Emergency braking - dip the clutch?

[Jim]

ABS will save your life, if it's employed within it's limitations. It WILL stop you sliding if you have panicked and mashed both feet on the pedal, which ALL of us will have happen to us no matter how much training, experience or confidence we have.

HOWEVER

It will NOT stop you in a sideways slide, it will NOT stop you in time if there is physically not enough braking distance available before impact.

It's a good thing, but it's not foolproof and it should not be a substitute for good driving habits. "It's OK, I have ABS" should be a solid warning sign to never get in the car with whoever just uttered it.

Alternatively, "ABS is shit, I can brake better without it" is in the same category.

[dazza]

I normally have the clutch in before I even think about hitting the brakes - my first reaction

[tandy ass]

I can recall in my old R32 GTS4 that in a straight line I could stop in about the same distance, wet or dry, with or without the assistance of ABS.

However in a corner, there wasn't a hope in hell of maintaining sufficient braking with ABS switched off. You either locked the inside wheels and assisted a spin or just coudln't stop quickly enough. With ABS on, you could stop a good 20-30% shorter distance since you simply mashed the stop pedal and all four wheels would deliver maximum braking and the car wouldn't end up in a spin.

For the comedian suggesting to change down gears in an emergency stop, thanks for providing me some humour to an otherwise boring drab day.

Its good to see in the two seconds or so in a panic stop from say 60 or 80km/h, you dont need to use your left foot to brace yourself to be able to modulate the brakes to prevent lockup in a non ABS car, or in an ABS car, you're using your right foot which does the braking to brace yourself. Oh and yeah, you also are capable of controlling compression lockup of the rears that will happen if you downshift.

Give me a break. Emergency stops require focus and the fewer things you have to do NOT related to stopping, such as changing gears, the quicker you will stop.

Besides, if you aren't exceeding the speed limit, nothing will ever run out in front of you nor will you ever have a need to emergency brake.

[Fatboy]

As a race driver i feel i should add my thoughts here - I just close my eyes and hold on. Usually by the time it's over i've done more spins than Kylie Minogue and hopefully didn't hit anything in between. Hope this helps...

P.S - Race situation, clutch in. Mainly to get going again asap but the lack of inertia thing makes sense too...

[Cplus]

If you know how to drive you down change while under heavy braking to take advantage of the engine braking as well without locking the rear wheels. Not good for the average joe though cause 90% of the time he will lock the wheels

WRONG.

we had this arguement a few years back an resulted in me getting a phone call from Mark Scaife with the answer.

if you don't believe me watch anyform of decent racing with a H pattern gearbox. Engine braking does not help you stop faster, it will however make your pads last longer.

Gears are for Going.

Brakes are for Braking.

Cheers,

C+

[rowdytoot]

but we all know skaife can't drive for shit, don't we C+!!!!!!

Rowds

[Cplus]

yeah he's rubbish compared to most of the blokes on this forum.

[Jim]

yeah he's rubbish compared to most of the blokes on this forum.

:rotflol:

[BigMuz]

You guys are all wrong, without engine braking we would cook brakes all the time.

We are talking about prime movers with exhaust brakes aren't we?

Sheesh.. 02pruv has a lot to prove now...

Muz

[barM3]

See what you guys think of this and feel free to comment.

On emergency braking:
In a real emergency stop I don't think you should clutch in. There are two main reasons. 1) Your mission is to stop in as small as distance as possible. The risk of stalling is not a priority because you basically just want to pull up in the shortest distance possible and/or avoid an object. 2) When you brake heavily, where does your weight go? Forwards of course. Unless you're strapped into a harness (and we're talking road cars here), your weight will go onto your feet and hence make it hard or impossible to modulate pressure on the pedals. In modern cars with power-assisted, good quality brakes, you can apply enough pressure with just your index finger on the pedal to lock them. So the idea is to use your left leg as a brace. In normal driving your left foot should always be on the foot rest and so in all types of braking you should apply some pressure onto the foot in order to push your body back into the seat. Your right foot should never leave the floorpan anyway, and should just rock on the heel between throttle and brake, so your heel should be on the floor. You now have a stable base to work from. You should begin braking with a light 'brush' on the brake pedal to settle the car. This is done by using only your little toe which allows the car to settle on its suspension rather than standing on its nose, giving you a more equal balance of tyre contact patch on all four corners (after all tyres stop the car, not brakes). You should then proceed (once the car is settled) to roll from the little toe to big toe to increase pedal pressure and progressively bury the pedal to make a full-force stop. Only in the last few meters should you take your foot of the footrest (which has until now been acting as a brace and allowing you to modulate braking pressure with your right foot) and depress the clutch. If you are too late and stall, it doesn't matter, because your main objective has already been accomplished.

