brake wars

[monaro]

the uproar in brakes just recently has been huge with performance company's realising the bigger the better but i want to know the verdict between:
harrop vs. brembo vs. ap racing
anyone with knowledge of brakes around here??

[Justin Martin]

Well, bigger doesn't exactly mean better. All a brake does is absorb heat. If no heat was generated, than a two inch brake disc would be sufficient for stopping a car. But alot of heat is generated under hard braking, and a larger disc means more heat is absorbed, hence the eight or ten inch discs seen on production cars. If the heat isn't absorbed, you experiance brake fade, which cause the brakes to become less powerfull.

Now, for simply driving around town, or even high performance street driving or autocross, your stock brake system is perfectly fine, expecially if you have ABS. If you have ABS, modifying the brake discs or calipers can confuse the ABS system, which more often than not will actually hurt braking distances, unless you know how to reprogram your car's ABS computer.

The only reason why anyone needs the 12, 13, 14 inch brake discs companies like brembo offer is for sports car racing. In a modern, 4 wheel disc brake car, even autocross or hard driving on a twisty public road probably won't generate enough brake fade to be noticeable, at least in a modern car. You need to repeatedly, lap after lap, brake hard to drop 50+ mph before you'll have brake fade, like you would in sports car racing.

The reason why companies like Porsche, Aston, Ferrari, Chevrolet, Nissan, etc are putting those huge brakes on their cars is because they are desiging their cars for racing, not because those large brakes are needed for daily driving. Their cars are capable of over 160mph, they need some serious brakes to stop a car from that speed.


Weight does come into play here also. A small, lightweight sports car won't need as big of brakes as say, a full size truck. My truck has 13 inch disc brakes on the front, partially because it weighs over 4000lbs, but mainly because it can tow over 6000lbs, which is a substantial amount of weight to try to stop.

[monaro]

thanks justin i am now much enlightened about brakes :beer:

[MattB]

same ere',

l never knew that brakes had so many different factors, thanks justin:D

[Commander]

Apart from the heat absorption, there is also a mechanical advantage to a larger diameter rotor. Think of a wheelchair, where the handles to turn the wheels are very close to the outer edge of the rim. This is because it is easier to start and stop the rotation of the wheel from the outer edge. If the same handle was near the center of the wheel, it would take far greater effort to start and stop the rotation of the wheel. The same principle applies to car brakes, so effectively, a larger rotor will require less pressure from the barke pads to slow the wheel down. Consequently, there is less wear on the components, and the vehicle can stop quicker, providing the tires maintain traction with the road. Large rotors, with slits in them for venting, are best suited for race cars that need to keep speed up until the last second before turning a corner, for example. As Justin stated, brakes for a street car should be chosen based on the vehicles characteristics and what it will be used for. Heavy dump trucks need big disks, but a Le Car or something small like that doesn't have enough weight to warrant big brakes. All big brakes would do on a car of such size would cause the wheels to lockup under normal braking, and the driver would need to be very delicate with the brake pedal, heh. At the same time, a dumptruck would probably wear out the brake pads before it even was able to come to a stop should it be equipped with insufficiently small brake rotors.

[Justin Martin]

Opps, forgot about that one TJ. -^ Yeah, there is a mechanical advantage to larger rotors, but like TJ said, once you get to a certain point larger doesn't really help you much, for most steet cars ten inches is probably about right.

[Aw614]

I don't know if this is true but I heard that a drum brake that controls the E-brake is better. Can someone clarify this. I know that the new BMW 7 series has its own drum brake just for the E-brake. I have 9.4 on my car up front and they work peferctly fine

[Commander]

I really have never heard of this, and I can't theorize on any advantages it may have either. A separate drum just for the e-brake would perhaps prevent one particular disk (from the main brakes) from wearing out prematurely, especially if you are prone to forgetting to release the e-brake before driving a few feet and "D'OH!", hehe.

[Dylan]

plenty of cars have seperate drums for the handbreak (im australian and thats what we call it) my dads car does ('85 BMW 323i) and i just got back from the melbourne motor show and there was a new holden concept there that had huge drums just for the handbreak.

[jtace]

I think drums might be prefered for the e-brake because of the pressure requirements versus a disc brake. If I'm not mistaken disk brakes need more pressure applied then the drum breaks do and most e-brakes are just cable driven and not hydralic so a drum is usefull.

[DCMattius]

I never thought of that Justin...the part about being easier to stop the wheel farther away from the axis. The only thing I can say about breaks is get some good semi-metallic pads, and make sure they are well bled. If you can lock up the wheels without much pressure, you don't need anymore stopping power. In autocrossing, the breaks don't heat up too much. I've seen Mazda Motorsports sell expensive break pads that work best in different temperature ranges. Certain pads that are great for Sebring/Daytona would be terrible on the street because they would never get hot enough. Good stock pads are great. I also think a good stock clutch is great also. I've tried some other ones with duel clutches blablabla, but the stock one lasts the longest for me. For better breaking, I would spend money on some better tires. My autocrossing tires are Kumhos and the street tires are Dunlops..both work excellent.

Matt

[racecar1]

Depends what the application is. Street use? Just better pads plus perhaps stainless steel brake lines and high quality brake fluid like Motul or at least DOT4. Then put the money into tires and other stuff. Same with Autocrossing.
But for race track use (racing or driving schools), investing in an improved overall system becomes important. I can't compare systems but know from experience you want slotted rotors, not drilled. Slotted rotors appear like having 3 or 4 slots cut into them at 45 degree angles but otherwise the rotor is smooth. This improves heat dissipation 10-20 % over a flat rotor. Drilled rotors (lots and lots of holes) may look cool and do dissipate heat better than flat, but usually result in heat cracks developing prematurely between the holes, then you throw them away :(
A system has to be balanced, ABS or not. Usually this means different front and rear rotors, a larger master cylinder, stainless steel brake lines, larger calipers and a brake proportioning valve. And the method of changing brake pads must be simple and fast too.
On track, a better brake system will get you more improvement in lap times than anything else except tires :)