Brakes
16-Jul-2003, 09:57 AM
#1
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Brakes
OK... Jay, you asked for brakes:
What I've learned over the years is to choose the SMALLEST brakes that will effectively stop your car. Why the smallest?? Unsprung/rotational weight is the worse weight of all, and brakes are by no means light. So, that's why you take the smallest system that will do the work for you. Like drag Civics take CX and VX brakes cuz they are light and stop okay... Street cars often use GSR or ITR systems... Race cars use GSR knuckles with big brake kits...
Auto-x would most be concerned about fade... low speeds, lots of heavy braking (though low speeds), not much airflow... I know it's not 120-0 stops or anything, but its enough to boil some fluid after enough runs.
There are several factors in a brake system that make it an effective one... like how much heat will it hold/dissipate, how far is the caliper away from the center axis of the axle, how hard can the pad grab the rotor, how is your brake bias, how easy are the brakes to modulate, and finally, how good are your tires.
How far the caliper is from the center has to do with torque... the farther out you place it, the more leverage it has. This takes away from rim clearance.
How much heat it holds has to do with fade resistance... big massive brakes hold a lot of heat. Or you can hope to dissipate the heat quickly through vents and aerodynamically tested wheels.
How hard can you grab the rotor... well, that comes down to pad material and system pressure. Give properly sized flow rates for the booster/master cylinder pressure should really not be a problem... pad material, the harder it grabs, the more rotors you go through.
Brake bias will affect your handling and weight transfer. Whatever locks up first is the part of the car that will first meet the guiderail. If the rears lock, they'll wanna bring the car around in a tailspin. Fronts lock up and you'll understeer right into the wall. Modulation comes in here as well, as to how the brakes feel under your foot, and how easily can you bring them to the limit w/o locking them up.
There are two main caliper types... floating and fixed. Basically... for a club with mosly street cars, there is no sense in going any further. Our calipers have guide pins on which they slide on... there is one piston that pushes the back side of the rotor, thus sliding the caliper in towards the car and putting pressure on the other pad... by laws of physics (all other things ignored like the friction of the guidepins) the pressure will divide evenly over the two pads, even though it's just a single piston. Now, the piston inside the caliper travels and displaces volume.... the area of the piston times the distance travelled... this volume must come from somewhere... it comes from the brake pedal travel. The master cylinder is valved exactly to displace a certain volume of fluid and make a certain sized piston travel a certain distance. Changing the size of your caliper w/o changing the master cylinder is a no-no cuz now your pedal travel will be all fuct up, and the brakes will be hard to modulate... not only that, but the pressure inside the caliper will drop as well for any given amount of work done by the pedal (and by work, I mean force and distance in the traditional physics sense)... so now you have a bigger caliper, but it can't bite as hard... it's like a chick having big ****, but they are saggy
No good.... so you have to return the brake system to a balance of volume and pressure by way of changing the master cylinder. Ok, that's enough about that...
Pads are pretty well undestood I think, no?
Fluid... carries heat... transfers kinetic energy from m/c to caliper. Goes through lines... lines MAY expand a bit, if buying lines get Earl's or Goodridge. Remember that braided stainless will collect salt in winter... salt not good for car.
Boiling bluid is full of air bubbles... air bubbles do not transfer kinetic energy...in fact they like to absorb it, you push pedal, air compresses... car not stopping. Oh-oh That's called fade.
...ok gotta do something... continue later
What I've learned over the years is to choose the SMALLEST brakes that will effectively stop your car. Why the smallest?? Unsprung/rotational weight is the worse weight of all, and brakes are by no means light. So, that's why you take the smallest system that will do the work for you. Like drag Civics take CX and VX brakes cuz they are light and stop okay... Street cars often use GSR or ITR systems... Race cars use GSR knuckles with big brake kits...
Auto-x would most be concerned about fade... low speeds, lots of heavy braking (though low speeds), not much airflow... I know it's not 120-0 stops or anything, but its enough to boil some fluid after enough runs.
There are several factors in a brake system that make it an effective one... like how much heat will it hold/dissipate, how far is the caliper away from the center axis of the axle, how hard can the pad grab the rotor, how is your brake bias, how easy are the brakes to modulate, and finally, how good are your tires.
How far the caliper is from the center has to do with torque... the farther out you place it, the more leverage it has. This takes away from rim clearance.