On ABS:
ABS in great because it allows you to steer as well as brake in a manner that the majority of people can't do on their own. You should be able to stop a car in as short a distance (or shorter) without ABS than with ABS (in ideal conditions which includes not panicking). People think that by stomping on the pedal you make a quicker stop than by doing the brush and bury technique that I mentioned, but that's not the case. You may sacrifice a bit of initial braking force, but you end up with a better balanced car that will stop much quicker at the other (business) end of the stop. Like others have mentioned you're still carrying nearly half your speed in the last few meters.

[bahaimus]

ie "in the last 5m of braking, you wipe off half your speed"

??? how does that ford vs ford anti-speeding ad say?

kewl so if I'm doing 100 km/hr 5 metres out, I'll only be doing 50 when I hit.. wow!..sweet... I'll have to rememver that ! yes this is sarcasm, and lack of context posting.. - I know you are doing the same tinkerbell :D:D

The ads might be taking liberties a bit, but what they are saying is in effect true.

Just this weekend gone I was out Mt Cotton training centre in Brisbane and witnessed a braking exercise by a WRX with ABS. Braking at the same point, from 40km/h it stopped in just over its body length. At 60km/h it was double the distance. What is going on here? It takes the first body length to wipe off the top 20km/h and then takes off the next km/h in the second body length.

Can't argue with a graphic demonstration like that.

So, are the ads lying?

[rowdytoot]

yes I think they are; it gives the impression that no matter what speed you are doing you lose 1/2 of it in the last 5 metres...for joe Public I think that's a dangerous assumption- surely it encourages tailgating and late braking...?!

JP will expect to wipe off lots of speed in the last little bit no matter what speed the start braking from.. it don't work that way.. if you'd doing eleventy billion km/hr when you get to that last little bit b4 impact, you'll still be going too fast when you hit!

I do have a fair grasp of the physics behind it- can't be arsed getting out the graphics calculator though ! :D:D

Sweeping generalisations like that only further discredit the campaigns that monash put out on behalf of the gumbyment! not that I think they've got much cred. at all!..

Rowds

[rj-astra]

The best thing you can do with ABS is make sure it works, then forget you have it.

That's why manufacturers are implementing Brake Assist (BA). Make sure joe public uses maximum braking pressure in an emergency.

[tinkerbell]

In modern cars with power-assisted, good quality brakes, you can apply enough pressure with just your index finger on the pedal to lock them.

barM3 - let me know where i can get some of the shit the guy who wote this is on!

[tinkerbell]

The ads might be taking liberties a bit, but what they are saying is in effect true.

Just this weekend gone I was out Mt Cotton training centre in Brisbane and witnessed a braking exercise by a WRX with ABS. Braking at the same point, from 40km/h it stopped in just over its body length. At 60km/h it was double the distance. What is going on here? It takes the first body length to wipe off the top 20km/h and then takes off the next km/h in the second body length.

Can't argue with a graphic demonstration like that.

So, are the ads lying?

i have actually participated in (not jsut witnessed) such scenarios (at HART and at EC skidpan).

brake at a point (known) and stop ASAP

from 40, 60, 80km/h

with full ABS and also trying not to engage ABS... it is good way to appreciate the distance as witches hats are usually palced where you stop...

it is like:


S_40____60____________80

the ads are right/correct but are potentially misrepresenting the actual circumstances to Joe public...