GC Galant , what master cyclinder to suit rear discs.

[karl_2ltgc]

Ok ive decided im not happy with my GC's brakes. It has sigma in front and scorpian diff in rear thats locked and has the 15/17th unbooster master cylinder.

Basically the rears lock up too early and its not stopping as well as it should.

What master cyclinder should i drop into it?
Is there any bolt in type setups that are easy to get?

Also will a brake bias valve sure my problem or is it just a bandaid solution?

[shuggy]

im guessing you should find the specs of the scorp brakes and find one to match?

[karl_2ltgc]

I just want a master thats 1" or close to that suits disc rear. If it bolts on easy then even better! I will probably upgrade the front with 4 pots in the future anyway.

[Rallyant]

whats it cost to have re valved?

[Superscan811]

About $100 if you buy yourself a proportioning valve.

Cheers.

[C_Fernance]

Why not use the Scorpion proportioning valve? It looks identical to the one in my GD wagon with boosted brakes, but it would be set up for the disc brakes. All that is required to put it in is a couple of spanners.

[Superscan811]

Why not use the Scorpion proportioning valve? It looks identical to the one in my GD wagon with boosted brakes, but it would be set up for the disc brakes.

The weight and weight distribution of a vehicle is critical to the correct proportioning of brake bias.

Basically the rears lock up too early and its not stopping as well as it should.

From what I've read, it's better to lock up the fronts first BEFORE the rears. It makes the car track a bit straighter when braking hard.

Cheers.

[Rallyant]

About $100 if you buy yourself a proportioning valve.

Cheers.

Nice!
Think ill have to order me a couple of these

you seem to have found a source for everything!

[Superscan811]

you seem to have found a source for everything!

Ebay is great.

Cheers.

[karl_2ltgc]

Why not use the Scorpion proportioning valve? It looks identical to the one in my GD wagon with boosted brakes, but it would be set up for the disc brakes. All that is required to put it in is a couple of spanners.

Is that the little thing on the firewall????

Thats definately a great idea!

I'm not sure if the proportioning valve will solve my problems...

[HoonBoy]

The proportioning valve effectively limits the amount of rear brake bias, so it will do exactly what you want it to. In an ideal world you would increase the bias to the front with a staggered master cylinder setup, but that's going to be much harder.

[karl_2ltgc]

Ok sweet, well il try the scorpian thing first, if that dosnt fix things up i will just get the proportioning valve. No pedal boxes for this car.

[mbrallying]

Until just recently I had the same combo as you and I used a scorp master cylinder which is 7/8 bore. Works perfect and bolted straight in.

Only difference is that mine is boosted so I'm not sure with yours, but just thought it was worth mentioning. May be worth a look.

And you can buy them brand new.

Only thing I have changed is commodore rear calipers and its still spot on with the 7/8.

[karl_2ltgc]

Whats the deal with the commodore rear callipers?

[mbrallying]

The only reason I was using scorp calipers was for the handbrake. Which are about the worst handbrakes in the world!

Once we finally went to a hydraulic handbrake, which ditched all the scorp stuff cause the commodore calipers are heaps better for a rallycar. You can get good pads easy and cheap and also gave a tad more rear bias which is a bonus.

Next upgrade over christmas is starion rotors all round (ventilated) and commodore calipers to suit. VB-VS will fit over the fronts and VT-VZ rears are going to work on the back.

And hopefully because the piston sizes are still pretty much the same the 7/8 should still work fine....hopefully!