Simultaneous Application of Gas and Brake Pedals
 

Nomen Nescio wrote:

> Now look at a modern car. The brake and accelerator pedal have
> little or no difference in height. Is is entirely possible for
> the right foot to press on both pedals at the same time.

The heavy duty floor mat (Mopar brand, which I use in the winter) in
my 300M tends to creep forward and up against the center console -
which means it gets up and behind (and to the right) of the
accelerator pedal. This reduces the amount of foot-space to the
immediate right of the accelerator pedal and moves the right foot a
little to the left instead of being centered on the accelerator
pedal. I've found that in this position I brush against the *back* of
the brake pedal when pulling back on the gas.

All in all I'd have to agree that there should be more spacing between
the gas and brake pedal.

But I think that it's a manditory design criteria that the brake
system of any car is supposed to be able to over-power the engine in
all situations. Back in the days when you had a spring that pulled
back on the throttle plate, if that spring broke you could have WOT
(wide-open-throttle). I can't imagine the braks system of any car not
being able to stop the wheels from turing - even in that situation.

Couldn't in my 1967 GTO. The engine torque far overpowered any brake
pressure I could place on the brake pedal. Now the car wouldn't actually
move (the front brakes kept it in place)...but it would sure billow plenty
of smoke from the spinning rear tires!

On Sat, 22 Jan 2005 22:38:54 -0500, "James C. Reeves"
> wrote:

>
>Couldn't in my 1967 GTO. The engine torque far overpowered any brake
>pressure I could place on the brake pedal. Now the car wouldn't actually
>move (the front brakes kept it in place)...but it would sure billow plenty
>of smoke from the spinning rear tires!
>
And if it had been front wheel drive?
That's the rub with many of todays high powered vehicles. You have
antilock brakes that are made as small as they can get away with to
keep the weight down (and since they have antilock, it is hard to
overwork them anyway) and now we have cars with more horsepower than
the old muscle cars. The power brakes are engine vacuum operated, and
the vacuum goes for a dump when the engine is under load.

So, yes, there are MANY cars on the road today that would have a hard
time restraining the engine with the brakes even well below full
throttle.

> wrote in message
...
> And if it had been front wheel drive?

Isn't more braking power put to the front wheels of a car due to the weight
distribution properties during stoping? I don't know the ratios, though.

> That's the rub with many of todays high powered vehicles. You have
> antilock brakes that are made as small as they can get away with to
> keep the weight down (and since they have antilock, it is hard to
> overwork them anyway)

How do you figure? Antilock does not help with heat tolerance or
dissipation.

> and now we have cars with more horsepower than
> the old muscle cars. The power brakes are engine vacuum operated, and
> the vacuum goes for a dump when the engine is under load.

Yes, but you should still have pressure for at least a couple brake presses
stored up in the system - same as if the engine stops while driving.

--
Scott Ehardt
http://www.scehardt.com

On Sat, 22 Jan 2005, James C. Reeves wrote:

> Couldn't in my 1967 GTO. The engine torque far overpowered any brake
> pressure I could place on the brake pedal.

Well, sure, but that was when Deet-riot was still selling cars with 300
horsepower and 9-1/2" drum brakes at all four corners.

In article >,
"Scott Ehardt" > wrote:

> > wrote in message
> ...
> > And if it had been front wheel drive?
>
> Isn't more braking power put to the front wheels of a car due to the weight
> distribution properties during stoping? I don't know the ratios, though.

Yup, the ratios are appx 85/15 for FWD and appx 60/40 for RWD

> > That's the rub with many of todays high powered vehicles. You have
> > antilock brakes that are made as small as they can get away with to
> > keep the weight down (and since they have antilock, it is hard to
> > overwork them anyway)
>
> How do you figure? Antilock does not help with heat tolerance or
> dissipation.
>
> > and now we have cars with more horsepower than
> > the old muscle cars. The power brakes are engine vacuum operated, and
> > the vacuum goes for a dump when the engine is under load.
>
> Yes, but you should still have pressure for at least a couple brake presses
> stored up in the system - same as if the engine stops while driving.

Correct, there is a vacuum check valve in the booster inlet that
should prevent the vacuum from dumping out when the engine is
under load. It usually takes between 8 and 10 (and sometimes
more) pedal pumps to deplete the stored vacuum in a brake booster
with the engine not running.

Well said.
I would also submit that this mysterious sudden application of
throttle is likely only reported in cars with automatic transmissions,
since the resultant crash would probably be avoided if one foot was on
the clutch--i.e. the person backing up (in this case) and experiencing a
sudden racing of the engine would instinctively stomp the clutch and get
the vehicle stopped, perhaps more slowly since some of the pressure is
on the throttle as well as of the brake...you get the idea.

Then the driver would look down and realize what was happening, and
take their foot off the accelerator, hence there'd be no accident to
leave them all dazed, confused, and fully convinced that the "engine
just raced unexpectedly" --since after an ordeal like that many people
are often somewhat traumatized and don't really have a clear idea what
the hell just happened.
Just my 2=E7.

BTW I'm new to this forum, very interesting & informative.

"Daniel J. Stern" wrote:

> Well, sure, but that was when Deet-riot was still selling cars with
> 300 horsepower and 9-1/2" drum brakes at all four corners.

300 HP not necessarily at the wheels. Even 300HP was exaggerated.

Drum brakes are more efficient (hydraulically speaking) at braking
than disk brakes. Way more surface area too. But more prone to fade
(which does not come into play in the current context).

On Sun, 23 Jan 2005 05:18:01 GMT, "Scott Ehardt"
> wrote:

> wrote in message
.. .
>> And if it had been front wheel drive?
>
>Isn't more braking power put to the front wheels of a car due to the weight
>distribution properties during stoping? I don't know the ratios, though.
>
>> That's the rub with many of todays high powered vehicles. You have
>> antilock brakes that are made as small as they can get away with to
>> keep the weight down (and since they have antilock, it is hard to
>> overwork them anyway)
>
>How do you figure? Antilock does not help with heat tolerance or
>dissipation.
>

No, but because antilock brakeswork smoother if they don't lock in the
first place, manufacturers tend to install smaller less effective
brakes on cars with antilock as standard.
>> and now we have cars with more horsepower than
>> the old muscle cars. The power brakes are engine vacuum operated, and
>> the vacuum goes for a dump when the engine is under load.
>
>Yes, but you should still have pressure for at least a couple brake presses
>stored up in the system - same as if the engine stops while driving.