using clutch to control car speed going down steep hill
Discussion
DonkeyApple said:
On a RWD car there is absolutely no difference between the two actions. Both are applying braking force only to the driven wheels and the same laws of physics apply to both.
Both apply a decelerative force, yes. The handbraking force should be an order higher than the engine braking force.When you get your car MOT'd, they test the force of your handbrake by rotating the rear wheels. If you were to try that test with simply an engaged transmission, you'd just alter the revs of the engine and the engine would stall.
The braking force applied by the handbrake should be an order higher than the braking force possible using engine braking.
DonkeyApple said:
I'm intrigued as to how such action can be argued to be risk free as appears to be mooted? Or, for that matter, why cars traditionally have a braking bias to the front wheels? Or why matching revs has any place?
Do you REALLY think engine braking can lock wheels on normal tarmac ? Maybe when trying to bumpstart a RWD diesel (high compression ratio engine)Cars have a front braking bias because physics (duh!), the centre of weight moves forwards when strong braking force is applied, so the rears become light, reducing their traction.
Have you ever felt yourself come out of your seat when using engine braking ? No, you haven't, the force isn't strong enough, UNLIKE what can be achieved with the brakes.
I think your risk-o-meter needs recalibration.
gavsdavs said:
DonkeyApple said:
On a RWD car there is absolutely no difference between the two actions. Both are applying braking force only to the driven wheels and the same laws of physics apply to both.
Both apply a decelerative force, yes. The handbraking force should be an order higher than the engine braking force.When you get your car MOT'd, they test the force of your handbrake by rotating the rear wheels. If you were to try that test with simply an engaged transmission, you'd just alter the revs of the engine and the engine would stall.
The braking force applied by the handbrake should be an order higher than the braking force possible using engine braking.
DonkeyApple said:
I'm intrigued as to how such action can be argued to be risk free as appears to be mooted? Or, for that matter, why cars traditionally have a braking bias to the front wheels? Or why matching revs has any place?
Do you REALLY think engine braking can lock wheels on normal tarmac ? Maybe when trying to bumpstart a RWD diesel (high compression ratio engine)Cars have a front braking bias because physics (duh!), the centre of weight moves forwards when strong braking force is applied, so the rears become light, reducing their traction.
Have you ever felt yourself come out of your seat when using engine braking ? No, you haven't, the force isn't strong enough, UNLIKE what can be achieved with the brakes.
I think your risk-o-meter needs recalibration.
And again, who on earth is mentioning lock up? Only you chaps. Do you now think that the only way to apply a handbrake is to pull it on to its maximum braking force?!!!!
The fact that you appear to believe that you can apply a braking force less than 'lock up' to the rear wheels of a car and not risk any ramifications at all is frankly extremely worrying and serves to highlight how many incidents occur and why it was worth me highlighting that engine braking at any level is not a risk free action.
As I said before, I wish you good luck. But do honestly recomend that instead of continuing to try and argue against the laws of physics you have a think about some of the things you have written.
DonkeyApple said:
I'm afraid not. The application of a handbrake is not binary. It can be applied at any level from zero to max.
And again, who on earth is mentioning lock up? Only you chaps. Do you now think that the only way to apply a handbrake is to pull it on to its maximum braking force?!!!!
No, i'm afraid it's you, who mentioned a TVR spinning due the engine braking lockup.And again, who on earth is mentioning lock up? Only you chaps. Do you now think that the only way to apply a handbrake is to pull it on to its maximum braking force?!!!!
Have you ever seen the handbrake test done during an MOT ? (simple question, yes or no is the only answer)
Do you think the same thing would happen if the engine braking was anywhere near what a hydraulic disc brake system can apply ?
DonkeyApple said:
The fact that you appear to believe that you can apply a braking force less than 'lock up' to the rear wheels of a car and not risk any ramifications at all is frankly extremely worrying and serves to highlight how many incidents occur and why it was worth me highlighting that engine braking at any level is not a risk free action.
As I said before, I wish you good luck. But do honestly recomend that instead of continuing to try and argue against the laws of physics you have a think about some of the things you have written.
