The Truth about FOX FRONT BRAKES!

nito88stang · Feb 18, 2004

I think its time for ye ol

GT5.0L · Feb 18, 2004

Steel brake lines. Licoln mark VII 73MM Calipers. Steel bushings.

Will this set up work with stock size driled roter`s and stock rim`s on a 89 GT???

chaka · Feb 18, 2004

sleeper89 said:
so let me get this straight (as i'm not an engineer), you're saying that the coefficient of friction between the pad and rotor is equivalent (or very close) to the coefficient of friction between the pad and the (air in the) holes/slots? please do elaborate.

-steve

Surface Area DOES NOT affect friction. The friction force between the pads and a solid rotor and the pads and a drilled rotor are the same. Put the holes back in and the friction force will be the same. (assuming no temp. increase and the rotors are the same material and the pads are the same material)

Usually when you switch rotors you usually buy better brake pads. The coefficient of friction is now different then from the solid rotor and cheapo pads (hopefully better)

The holes are only there to provide a place for the "green gas" or whatever you call it to go when you heat the pads up. Otherwise the gas gets trapped between the pad and the rotor. Sort of like when you hydroplane there is a small film of water between your tires and the road. and your coffecient of friction is reduced. lowering your FrictionForce.

Does that make sense steve?

sleeper89 · Feb 18, 2004

chaka- i understand what you are saying about surface area not affecting the Cf, but when you replace metal rotor surface with air that would reduce the Cf, no? ie with drilling you increase surface area but decrease brake pad contact area, would that not in turn decrease Cf?

thanks

-steve

chaka · Feb 18, 2004

well the CF between the air and metal is definitly lower then the CF between the pad and the metal.

But when you say the friction force between the rotor and pad you are saying that. so it does matter about the air. The force between the rotors and pads are the same.
When you take into account the pressure the MC puts out into the brkae lines and how the brake fluid compresses and how the fluid pushes the piston and the size of the piston and then how the friction force relates to heat transfer and blah blah. So there is a lot more to braking then the friction force.

sorry for getting all ansty. just aggravating to here that friction force is affected by area. to think mustang5l5 said that. too haha

sleeper89 · Feb 18, 2004

chaka said:
The friction force between the pads and a solid rotor and the pads and a drilled rotor are the same. Put the holes back in and the friction force will be the same. (assuming no temp. increase and the rotors are the same material and the pads are the same material)

ok, this i could understand if the pad size were increased to make up for the area which is now holes. i understand that surface area doesn't affect the Cf but i would think the the bigger contact patch at any given Cf would help you to brake better by transferring more heat to the rotor.

sorry about all the technical questions, "knowing is half the battle"

-steve

edit: alright, saw your post in between, guess i got ahead of myself.

BlackFox5.0 · Feb 18, 2004

astronut1885 said:
When I swapped over however, I did notice better braking than last time I did brakes and went with stock. I had less fade and quicker stops overall. Both sides have good arguments, but I think only a road test can settle it. I personally like slotted rotors. They've worked for me, and they look nice in the wheel well too. Just my .02

Are you comparing old glazed over brakes to brand new pads and fresh cut rotors?

They only way to compare the difference is to have them both have the same mileage AND abuse put on each brakes. Even though the braking difference between drilled rotors and stock rotors is marginal, the stock brakes are still much better to go with. They are cheaper, save pad life, work more effeciently, and in many cases will not warp, and especially not crack.

The only time you should have drilled rotors is if you Road Race and make frequent high speed to low speed stops very quickly.

MustangGroupie · Feb 18, 2004

I am not reading this whole thread..... if you have a problem with warping factory rotors or brake fade, step up to drilled/slotted/dimpled rotors and this will remedy the problem. I have seen countless brand new cars (including stock corvettes) need rotors with less than 10,000 miles on the odometer......when switching to a good(good implies better) rotor with better heat dissiapating capabilitys, the problem is remedied.

93 teal terror · Feb 18, 2004

Again...Slotted,Drilled,Dimpled rotors will NOT increase stopping power better than a solid rotor (assuming there is no build up of gasses). If you are worried about gasses building up for racing buy a pad that reduces this problem a lot if not all together. All you are doing is shortening the life of your expensive brake pad when you buy drilled,slotted,dimpled rotors. Not only do you decrease the life of your brake pad, but you increase the pressure on the rotor. This is why the rotor is prone to cracking if they are not designed for the holes. Even with holes as small as 5mm you can increase the pressure on the rotor 20%. If you have any doubt ill post the calculations.

custom89stang · Feb 18, 2004

93tealterror, there is less weight and it will grab the dimples and holes better than an all flat. But as i say next.......we will find out.....

THATS IT YOU DUMB$HITS I'M CALLING MY GRANDPA (head of PHYSICS AT THE UW) and asking him. Case settled tonight.

sleeper89 · Feb 18, 2004

custom89stang said:
THATS IT YOU DUMB$HITS I'M CALLING MY GRANDPA (head of PHYSICS AT THE UW) and asking him. Case settled tonight.

good for you junior, maybe he can give you some manners at the same time. let us know what you find out.

