Moron in a Silver Mondeo - Road Rage

[Dieselman]

Good points. The reason heavier cars have bigger brakes is, as they are heavier (aids tyre grip) and the tires are usually wider, they can apply more braking power before locking the wheels. Doesn't mean they will stop faster than smaller, lighter cars. Good tyres are most critical imho.

The real reason heavier vehicles have larger brakes is so the disk can absorb more heat before the pads over-heat.
Heavy disks reduce stopping power due to adding rotational mass.

 

[balge]

But that's the whole point, if you want to stop quickly but don't care where your car ends up it doesn't matter, but if you want to be able to avoid things like trees, lamp-posts and other cars the ABS will allow you to do it.
Without ABS one of the wheels will lock up before the others and send you lurching off in a random direction...ABS may not be as good in a straight line under ideal conditions but in the real world the ability to avoid obstacles while braking hard on variable surfaces is worth it
A good and experienced driver in good form may be able to outbrake a similar ABS car, but ABS allows ordinary drivers in panic situations (eg real life) to brake more safely.
It's a safety feature and it's safer to be in control of the car...

Although I wouldn't want to argue with the evidence of a video game simulation of a 1980's double decker bus...

 

[Ierton]

As I've already explained, larger brakes are able to maintain the point of peak retardation faster and for longer (due to thermal efficiency) than smaller brakes in an ABS system. If you put the Peugeot's brakes on the 911 what do you think will happen? Will the 911 stop in the same distance?

 

[Dieselman]

But that's the whole point, if you want to stop quickly but don't care where your car ends up it doesn't matter, but if you want to be able to avoid things like trees, lamp-posts and other cars the ABS will allow you to do it.
Without ABS one of the wheels will lock up before the others and send you lurching off in a random direction...ABS may not be as good in a straight line under ideal conditions but in the real world the ability to avoid obstacles while braking hard on variable surfaces is worth it
A good and experienced driver in good form may be able to outbrake a similar ABS car, but ABS allows ordinary drivers in panic situations (eg real life) to brake more safely.
It's a safety feature and it's safer to be in control of the car...

Although I wouldn't want to argue with the evidence of a video game simulation of a 1980's double decker bus...

Pick any test you like.
ABS increases stopping distances due to constantly releasing the brakes and re applying them, but does (as you say), allow control to be maintained.

My first car with ABS (Honda Accord) nearly caused me to have a heavy crash due to the over long stopping.

 

[Dieselman]

As I've already explained, larger brakes are able to maintain the point of peak retardation faster and for longer (due to thermal efficiency) than smaller brakes in an ABS system. If you put the Peugeot's brakes on the 911 what do you think will happen? Will the 911 stop in the same distance?

It will stop quicker until the brakes overheat due to repeated applications.

You seem to be confused about the issue here. We are talking about a single brake application on the road, not a track day.

 

[Ierton]

No it won't. It will take longer to stop because even in a single braking application the ABS will not be as efficient as the standard setup on the 911.

All cars have an optimal brake size before smaller or larger discs have a negative effect in a single brake test.

 

[Dieselman]

No it won't. It will take longer to stop because even in a single braking application the ABS will not be as efficient as the standard setup on the 911.

All cars have an optimal brake size before smaller or larger discs have a negative effect in a single brake test.

You are wrong as the point of locking will still be reached, but irrespective...

That says nothing about how a heavy C63 will be able to outbrake a lighter Pug 206.

Remember.... (moment of enlightening coming)...

The Pug 106 outbraked the Porsche 911 by 31 metres at 70mph to zero.

I'll just repeat that so you understand.


The Pug 106 outbraked the Porsche 911 by 31 metres at 70mph to zero.

 

[Dieselman]

Who says Top Gear isn't an educational programme anymore?

Note the effect of adding bigger brakes....


The boys try to make an Avantime faster than an Evo part 1 (series 12, episode 3) - BBC Top Gear

 

[Simon_M]

You are wrong as the point of locking will still be reached, but irrespective...

That says nothing about how a heavy C63 will be able to outbrake a lighter Pug 206.

Remember.... (moment of enlightening coming)...

The Pug 106 outbraked the Porsche 911 by 31 metres at 70mph to zero.

I'll just repeat that so you understand.


The Pug 106 outbraked the Porsche 911 by 31 metres at 70mph to zero.

Seems like you don't understand and just enjoy arguing and making up figures to support your fictional argument.

I just watched that YouTube clip and it clearly states:
Porsche 911 - 170ft
Pug 106 GTI - 162ft


Where do you get 31 metres from, same place as your personality disorder?

 

[renault12ts]

I've just had my ABS fixed...it was totally inoperative for the past 6 months. As DM said...the brakes did feel better without the ABS, and I never missed the system. It takes quite a lot to lock up your front wheels...which, even in some heavy braking incidents, did not occur for me.

ABS allows a car to be steered in exceptional conditions where the wheels would otherwise lock up and not allow steering. But, in a straight line with both wheels locked, you will travel in a straight line.

I learnt to drive in very primitive cars and did not get ABS until I'd been driving about 17 years. ABS is one of those systems that engenders false security.

Yes I know the thread is not about ABS...but DM is not wrong and some of you just love jumping up and down. No matter what the car...you will be able to lock the wheels or activate the ABS...then it's down to the tyres not the brakes.

 

[Dieselman]

Seems like you don't understand and just enjoy arguing and making up figures to support your fictional argument.

