Brake Pedal Force: Approximation

[vinay ks]

what is the approx brake pedal force that a person applies while braking on the brake pedal?

 

[Ranger Mike]

drum brakes or disc brakes which have power booster?

 

[jack action]

Usually, with manual brakes, you set up the brake system such that you need a pedal force no more than a 100 lb per g of deceleration.

A booster may divide easily the pedal effort needed by a factor of 2. (more info here)

 

[vinay ks]

disc brakes

i want to know for disc brakes. 100 lbs is a large force! can a person apply that much of force while he is seated on the pedal? i want to know how a person who is about 130 to 150 lbs apply that amount force??

 

[Ranger Mike]

Typical race car brake pedals have 3:1 mechanical advantage and some production automobiles have up to 8:1 mechanical advantage.
The most common pedal IS 6:1 so if you apply 100 pounds force to the pedal the input force to the master cylinder is 600 pounds.

So you see a slight amount of input force will be translated into a huge amount by the linkage to the master cylinder. I had a brake pressure gage on an old race car one time and it read up to 1500 PSI for the hydraulic brake fluid pressure. More than enough to stop a passenger car.

 

[jack action]

i want to know for disc brakes. 100 lbs is a large force! can a person apply that much of force while he is seated on the pedal? i want to know how a person who is about 130 to 150 lbs apply that amount force??

According to NASA, with the proper position, you can go as high as 2500 N or around 560 lb (a 100 lb is 445 N):

 

[SteamKing]

The leg muscles are some of the largest in the body. It is quite easy to generate 100 lb of force with one leg. After all, your legs keep you from falling down.

 

[Kozy]

Go and put some bathroom scales against the wall in a corridor, sit on against the opposite wall and push on the scales with your right foot. That'll give you some idea of what is reasonable. I can assure you, 100lbs is not 'normal' braking in a modern passenger car!

I challenege anyone to generate 560lbs too. Maybe an F1 driver in an F1 car capable of braking at 3g (additive force from decelleration), but not an average driver in a normal road vehicle. Not a chance.

 

[xxChrisxx]

Is there any reason you've taken two posts out of context?

Go and put some bathroom scales against the wall in a corridor, sit on against the opposite wall and push on the scales with your right foot. That'll give you some idea of what is reasonable. I can assure you, 100lbs is not 'normal' braking in a modern passenger car!

One might also say that 1g is not 'normal' braking. It's a rough rule of thumb of a limit of input force.
Everyone should be able to apply that force, and passenger cars will lock the wheels before 1g.

So in essence the rule is saying that the 'average' person should be able to apply a force sufficient to lock the wheels.

I challenege anyone to generate 560lbs too. Maybe an F1 driver in an F1 car capable of braking at 3g (additive force from decelleration), but not an average driver in a normal road vehicle. Not a chance.

That is a capability of 'a leg' at certain angles. The practicality of doing so is neither here not there.

The whole thread is off to a bad start because the question isn't defined properly. With such a range of servo assistance and pedal ratios and brake types, you can pick almost any figure you want. It's like asking "what is the average amount of steering lock to go round a corner".

It's such a ill defined question that it borders on meaningless.