-steve

Mustang5L5 · Feb 18, 2004

custom89stang said:
93tealterror, there is less weight and it will grab the dimples and holes better than an all flat. But as i say next.......we will find out.....

.

How do these holes grab better? Explain this to us.

And answer this...if the holes allow you to grip better, why don't we drill our flywheels? Why did i go spend $$$ for a high performance clutch to increase grip when i would have just whipped out my trusty sears 18V cordless and went to town on my flywheel. I mean if your "holes in rotor increase grip" thoery is true, it should work on flywheels too right?

You've said this about 5 times already so why don't you explain it to us why holes in rotor increase it's stopping ability. Feel free to use as little actual fact as possible.

BlackFox5.0 · Feb 18, 2004

I don't care if you invented psyhics. Real data comes from the field. I'm just speaking for all the road racers here, and they WILL (and have already) agree with me. Stop the ignorance.

chaka · Feb 18, 2004

BlackFox5.0 said:
Are you comparing old glazed over brakes to brand new pads and fresh cut rotors?

They only way to compare the difference is to have them both have the same mileage AND abuse put on each brakes. Even though the braking difference between drilled rotors and stock rotors is marginal, the stock brakes are still much better to go with. They are cheaper, save pad life, work more effeciently, and in many cases will not warp, and especially not crack.

The only time you should have drilled rotors is if you Road Race and make frequent high speed to low speed stops very quickly.

True

chaka · Feb 18, 2004

93 teal terror said:
Again...Slotted,Drilled,Dimpled rotors will NOT increase stopping power better than a solid rotor (assuming there is no build up of gasses).

Well went to class and was thinking. So you have the force of friction turning into heat.
So now ForceFriction=MassRotor*(acceleration of Rotor). now assuming you decceleration is constant and it is is from V to 0. and without all the angular stuff.

Now the decceleration is related to the (acceleration of rotor) So the smaller the mass of the rotor the larger the (acceleration of rotor) must be which is directly related to the energy release. So they would heat up quicker, which has been proven since they are more likely to warp and crack (I know this is also in part with the holes) And why most roadracers try to route as much airflow over the brakes.

Does that make sense you physics buffs. I am a little rusty.

DirtyD916 · Feb 18, 2004

custom89stang said:
Slotted/dimpled rotors are better.

no 'Kiss Me''Kiss Me''Kiss Me''Kiss Me''Kiss Me'

DirtyD916 · Feb 18, 2004

hhaahahhaahaha wat did i just say ???????!!!!!

DirtyD916 · Feb 18, 2004

actually chaka the smaller the rotor the smaller the acceleration. the velocity or acceleration of the rotor is all dependent on what point of the rotor your measureing. is it the outside edge of the rotor or is it the center? I mean its like a merry go round, the people on the outside section of the merry go round feel the greater acceleration and under go the greatest velocity because of there further distance from the center.

Mustang5L5 · Feb 18, 2004

chaka said:
well the CF between the air and metal is definitly lower then the CF between the pad and the metal.

But when you say the friction force between the rotor and pad you are saying that. so it does matter about the air. The force between the rotors and pads are the same.
When you take into account the pressure the MC puts out into the brkae lines and how the brake fluid compresses and how the fluid pushes the piston and the size of the piston and then how the friction force relates to heat transfer and blah blah. So there is a lot more to braking then the friction force.

sorry for getting all ansty. just aggravating to here that friction force is affected by area. to think mustang5l5 said that. too haha

Ok lets try this....

F = pressure x area

F = 1000psi x 12 in^2 (rough estimate of max brake pressure and stock rotor surface area)

F = 1000 psi x 11in^2 (area of crossdrilled rotor)

Fsolid = 12000 lbs
Fdrilled = 11000 lbs

F is our normal force N

Now we use this equation Fk = Muk * N (Mu is a symbol that my computer can't generate but you engineering guys should know what i am talking about.

Fk is the frictional force
Muk is the coefficient of friction
N is the normal force from above

I have the Coeff of friction of leather on metal is 0.50. I have no idea what the actually MuK is so we will use that number since it's the closest i could find to brake pad on metal

.5 X 12000 = 6000 lbs-F (Frictional Force on solid face rotor)
.5 X 11000 = 5500 lbs-F (frictional force on drilled rotor)

I may not be 100% right on units, but that's what i have to prove that a larger contact area of a pad will give you more stopping force.

Does that check out with any of your other engineering/physics guys?

GT40XStang9 · Feb 18, 2004

Oh man.

Why does it feel like every post in this thread has been repeated eleventeen times?

The Truth about FOX FRONT BRAKES!

nito88stang

GT5.0L

New Member

chaka

sleeper89

New Member

chaka

sleeper89

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BlackFox5.0

MustangGroupie

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93 teal terror

custom89stang

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sleeper89

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Mustang5L5

That is…until I whipped out my Bissell

BlackFox5.0

chaka

chaka

DirtyD916

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DirtyD916

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DirtyD916

Active Member

Mustang5L5

That is…until I whipped out my Bissell

GT40XStang9

Thanks to Tim, I get off pretty easy.

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