I just watched that YouTube clip and it clearly states:
Porsche 911 - 170ft
Pug 106 GTI - 162ft

I'll admit to not paying enough attention to the figures generated, but it's good to see you finally climb down and accept the Pug does indeed stop quicker than the almighty Porsche. (your figures, not mine)

How can that be when it has smaller brakes...??

 

[balge]

Pick any test you like.
ABS increases stopping distances due to constantly releasing the brakes and re applying them, but does (as you say), allow control to be maintained.

My first car with ABS (Honda Accord) nearly caused me to have a heavy crash due to the over long stopping.

Exactly, the ABS is doing the same thing as a good driver, varying the braking to slow down as quickly as possible - but not everyone is a good driver, or not reliably good enough not to stamp on the brake as hard as they can and hold it down as if their life depended on it when confronted
with a potential crash? An expert driver might still be able to brake properly without panicking but will Mrs Miggins from the pie shop? The ABS lets her slow down more safely, at the cost of a slightly longer theoretical distance than an expert could manage, but with less risk of the car hitting anything during that fractionally longer braking period

Didn't F1 ban ABS at some point? So they had to invent carbon-fibre brakes and so forth?


http://www.monash.edu.au/miri/research/reports/other/racv-abs-braking-system-effectiveness.pdf

Interesting conclusions p34

 

[Dieselman]

Didn't F1 ban ABS at some point? So they had to invent carbon-fibre brakes and so forth?

That's not why carbon brake disks were invented, that was to save mass, thus give shorter stopping distances due to reduced rotating mass, which aptly demonstrates why bigger brakes increases stopping distances.

I remember reading some while ago about Ford Granada crash statistics and it being found that cars fitted with ABS had more crashes, pro-rata, than ones without, because the drivers still didn't steer round the obstruction and the longer stopping distance caused the car to fail to stop in time.

Without doubt ABS is a nice comfort feature as it gives surety against locking the wheels.

 

[Dieselman]

I've just done a quick calculation of how much Kinetic energy each car mentioned has at 80mph.

(I take it you know what kinetic energy is? )

Pug 206 = 621,000 joules

C63 = 1,075,000 joules

Ignoring that the tyres will have a similar coefficient of friction so similar grip levels, EVERYTHING on the C63 has to work 1.73 times better for that car to have the same braking ability as the Peugeot 206.

That means the brakes have to provide at least 1.73 times better stopping ability (which they can't because the Pug can lock the wheels), the suspension has to control the wheels and stop weight transfer at least 1.73 times better, and the tyres have to grip at least 1.73 times better.

 

[Simon_M]

I'll admit to not paying enough attention to the figures generated, but it's good to see you finally climb down and accept the Pug does indeed stop quicker than the almighty Porsche. (your figures, not mine)

How can that be when it has smaller brakes...??

Christ you are so tedious, I am not climbing down, I never said the Pug GTI would not stop quicker than the 911 - it's in the video! Please quote me when I said that.

When will you finally climb down from your own ar$ehole ?

 

[Dieselman]

I am not climbing down,

I guessed you wouldn't...

Did you do science at school?

 

[Ierton]

You are wrong as the point of locking will still be reached, but irrespective...

Respectfully it is you who are wrong. The point of locking is not hard to reach with any braking setup. What is hard is repeated applications of the pad to disc to maintain peak retardation (maintaining hysteresis and not entering a state of dynamic friction). A larger disc and caliper means the rate of reaching and maintaining this can be greater (the frequency of ABS pulses is higher) and so more time is spent at peak retardation. The Peugeot ABS system will cycle at a different maximum rate to that of the Porsche because it's been designed to work with a specific size of caliper and disc size. This may or may not be the optimal setup for the car as it will be manufactured to a price.

Either you don't understand this or you don't want to but it's a material fact. Larger discs and calipers can (but not always) offer better one-time braking performance than standard.

 

[Dieselman]

Larger discs and calipers can (but not always) offer better one-time braking performance than standard.

As aptly demonstrated in the Top Gear, Avantime video... After all, those £3000 larger brakes only lost 2.1 seconds per lap against the cheapo Renault ones.

I would be extremely dubious about the ABS cycles being more frequent due to fitting larger brakes when all logic says the added mass reduces the ability of the wheel to react as quickly.

Do you have any data to bolster your claim?

 

[Simon_M]

I guessed you wouldn't...

Did you do science at school?

That's probably where you are going wrong - you should really have been studying Physics and Mathematics to learn about mechanics, so if you want to get clever you should be factoring in fuel levels, passengers - but you've already accepted you don't pay attention. Maybe you stared out the window too much during your 'science' lessons at school....

Do you have any data to bolster your claim?

That's never stopped you in the past.

 

[Dieselman]

That's probably where you are going wrong - you should really have been studying Physics and Mathematics to learn about mechanics, so if you want to get clever you should be factoring in fuel levels, passengers - but you've already accepted you don't pay attention. Maybe you stared out the window too much during your 'science' lessons at school....




That's never stopped you in the past.

Where is your data and calculus? As usual, there isn't any, just insistent argument.


To repeat:

The Pug 106 outbraked the Porsche 911.

When adding larger brakes to the Avantime it was slower due to higher rotational mass and no additional braking effect, because the point of locking could already be reached.

The TG team regained most of the lost 2.1 seconds by fitting sticky track tyres...which is where this discussion started. Tyres are what improves stopping distances, not brakes.
They then gained time by installing better suspension, but mostly by reducing mass.

Which bits of that don't you understand and I'll try to dumb it down a bit further for you.