I do worry about the things I have written. I've attempted to explained the difference in forces applied between the braking system (specifically intended to stop/slow a vehicle), and the use of a form of drag (engine braking). The difference in forces that can be applied by these systems is hugely different, yet you seems to think the effect of each is comparable (and hence the shrieking/wailing/seals and babies will die comments).As I said before, I wish you good luck. But do honestly recomend that instead of continuing to try and argue against the laws of physics you have a think about some of the things you have written.
gavsdavs said:
DonkeyApple said:
I'm afraid not. The application of a handbrake is not binary. It can be applied at any level from zero to max.
And again, who on earth is mentioning lock up? Only you chaps. Do you now think that the only way to apply a handbrake is to pull it on to its maximum braking force?!!!!
No, i'm afraid it's you, who mentioned a TVR spinning due the engine braking lockup.And again, who on earth is mentioning lock up? Only you chaps. Do you now think that the only way to apply a handbrake is to pull it on to its maximum braking force?!!!!
Have you ever seen the handbrake test done during an MOT ? (simple question, yes or no is the only answer)
Do you think the same thing would happen if the engine braking was anywhere near what a hydraulic disc brake system can apply ?
DonkeyApple said:
The fact that you appear to believe that you can apply a braking force less than 'lock up' to the rear wheels of a car and not risk any ramifications at all is frankly extremely worrying and serves to highlight how many incidents occur and why it was worth me highlighting that engine braking at any level is not a risk free action.
As I said before, I wish you good luck. But do honestly recomend that instead of continuing to try and argue against the laws of physics you have a think about some of the things you have written.
I do worry about the things I have written. I've attempted to explained the difference in forces applied between the braking system (specifically intended to stop/slow a vehicle), and the use of a form of drag (engine braking). The difference in forces that can be applied by these systems is hugely different, yet you seems to think the effect of each is comparable (and hence the shrieking/wailing/seals and babies will die comments).As I said before, I wish you good luck. But do honestly recomend that instead of continuing to try and argue against the laws of physics you have a think about some of the things you have written.
DonkeyApple said:
Yup. But always worth bearing in mind that with a rwd car you are applying braking only on the rear wheels, just like applying the handbrake. And when people abuse engine braking they can get a little bit of a surprise.
Interestingly, it seems quite a common issue when people who have spent years ragging fwd cars switch to a performance RWD car and then wonder what the juddering f
k has just happened as they drift backwards over a roundabout. 
I recall watching a chap in a TVR coming down Fish Hill in the Cotswolds in the wet. He was holding a lower gear all the way down and using engine braking to help control speed, as all of is would in manuals, except when he got into the right hand bend towards the bottom off he went up the grass backwards.
And again, because of that you are going on about MOts and hand brake braking ability on full load as if it is not possible to use a handbrake to do anything other than lock the wheels!!!Interestingly, it seems quite a common issue when people who have spent years ragging fwd cars switch to a performance RWD car and then wonder what the juddering f
k has just happened as they drift backwards over a roundabout. I recall watching a chap in a TVR coming down Fish Hill in the Cotswolds in the wet. He was holding a lower gear all the way down and using engine braking to help control speed, as all of is would in manuals, except when he got into the right hand bend towards the bottom off he went up the grass backwards.
Please stop talking about locking up wheels as it is not remotely relevant to anything here. Unless of course you are trying to imply that you can only unbalance a car with rear wheel braking by locking up the rear wheels!!!! But no one could think that.
What we are talking about here is something very simple. And that is that the application of a braking force purely to the driven wheels in a RWD car risks unsettling it. That matter really can't even be up for debate. You don't need to lock up wheels to risk breaking traction!!!!
Please think this through.
gavsdavs said:
B'stard Child said:
Yep it certainly can - hit 3rd instead of 5th flat out in 4th - it's fun.......
I had a mate blow up an exige doing that Engine amazingly survived.....
It was an extreme example but on circuit in my track car I can frequently feel the car steering from the rear under engine braking - sure they aren't locking but the retardation is enough to unsettle the car on approach to corners.
