High Performance Celica Brakes
A very important thing to remember about brakes is that they are simply energy converters that change motion into heat via friction. Because of Newton's second law, the Conservation of Energy, a car will not just stop, the energy of motion has to go somewhere. If the car hits a brick wall then all of that energy goes into deforming the brick wall (and the car!). But that is not what we want. We want to grab onto the wheels and slow them down, using friction. Friction causes heat, the energy for the heat is coming from the motion of the car. It is a literal transference of energy, the more heat that is made the more energy of motion will be used up. So the motion is changed into heat. The more area that is swept by the brake pads causing friction, the more efficient the braking system will be. The more heat the brakes can absorb and dissipate, the more effective the braking system will be.
There are primarily two kinds of brake mechanisms at work in automobiles today; there is disc and the drum. The older design is the drum. Drum brakes are simply two brake shoes that press against the inside of a drum. The shoes are actuated by a hydraulic wheel cylinder, which simply spreads the shoes apart, forcing them onto the drum. Many older cars had drum brakes on all corners. The newer setup is the disc. A disc brake is basically a hydraulic clamp pressing brake pads against a disc. The clamp is called a caliper, the disc is called a rotor. Disc brakes are a significant improvement on drum brakes for several reasons. They can sweep a lot more surface area in the same space under the wheel. They dissipate heat faster. They are even easier to work on than drum brakes!
All of this hydraulic system (wheel cylinders and/or calipers) is controlled by the brake master cylinder. This is simply a hydraulic pump that you control with the brake peddle. Pumping brake fluid from the reservoir to the system hydraulics, and letting it flow back.
The RA6x Celica's and MA6x Supra's have great braking systems. The earlier Celica's had disc brakes in front and drum brakes in the rear. The later Celica's and all Supra's had disc brakes on all four wheels. All had a vacuum assisted power brake master cylinder operating two circuits independently. The front wheels are on one circuit and the rear wheels are on a different circuit. The idea being a built in brake redundancy, if you had a brake failure in one circuit the other would still function.
The Celica and Supra disc brakes are great! A single piston, sliding caliper operating on a nice big rotor. 257x20mm (10.1in) diameter front rotors, and a 264x18mm (10.4in) rear, on the models so equipped. The rotors have the added benefit of being ventilated. This ventilation allows air to flow through the rotor while in use, which of course will help heat dissipation immensely. The total swept area on a 4-wheel disc Celica or Supra is 367sq-in.
The Celica rear drum brakes were very well designed, for drum brakes. They had enough size to work effectively for this car, whereas most drum brakes are undersize.
This system works great in stock form but if you really want some braking power you will have to change a couple things in the system.
The first major item to address are the early Celica drum brakes. They can function great but for a 'real' sport car you will want four wheel disc brakes. Since all Supra's had disc brakes you can swap your drum equipped rear end for a Supra's rear end with discs. This swap is almost easy for the Celica GT-S (See: How-To: Supra Rear End Swap), but the GT is supposed to be a bit tricky.
A common cause of soft peddle and soft braking are the rubber brake lines. If you really want to feel the brakes you will want to upgrade your break lines to braided stainless steel lines. These lines will not expand like rubber ones do. Stainless steel brake line kits are available from Techna-Fit.
Now to upgrade the rotors. You have three choices with the stock disc brake; OEM, slotted or crossdrilled. Which one is better is an argument for the ages. OEM is good because it has the most mass, hence heat absorbing. Slotted is good because it scrapes the pads clean and gives a good bite. Cross drilled rotors are good because they are lighter, offer good bite and breath more. You may hear of these designs allowing break gasses to escape, but modern brake pads just don't generate enough gasses to effect anything. There are also problems with each design. Cross-drilled rotors don't have as much mass as the others (so less heat absorbing). They also have the possibility of cracking. Slotted have a little less mass and have a possibility for cracking, and OEM just don't have slots or holes!
I won't tell you what to pick but I can tell you what others have chosen. All nascar vehicles run slotted rotors. Most ricers run cross drilled rotors, and people who just don't know, or know too much, run OEM. I run and prefer cross drilled, Brembo crossdrilled. I have had great results with x-drilled rotors on my 83 Celica GT-S. "Like someone threw an anchor out the back". I highly recommend the Brembo brand, KVR is also a good brand of rotors. Both are available from Cyberspace Automotive Performance.
There are many brands and styles of brake pads. The primary styles are organic, semi-metallic and metallic. Semi-metallic or metallic pads are usualy designed more for the sports car. Remember if you get all out race pads they wont work at all until they are warmed up. There are many good brands. I have heard good things about KVR carbon fibre pads, I am currently running Raybestos pads (but will get KVRs next time). Porterfield is also said to make great pads.
One often overlooked upgrade is the brake fluid. If you will really be working your brakes will need a better brake fluid. There are four common grades of brake fluid DOT3, DOT4, DOT5, DOT5.1. Most car manuals say to use DOT3 but there are advantages to the other kinds. DOT3, 4 and 5.1 are glycol-based, where DOT5 is silicone-based. Brake fluid has one simple job, to flow and not to compress. The problem is brakes get hot, and if they get hot enough, the brake fluid will actually boil. The bubbles from boiling brake fluid do not work as brake fluid, they compress. You have lost a large portion of your stopping ability if there are bubbles in the system. Glycol-based fluids are hygroscopic, that is they have a tendency to absorb water. The more water they absorb the lower the boiling point goes. So these fluids are labeled with two temperature numbers (i.e. 290F/230F), the first is the dry boiling point and the second the 'wet' boiling point. Silicone brake fluid does not absorb water. But that can lead to water pooling in the brake lines, causing corrosion. You want the highest boiling points you can get.
For the Celica/Supra brake system I would only suggest DOT3 or DOT4 brake fluid. Remember, performing a brake system flush every once in a while will allways be a good idea. I run Motul DOT4 synthetic Racing Brake Fluid 600 (593F/420F). This is probably the best fluid you would want, good luck finding it though. It has a dry boiling point of 593 degrees F!! My Brembo rotors would be nothing more than flaming-molten chunks of metal at the temperature. There are slightly better fluids but those are VERY pricey. With the Motul RBF 600 you have to keep up brake system flushes regularly because it is fairly hygroscopic.
Brake Parts/Manufacturers List
Pads and Shoes
- Repco Metal Master
- Motul RBF 600
- Castrol SRF
- Wilwood Hi-Temp 570