How much heat it holds has to do with fade resistance... big massive brakes hold a lot of heat. Or you can hope to dissipate the heat quickly through vents and aerodynamically tested wheels.
How hard can you grab the rotor... well, that comes down to pad material and system pressure. Give properly sized flow rates for the booster/master cylinder pressure should really not be a problem... pad material, the harder it grabs, the more rotors you go through.
Brake bias will affect your handling and weight transfer. Whatever locks up first is the part of the car that will first meet the guiderail. If the rears lock, they'll wanna bring the car around in a tailspin. Fronts lock up and you'll understeer right into the wall. Modulation comes in here as well, as to how the brakes feel under your foot, and how easily can you bring them to the limit w/o locking them up.
There are two main caliper types... floating and fixed. Basically... for a club with mosly street cars, there is no sense in going any further. Our calipers have guide pins on which they slide on... there is one piston that pushes the back side of the rotor, thus sliding the caliper in towards the car and putting pressure on the other pad... by laws of physics (all other things ignored like the friction of the guidepins) the pressure will divide evenly over the two pads, even though it's just a single piston. Now, the piston inside the caliper travels and displaces volume.... the area of the piston times the distance travelled... this volume must come from somewhere... it comes from the brake pedal travel. The master cylinder is valved exactly to displace a certain volume of fluid and make a certain sized piston travel a certain distance. Changing the size of your caliper w/o changing the master cylinder is a no-no cuz now your pedal travel will be all fuct up, and the brakes will be hard to modulate... not only that, but the pressure inside the caliper will drop as well for any given amount of work done by the pedal (and by work, I mean force and distance in the traditional physics sense)... so now you have a bigger caliper, but it can't bite as hard... it's like a chick having big ****, but they are saggy
No good.... so you have to return the brake system to a balance of volume and pressure by way of changing the master cylinder. Ok, that's enough about that...Pads are pretty well undestood I think, no?
Fluid... carries heat... transfers kinetic energy from m/c to caliper. Goes through lines... lines MAY expand a bit, if buying lines get Earl's or Goodridge. Remember that braided stainless will collect salt in winter... salt not good for car.
Boiling bluid is full of air bubbles... air bubbles do not transfer kinetic energy...in fact they like to absorb it, you push pedal, air compresses... car not stopping. Oh-oh That's called fade.
...ok gotta do something... continue later
16-Jul-2003, 10:32 AM
#4
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Wait, but that's not all!
Proportioning valves... they distribute fluid front to back and side to side. Left and right should get even amounts, front and back should get different amounts (more front than back). If you radically alter the F/R weight distribution, it's time for an adjustable prop valve. Wilwood and Brembo make nice ones.
ABS sucks... it's more effective to modulate the pedal to the threshold braking point of the tires that it is to let a mechanical system modulate pressure for you. However, ABS does allow you to steer in the winter while braking, which 99% of the drivers out there do, even though they shouldn't. So for most ppl ABS is a good thing, for race cars, it's really not.
In tests, cars with slightly upgraded top of the line OEM systems outperform the same model big brake kit cars. Ie. Sport Compact Car had a shootout of tuner RSX-S cars... ones with a slightly upgraded stock system outperformed the big brake kits like AEM, etc.... why?? it's all about balance in the hydraulic pressure.
Bottom line... OEM brakes from a big heavy powerful car on a small light car make for a very good combination, also in terms of servicability. So GSR brakes on an EG or ITR brakes even are totally sweet
One note about higher temp capacity fluid... the seals in your calipers and m/c will either melt or crack over time under a lot of stress... you'll blow your seals if you boil your fluid too often. Avoid doing that, and try to stay under 450-500 in terms of dry boiling point of the fluid.
Now, to talk about vented, cross drilled, slotted, solid rotors... and also about drums
Most front brakes are vented, unless you got a 1986 Jetta Gl or something
Venting increases heat dissipation and increases heat capacity of the system. Cross drilling reduces frictional area, but aids in air flow over the brakes... but also creates points of strees that will allow the rotor to crack over time. But mainly, it allows gasses to escape as the pad vaporizes.... see pads get so hot, the gas from the vapourizing can actually render the brakes ineffective since the pad rides on a layer of gas instead of the rotor. This is why race cars use cross drilled brakes. On a street car, you'll spill fluid everywhere before the brakes ever really get that hot. Slotted ones are hard on the pads, and do the same thing as x-drilled, except they try to maintain the structural integrity of the pad so it won't crack. Solid rotors are seen on the rears on most rear-disk cars. They are light and do their job just fine. There are two types of e-brakes on 4 wheel disk cars, ones with a cable to the caliper, and ones with a drum brake INSIDE the rotor. The latter is ghay and was used on late 80s and early 90s chryslers... chryslers had a lot of problems with rear brake bias at the time.