Out on the road with a RWD car - throw in a surface change - maybe a little bit of damp and a slightly too early downshift or a shift from 5th to 2nd instead of 4th and you could be in a spot of bother.
At the end of the day under engine braking alone on a RWD car you are in a situation where all the retardation is being supplied to the back wheels - that's what the "Donkey chap" is trying to point out
Edited by B'stard Child on Thursday 30th July 13:39
DonkeyApple said:
Please stop talking about locking up wheels as it is not remotely relevant to anything here. Unless of course you are trying to imply that you can only unbalance a car with rear wheel braking by locking up the rear wheels!!!! But no one could think that.
But it IS relevant, because it's exactly the scare story you first wheeled out of justify your argument. (tvr going down fish hill in the wet)DonkeyApple said:
What we are talking about here is something very simple. And that is that the application of a braking force purely to the driven wheels in a RWD car risks unsettling it. That matter really can't even be up for debate. You don't need to lock up wheels to risk breaking traction!!!!
Please think this through.
I have thought this though, and I have thought that you are the last person we should be considering listening to on this subject, because you appear not to understand what "order of magnitude difference" means.Please think this through.
gavsdavs said:
DonkeyApple said:
Please stop talking about locking up wheels as it is not remotely relevant to anything here. Unless of course you are trying to imply that you can only unbalance a car with rear wheel braking by locking up the rear wheels!!!! But no one could think that.
But it IS relevant, because it's exactly the scare story you first wheeled out of justify your argument. (tvr going down fish hill in the wet)DonkeyApple said:
What we are talking about here is something very simple. And that is that the application of a braking force purely to the driven wheels in a RWD car risks unsettling it. That matter really can't even be up for debate. You don't need to lock up wheels to risk breaking traction!!!!
Please think this through.
I have thought this though, and I have thought that you are the last person we should be considering listening to on this subject, because you appear not to understand what "order of magnitude difference" means.Please think this through.
And your MoT stuff isn't at all relevent precisely because we are not talking about locking wheels up.
If you think that you can only unsettle a car by locking a wheel then God help you. Seriously.
And if you think that applying a braking force to the rear wheels whether by use of the hand brake or use of the drivetrain uses different laws of physics then God help you.
Please stop trying to argue what was a really very simple and basic throw away remark by trying to invent things that were never said or scenarios that were never raised.
Just stop, it is actually embarrassing to see such a strong level of mis comprehension.
DonkeyApple said:
B'stard Child said:
Is this the 5min argument or are you going for the full 1 hour 
I thought I'd start with the 5 minute one before deciding on visiting N,P&E. I decided never to visit N,P&E again after one short visit
B'stard Child said:
DonkeyApple said:
B'stard Child said:
Is this the 5min argument or are you going for the full 1 hour
I thought I'd start with the 5 minute one before deciding on visiting N,P&E. I decided never to visit N,P&E again after one short visit
DonkeyApple said:
Please stop. You've been banging on about locking up. As I've shown, I never once mentioned anything of the sort, you made it all up.
And your MoT stuff isn't at all relevent precisely because we are not talking about locking wheels up.
If you think that you can only unsettle a car by locking a wheel then God help you. Seriously.
And if you think that applying a braking force to the rear wheels whether by use of the hand brake or use of the drivetrain uses different laws of physics then God help you.
Please stop trying to argue what was a really very simple and basic throw away remark by trying to invent things that were never said or scenarios that were never raised.
Just stop, it is actually embarrassing to see such a strong level of mis comprehension.
It's really worrying to see someone who works in derivatives to not understand what "orders of magnitude" means. Oh, wait, was that what happened on 2008 ? And your MoT stuff isn't at all relevent precisely because we are not talking about locking wheels up.
If you think that you can only unsettle a car by locking a wheel then God help you. Seriously.
And if you think that applying a braking force to the rear wheels whether by use of the hand brake or use of the drivetrain uses different laws of physics then God help you.
Please stop trying to argue what was a really very simple and basic throw away remark by trying to invent things that were never said or scenarios that were never raised.
