ADUK Archive

Engine momentum is pretty insignificant. When you rev the engine hard in neutral, then come off the gas, how long does it take for the revs to drop?

The slowing down or speeding up effect of the engine is largely irrelevant in the sense that modern brakes have more than enough power to lock all four wheels. I believe the issue is that having the drive connected can interfere with the efficiency of the ABS under certain circumstances. Against that you have to balance the fact that if as a situation develops you have to do anything other than full braking, this may be more awkward with the clutch down - e.g. you can't quickly get back on the power, you may miss being able to brace yourself with your left foot, and if you are going to crash you probably don't want your feet on the pedals at impact.

turnerburner666 wrote: The engine has momentum at whatever revs it is turning. Under breaking the discs will have to work harder to stop the momentum of the car AND the engine if the clutch is left depressed until the last minute

Your argument does not take account of the retardation due to engine compression which will more than cancel out engine momentum. With the clutch up the engine retardation actually increases breaking (albiet with modern brakes the extra braking effect is minimal).

gfoot wrote:Engine momentum is pretty insignificant. When you rev the engine hard in neutral, then come off the gas, how long does it take for the revs to drop?

Hmm i agree with this but it does vary from car to car. Take an old(ish) bmw for example, a T reg 320 or something...the inline 6 cylinder is a bit sluggish on revs but the breaks are more than capable of it at maximum breaking force...

But yeah, i also take zadocbrowns statement that you definitely don't want your feet on the pedals on impact...especially if you're driving a freelander around the V reg age!

Aaarrrggghhh,

Could we please spell BRAKES correctly.

When I was a much younger cars did not have servo assisted brakes nor abs and the brake differential was 2 slave cylinders in the front drums (= two leading shoes) and a single cylinder in each rear drum ( modern cars have a controlling valve often linked to the rear suspension to control the amount of force delivered to the rear brakes). You had to brake first and press the clutch just before stalling in order to avoid the back wheels( rear wheel drive back then) from locking and potential loss of control, this would also be part of the origin of the BGOL.

With today's modern cars, mostly front wheel drive and all having sophisticated braking and control systems it would be more appropriate to press the clutch immediately after the brakes ( comments about costing for a fraction of a second would be relevant but maybe not very significant to the eventual outcome)

exportmanuk wrote:When I was a much younger cars did not have servo assisted brakes nor abs and the brake differential was 2 slave cylinders in the front drums (= two leading shoes) and a single cylinder in each rear drum ( modern cars have a controlling valve often linked to the rear suspension to control the amount of force delivered to the rear brakes). You had to brake first and press the clutch just before stalling in order to avoid the back wheels( rear wheel drive back then) from locking and potential loss of control, this would also be part of the origin of the BGOL.

With today's modern cars, mostly front wheel drive and all having sophisticated braking and control systems it would be more appropriate to press the clutch immediately after the brakes ( comments about costing for a fraction of a second would be relevant but maybe not very significant to the eventual outcome)

I remember my Morris Minor 1000 having that system.

Would the fact that cars were much less powerful and had lower gearing also be a reason why it was advised to depress the clutch just before stopping?

fungus wrote:

exportmanuk wrote:When I was a much younger cars did not have servo assisted brakes nor abs and the brake differential was 2 slave cylinders in the front drums (= two leading shoes) and a single cylinder in each rear drum ( modern cars have a controlling valve often linked to the rear suspension to control the amount of force delivered to the rear brakes). You had to brake first and press the clutch just before stalling in order to avoid the back wheels( rear wheel drive back then) from locking and potential loss of control, this would also be part of the origin of the BGOL.


I remember my Morris Minor 1000 having that system

I don't recall my Moggy convertable actually having any brakes
And if it did was it not always the case that at least one cylinder was guaranteed to leak causing the brakes to pull to one side

I also drove a Ford 100E once which still had cable brakes, then it didn't matter which pedal was depressed first you still had to pray as well (keeping both hands on the wheel of course)

chriskay wrote:

fungus wrote:Aaarrrggghhh,

Could we please spell BRAKES correctly.

Yes, thanks for the reminder; although sometimes the other spelling may be more appropriate, given some of the driving I frequently witness.

whoops my bad...

A lot of modern cars particularly turbo diesels have huge amounts of low down torque which will act against the brakes unless the clutch is depressed.
At the low speeds such stops are done it makes simple sense to put both pedals down together.