HP of brakes to engine HP, 3 to 1?

Brakes are designed to overpower the engine.
What is the ratio of 'HP of brakes' to 'engine HP' in designing a brake system? Is it 2 to 1, 3 to 1, or other?
i.e. with a 3 to 1 ratio, 100 horsepower engine, the brakes will be capable of developing an effective 300 horsepower.
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Dunno. How many seconds does it take for you to get up to 60 mph from a full stop? How many seconds does it take for you to get to a full stop from 60 mph?
In the case of braking the tires and the road surface are more of a limiting factor today than the brakes. --scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

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On 2 Mar 2010 02:06:09 GMT, snipped-for-privacy@FreeNet.Carleton.CA (M.A. Stewart) wrote:

Keep in mind that the engine is designed to put out maximum power for a considerable length of time. The brakes are only designed to consume their max power for only a very limited period of time before they overheat. I think that's why you hear so many people say "the brakes didn't work". They worked but only at first. If you don't get it stopping the FIRST time you try you wind up cooking them.
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Ashton Crusher wrote:

This could be a downside of anti-skid systems. If you lock up the brakes, they then do not dissipate much energy. The energy is then dissipated at the tire/road surface. So if you can LOCK the brakes right away, you overcome the fade problem.
Can't do that with anti-skid brakes, you'd need to turn AS off.
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On Tue, 02 Mar 2010 08:55:35 -0600, Don Stauffer

I agree and think that is one of the major reasons people have had trouble stopping cars with throttles stuck open.
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M.A. Stewart wrote:

Brakes work on a very simple principle, friction. They do not develop power they simply convert energy. Most common brakes attempt to stop motion by converting that motion into heat. The problem then becomes, How fast and how much heat can the brakes dissipate before they reach thermal overload and fail. They are also not designed for continuous input of energy.
Engine HP has very little to do with brake design. Overall weight/mass of the vehicle, it's probable payload and any towing capacity it has are where you start in brake designs. Then you start with swept area, pad materials, rotor materials, additional venting and airflow to provide cooling.
Now with all the materials out there you need to balance the characteristics as well. Nice soft pads will convert the energy faster BUT they won't wear well and the higher heat generated will be harder to dissipate. Harder pads will wear better but may damage other components due to higher pressures required to make them work.
Drum/rotor materials are another fun area. A nice thin vented rotor will cool faster and allow better braking BUT it will also warp faster. Thicker non vented rotors won't warp but will increase unsprung weight and affect handling. They also will cause more heat to be retained in the rotor which will increase brake fade.
Overall thermal mass of the braking system also has a HUGE effect on braking. The size and composition of the hub, rotor, brake mounting, rim material and venting all play a part in this. Combine these items with available air flow and it gets interesting really quick.
Here is a scenario for you. Take a typical small light car, like a Neon or Corolla. Neither one is very heavy. They both are passenger only vehicles with no real tow rating. Start with the original car and add a set of very open lightweight aluminum rims. Now add the typical spoilers and body kits and lower the car. What do those items do to braking? Most people figure they do nothing. However the lowered vehicle decreases the available air to the back of the brakes. The open rims may increase the air flow to the face of the rotors. The spoilers and body cladding will disrupt the airflow even more. What is the end result? People start complaining about brake fade and how they HAVE to upgrade the brakes.
In the case of the brakes on the cars with bad accelerator pedals. I read all the time in the different groups about how much better the brakes on the imports are, that they last longer and that they don't suffer the warped rotors and pulsing that are "common" to the domestics.
These comments tell me that the rotors are likely minimally vented if at all, that the pads are made of a harder material and that the thermal mass of the assembly is lower overall. Doesn't sound bad until you consider those items against brake fade. Lack of venting and harder pad materials mean a higher chance of fading. Lower thermal mass means they do not have extra capacity to store the heat generated until it can be evenly dissipated.
Now look at the claims most of the people are voicing. "The gas pedal was stuck, the engine was revving and holding the brakes down didn't stop the car" Textbook definition of brakes that have stopped operating due to heat overload. I would bet that if you pulled the brakes apart on one that had this problem you would find a few things. 1 - brake pads that crumble and backing plates that are blued from the heat. 2 - rotors that looked very highly polished and smooth, this will be due to the high heat and friction combining to planish the metal smooth. 3 - calipers with scored bores and damaged seals due to the higher heat causing the pistons to expand and lock in the bore. 4 - brake fluid that has changed due to the higher heat causing chemical changes. 5 - probable damage on the inner side of the tire from the heat generated from the brakes.
--
Steve W.

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First time I have ever heard/read of HP of brakes. Disk brakes work similar to caliper brakes on bicycles. http://www.bikewebsite.com/bicycle-bra.htm Drum brakes are the old fashioned brakes. cuhulin
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On Mar 1, 6:06 pm, snipped-for-privacy@FreeNet.Carleton.CA (M.A. Stewart) wrote:

They are apples and oranges.... marathon runner and sprinter Ben
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