Just stop, it is actually embarrassing to see such a strong level of mis comprehension.
Maybe you do, but you don't want to admit it because you can't speak for the foot in your mouth
gavsdavs said:
It's really worrying to see someone who works in derivatives to not understand what "orders of magnitude" means. Oh, wait, was that what happened on 2008 ?
Maybe you do, but you don't want to admit it because you can't speak for the foot in your mouth
So you now move on to trying to insult what I do for a living? Having failed at making up claims as to what I previously wrote!Maybe you do, but you don't want to admit it because you can't speak for the foot in your mouth
We get that you don't understand but instead of resorting to insults and childishness why not have an ounce of dignity and go and educate yourself on something that may transpire to be rather beneficial to you as you drive a RWD car!!!!!
Now, I've tried to help and I've given you some good advice. I hope you learn from it but please understand that I simply cannot help you any further and I have also lost any desire to try and help you understand once you chose to distort words and being offensive.
I wish you luck and I genuinely hope you learn about unbalanced braking from a book and not from a life experience. For all our sakes. Bye.
DonkeyApple said:
So you now move on to trying to insult what I do for a living? Having failed at making up claims as to what I previously wrote!
We get that you don't understand but instead of resorting to insults and childishness why not have an ounce of dignity and go and educate yourself on something that may transpire to be rather beneficial to you as you drive a RWD car!!!!!
Now, I've tried to help and I've given you some good advice. I hope you learn from it but please understand that I simply cannot help you any further and I have also lost any desire to try and help you understand once you chose to distort words and being offensive.
I wish you luck and I genuinely hope you learn about unbalanced braking from a book and not from a life experience. For all our sakes. Bye.
You've spent all this thread patronising anyone who disagrees with your viewpoint, but struggle to reflect upon your own contradictory statements (oh noes, don't use engine braking, you'll die).We get that you don't understand but instead of resorting to insults and childishness why not have an ounce of dignity and go and educate yourself on something that may transpire to be rather beneficial to you as you drive a RWD car!!!!!
Now, I've tried to help and I've given you some good advice. I hope you learn from it but please understand that I simply cannot help you any further and I have also lost any desire to try and help you understand once you chose to distort words and being offensive.
I wish you luck and I genuinely hope you learn about unbalanced braking from a book and not from a life experience. For all our sakes. Bye.
I was very patient explaining some very basic comparisons of the forces applied by engine braking and conventional statements, you didn't like that one bit (none of it was acknowledged or seemingly sank in) and continued with the hystrionics that other people have also commented on.
I know people who don't get to say anything authoritative in their real lives come on here to drone on endlessly about their point of view even if it's immature and seemingly lacking any nuance or genuine understanding.
I've been trying to help you come down from your paranoid state, I just give up.
<session terminated>
Assume the following:
.....you are not a nob dropping 3 gears and the clutch sharply
.....you are not racing on a constant (readable) surface
.....you are not in a Citroen
.....you do not have a puppy stuck to your wheel.
When looking at forces you have to take into account the source of said force and the method/speed/control of the application of said force.
Forces from handbrakes are applied totally differently than those of engine braking as well as from different points of the turning mass.
The results are thus applied to the "grip" surface in a differing manor with differing results.
In reality, if you can unsettle your car that much with engine braking your not the best driver are you ? or you have just cocked it. The fact you can do it is not argued, why you are getting it is pointing back at you.....see above
.....you are not a nob dropping 3 gears and the clutch sharply
.....you are not racing on a constant (readable) surface
.....you are not in a Citroen
.....you do not have a puppy stuck to your wheel.
When looking at forces you have to take into account the source of said force and the method/speed/control of the application of said force.
Forces from handbrakes are applied totally differently than those of engine braking as well as from different points of the turning mass.
The results are thus applied to the "grip" surface in a differing manor with differing results.
In reality, if you can unsettle your car that much with engine braking your not the best driver are you ? or you have just cocked it. The fact you can do it is not argued, why you are getting it is pointing back at you.....see above
Edited by Stickyfinger on Thursday 30th July 16:45
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