rpm a couple of times, but that's not too bad. I wouldn't abuse a 2nd hand car though, only a new one, which would be sold as a demonstrator.
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lol, from my experience, the salemen quite often abuse the vehicles too.
I've found this as well.
When testing the Primera, the salesman didn't seem to know what clutch control was. Clunk, every time the cluth pedal was let up. Not the car's fault as I was managing totally smooth gearchanges from the third attempt onwards...
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On a similar note, I've been following HJ's advice about taking my oil burner up to 4500 rpm every so often to help clean the injectors etc.
Is this damaging to any other components? (It is after all only 500rpm from the redline) It's done as I'm nearly home, after about 10 miles down the A3 so it should be nice and warm. I idle for 30 ish seconds before switching off.
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I commute to work along a main A road. Every now and then I do the journey without using 5th gear to keep the revs up a bit to gently blow away the injector cobwebs. Still a problem with loss of power, suspect wastegate isn't sealing properly.
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I doubt it, I thrash mine regularly and our diesel tractor runs at a shade below the red line for hours at a time when driving the PTO.
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I doubt it, I thrash mine regularly and our diesel tractor runs at a shade below the red line for hours at a time when driving the PTO.
What's one of those?
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Power Take Off. An extra gearbox which allows you to run machinary such as hay turners / balers etc, or even a generator.
On our tractor with the 540RPM gear engaged the engine needs to be running about half an inch short of the red line on the tachometer.
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..... and I always rev-limit my driving style until the water temperature gauge hits its normal operating temperature.
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Exactly right. LJK Setright's rule of thumb was to use no more than half max revs until warmed up, the point being that you want to limit the stresses until everything has reached working temperature (and hence size). Labouring the engine at low revs probably isn't ideal, either!
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The oil will be nowhere near warm though. The water will heat up as that's what it does, carries heat away.
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I think that mechanical sympathy is something you're born with. It's not easily taught. It includes a degree of economy (not wanting to break things) together with respect for the machine. There's no need to red-line cold engines, slam through the gears, labour the engine or brake to a jolt to travel quickly. Driving smoothly is satisfying.
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Yep - my Dad was a lorry driver, and driving always intersted me. I just picked up good habits.
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"The water will heat up as that's what it does, carries heat away."
So does the oil, hence oil coolers in high performance engines.
I know how temperature affects viscosity, but does it affect lubricity much? Like you, I have the feeling that warm oil works better, but not exactly sure how...
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The anti wear additives only start to work properly as the oil warms up.
But the different metals in an engine expand at different rates, if you look at a block that's been driven badly you can see the scour marks on piston or cylinder walls.
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