ST to GT brake conversion Options

[bryanf]

I finally got my brake conversion done and wanted to share some details. Brakes must be one of the Celica ST's weakest points. Or one of its best opportunities for improvement.

I got Celica GT rear backing plates with parking brake cables, a proportioning valve, plus four rear caliper bolts from ebay seller rude-day. The transaction went well and I would definitely buy from him again. The prop valve isn't essential but it's a good idea.

After receiving these parts I disassembled, cleaned, lubricated, and reassembled the parking brake assemblies.



You can use new or used calipers and rotors. I decided to buy all new ones.

I got four new Brembo rotors. Here they are masked off and ready to paint:



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 discs:



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.



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.



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.



Spindle 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. These brake hoses are interchangeable.



Car on scales. I recently installed Megan coilovers and wanted to check corner weights.



Weights with full tank of fuel and no occupants. With no adjustment of coilovers at all. Not bad.



This post has been edited by bryanf: Mar 29, 2022 - 9:53 PM

[Bitter]

The difference is because disc and drum rear brakes need different pressures but honestly you'd probably be OK reusing your ST valve. It's not a huge difference, I think drum rear apply a little less pressure out back so the rear disc brakes would apply a little less hard.