Brake Pedal Force: Approximation

In summary, the amount of force applied to the brake pedal varies depending on the type of brakes and the use of a power booster. With manual brakes, the pedal force is typically set to no more than 100 lbs per g of deceleration, but a power booster can reduce this by half. For disc brakes, the average pedal ratio is 6:1, meaning that 100 lbs of force on the pedal translates to 600 lbs of force on the master cylinder. It is possible for a person of average weight to generate this amount of force with one leg, but it is not a normal amount of force for braking in a modern passenger car. In some cases, such as an F1 driver in an F1 car,
  • #1
vinay ks
8
0
what is the approx brake pedal force that a person applies while braking on the brake pedal?
 
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  • #2
drum brakes or disc brakes which have power booster?
 
  • #3
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)
 
  • #4
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??
 
  • #5
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.
 
  • #6
vinay ks said:
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):

Image137.gif
 
  • #7
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.
 
  • #8
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.
 
  • #9
Is there any reason you've taken two posts out of context?

Kozy said:
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.
 

1. What is brake pedal force?

Brake pedal force is the amount of pressure required to push the brake pedal down and engage the brakes of a vehicle.

2. How is brake pedal force measured?

Brake pedal force can be measured using a dynamometer, which is a device that measures the amount of force applied to the pedal. It can also be calculated by measuring the force applied to the brake pads and dividing by the pedal ratio.

3. What factors affect brake pedal force?

The main factors that affect brake pedal force are the type of brake system, the size and weight of the vehicle, and the condition of the brake components such as the brake pads and rotors. The pedal ratio, which is the length of the pedal arm compared to the length of the master cylinder push rod, also plays a role in determining the required force.

4. Why is it important to approximate brake pedal force?

Approximating brake pedal force is important for designing and testing brake systems in vehicles. It allows engineers to determine the optimal pedal ratio and brake system components to provide efficient and safe braking performance. It also helps in identifying potential issues with the brake system that may require adjustments.

5. How can brake pedal force be reduced?

Brake pedal force can be reduced by using a power brake booster, which uses engine vacuum to assist in applying the brakes. This reduces the amount of force required to push the pedal. Other methods include using a larger pedal ratio or upgrading to more efficient brake components such as larger brake pads or ventilated rotors.

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