Drums in the back... not that big a deal, at least your rims in the back stay dust free They look bad, no doubt, but I have yet to see someone prove that they are ineffective. Sure, they retain a lot of heat, but in reality, they don't do enough work to warrant switching them out. For racing, ya, I'd do it just to have better ventilation and cooling, since it shares the fluid with the front brakes, but on the street they do their job very well.
Ok, I'm done now... I think.
Proportioning valves... they distribute fluid front to back and side to side. Left and right should get even amounts, front and back should get different amounts (more front than back). If you radically alter the F/R weight distribution, it's time for an adjustable prop valve. Wilwood and Brembo make nice ones.
ABS sucks... it's more effective to modulate the pedal to the threshold braking point of the tires that it is to let a mechanical system modulate pressure for you. However, ABS does allow you to steer in the winter while braking, which 99% of the drivers out there do, even though they shouldn't. So for most ppl ABS is a good thing, for race cars, it's really not.
In tests, cars with slightly upgraded top of the line OEM systems outperform the same model big brake kit cars. Ie. Sport Compact Car had a shootout of tuner RSX-S cars... ones with a slightly upgraded stock system outperformed the big brake kits like AEM, etc.... why?? it's all about balance in the hydraulic pressure.
Bottom line... OEM brakes from a big heavy powerful car on a small light car make for a very good combination, also in terms of servicability. So GSR brakes on an EG or ITR brakes even are totally sweet
One note about higher temp capacity fluid... the seals in your calipers and m/c will either melt or crack over time under a lot of stress... you'll blow your seals if you boil your fluid too often. Avoid doing that, and try to stay under 450-500 in terms of dry boiling point of the fluid.
Now, to talk about vented, cross drilled, slotted, solid rotors... and also about drums
Most front brakes are vented, unless you got a 1986 Jetta Gl or something
Venting increases heat dissipation and increases heat capacity of the system. Cross drilling reduces frictional area, but aids in air flow over the brakes... but also creates points of strees that will allow the rotor to crack over time. But mainly, it allows gasses to escape as the pad vaporizes.... see pads get so hot, the gas from the vapourizing can actually render the brakes ineffective since the pad rides on a layer of gas instead of the rotor. This is why race cars use cross drilled brakes. On a street car, you'll spill fluid everywhere before the brakes ever really get that hot. Slotted ones are hard on the pads, and do the same thing as x-drilled, except they try to maintain the structural integrity of the pad so it won't crack. Solid rotors are seen on the rears on most rear-disk cars. They are light and do their job just fine. There are two types of e-brakes on 4 wheel disk cars, ones with a cable to the caliper, and ones with a drum brake INSIDE the rotor. The latter is ghay and was used on late 80s and early 90s chryslers... chryslers had a lot of problems with rear brake bias at the time. Drums in the back... not that big a deal, at least your rims in the back stay dust free
They look bad, no doubt, but I have yet to see someone prove that they are ineffective. Sure, they retain a lot of heat, but in reality, they don't do enough work to warrant switching them out. For racing, ya, I'd do it just to have better ventilation and cooling, since it shares the fluid with the front brakes, but on the street they do their job very well.Ok, I'm done now... I think.
16-Jul-2003, 10:51 AM
#6
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wow ... that is tons of info ... what about the setting of the parking brake .. should it be 1 click and it's full on and if so how would that alter the biasing of front to rear? would it cause lock up in the back???
16-Jul-2003, 11:27 AM
#8
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Aaron, that's one fookin horrific pic... take that **** down We'll get a better one next time, you'll be allowed to use that
gatherer, 1st click should contact, 2nd click should start to hold, 4th click should be full grab.
One click full grab will make your brakes really touchy, and will make the car easy to spin.
We'll get a better one next time, you'll be allowed to use that gatherer, 1st click should contact, 2nd click should start to hold, 4th click should be full grab.
One click full grab will make your brakes really touchy, and will make the car easy to spin.
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