1994 Toyota Celica ST

ST to GT Brake Conversion

The Celica came with rear drum brakes and relatively small front discs.

Parking brakes

I sourced Celica GT rear backing plates with parking brake cables, a proportioning valve, plus four rear caliper bolts from eBay. After receiving these parts I disassembled, cleaned, lubricated, and reassembled the parking brake assemblies.

Brembo rotors

You can use new or used calipers and rotors. I decided to buy four new factory calipers and four new Brembo rotors. Here they are masked off and ready to paint.

Test fit of front rotors

The GT front rotor will bolt right up to the ST suspension. The disc just barely touches the rear brake shield and it's easy to bend it back slightly by hand.

Painted rotors

GT front brake rotors are much bigger than ST rotors. I've gone to significant expense and effort to do similar brake conversions on Datsun 510s and 240Zs over the years, so it always surprises me when someone says this conversion is not worthwhile. To me, since it's an easy bolt-on, it's irresistable.

Front rotor comparison

First step in the rear brake installation is to disconnect the parking brake cables. The connection is inside the tunnel above the exhaust system. Make sure to release the hand brake. Remove the heat shield which is held in with four bolts, then disconnect the front ends of the cables. Working space was a little bit tight but I did not need to move the exhaust system.

Parking brake cable installation

If your brake drums don't come off easily, find a couple of 8mm bolts which will thread into the holes in the drums. Run them down evenly until the drum comes off. With the drum removed, you can see the bolts that hold the spindle and backing plate onto the hub.

Brake drums and spindles removed

There are thin O-rings beneath the spindle. Be sure to keep track of them and reinstall them during reassembly. Replace them if they are brittle or damaged.

Drum brake backing plate removed

Disc backing plate installed and held temporarily by one bolt while I checked the fit of the hand brake cables

Spindle, rotor and caliper installed

You'll need the proper brake hoses for the rear discs; the drum brake hoses won't work.

Front brakes installed

The existing front brake hoses will work with the GT calipers. I replaced them as they were old and beginning to crack.

Proportioning valves

The ST vs. GT prop valve is different and so to have the front-to-rear balance that Toyota intended with the GT brakes, one should use the GT valve.

Proportioning valve pressure specs

Got this from a testing spec in a Celica manual. It seems to indicate that the difference between the various proportioning valves is pretty significant. At low pressures, balance is 50-50, but at higher pressures, rear proportion is reduced by varying amounts. So in everyday driving performance will be the same but with hard braking the difference matters. Somewhat...
1 kg/sq. cm. == 14.2 lb/sq.in. (psi)