alright so i took the bigger four point calipers off mt vert and stuck them on my gtu with steel braides lines and had to take the rear singles because their wider to accept vented rotors. i hooked them up bled the crap out of them. and the brake pettle is still slightly mushy and the car stoped faste with singles all the way aroud. i mean with the singles it would brake lookse the tires if i slammed on them. in the vert (rip) it would brake loose the tires if i slammed on them. its an 89 gtu and a 91 vert

the part number on the two master cylinders are the same so idk

the rotors got slightly rusted but it quickly wore off with a short drive
maybe i try new pads but if the dosent work is their a bigger master cylinder i can use i know the turbo is a littlee bigger but ive herd rumors of a full 1in cylinder that swaps in
please help thanks guys

 

I would start by bleeding everything all over again since you've driven the car air pockets that may have collected should have moved and may be easier to get it all the air out, mushy pedal means air in the lines or a leak(pulling air in the line) assuming the master cylinder/brake booster were in good working order before hand, speed bleeders can be helpful too

 

You need to also change the booster and MC since the one for ugly brakes is smaller

 

I've had to use a vacuum bleeder to completely remove all air from the 4-pots. I chased a mushy pedal for a long time.

 

same part number means same mc and booster its the turbo thats bigger and the brakes are from my vert. read desription fully please

 

IMO, none of the OEM FC masters/boosters are great with the four piston calipers.
Move up to a 1" Honda or 1 1/16" Subaru master cylinder (and their matching boosters) to get good pedal feel.

 

I know is not the same but i have turbo brakes/calipers and rotors(cross drilled and slots)with spacers on my 4 lug fc and it does stops fine with the stock brake booster master cilinder units.It did felt mushy when it was done but a quick bleed with the vacuum pump did take care of that.

 

One dumb question, when you swapped the brakes did you make sure that the bleeder screws were still at the top of the caliper and you didn't get them mixed up side to side?

Mazda was a little screwy when it came to the 5-bolt brakes and master cylinder combos on the different chassis. The GXL and convertible models got the bigger 5-bolt brakes but they were stuck with the smaller 4-bolt 7/8" master cylinder - the combo still works, but the pedal travel is a bit too long. Not sure about the combo on the GTUs models. The Turbo II models at least got the 15/16" master cylinder and with a slight larger booster. You can step up to that combo or the 929 model's 1" setup or the units that clokker suggested that will all reduce the pedal travel and firm up the feel.

 

I would love to see more info on the subie master cylinder, as Ive got one laying around. Never heard of this being done.

 

The 1 1/16" master cylinder and matching booster from a mid-90s Legacy is a direct bolt in for the FC.
I did it here.

 

Oh I see, its just for the NA's?

 

Um, no.
It works on any FC.

 

Well no I mean, is it an upgrade in comparison to the turbo MC?

 

It's a bigger mc and booster than any stock FC setup, turbo included.
And yes, in this case bigger does equal better.

 

only the S5 Turbo got the bigger master and booster, the S4 turbo is like the GXL/vert/GTUs

really that combo, the S4 master, booster, and 4 piston brakes were standard globally, and the single piston stuff seems to be unique to north america.

 

Hey clokker, what did you end up keeping on/ what did you prefer the best from your setup? That was a great write up btw on your endeavors. I commend you on all that r&d.

 

When we were building the V-8 FD I really wanted the big Subie setup but my yard had no good donors, so I pulled it off my FC. The FC ended up with a 1" Honda combo and I've been too lazy to mess with it since.
I still consider the 1 1/16" Legacy unit to be the best but the 1" mc's work almost as well.
Especially since I just street drive, where braking performance is rarely tested.

 

as important as it is, and will all the work involved swapping parts and bleeding and what not- you couldnt spring for a new subie master lol?

 

I needed a master AND the booster and no, I couldn't afford new.

 

I used a 929 booster and cylinder when I did my 4pot swap. Worked perfectly. cost very little money.

 

Mazda 1989 Mazda 929 at my yard. This the one?

 

 

There's also a 99 Legacy, and an 01 Outback. 99 Legacy the one you used Clokker? Idk which one to go for lol

 

i just did clokkers swap a couple weeks ago haven't had a chance to give it a drive so comment on the feel til the whole car is up and running again. but i have a matching master and booster came from a 97 legacy gt w/ abs