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Upgrade Brakes - advice please

Thanks for the info.

I have flushed my brake system a few months ago and the brakes didn't get any better.

Over the weekend, I measured my brake pedal and it has a 6:1 ratio. It's the right one for disc brakes.

The travel of the 1" master cylinder is not very much. I looked at the JMC hydraulic clutch MC location and it is really close to the brake MC so it seems that a 7" brake booster will not fit. Some people have suggested a 15/16 MC, but I am concerned about this being too little of a change.

I'd like to try a 7/8 MC. Can someone identify a 7/8 MC that will work for a disc/drum setup?

Wilwood has a 7/8 MC, but I don't know if it is a drum/drum unit with built in residual valves. If not, then this may work.
 
I purchased a 21mm MC for an 83-86 Mustang with manual disc brakes. The brake pedal should move about 1" more than it did with the 1" MC based on my calculations, and brake line pressure will go from 955 psi to 1394 psi with 125 lbs of pedal pressure. Pedal movement with the 1" MC was about 2.1" before resistance was felt. It should be about 3.1" now which is still almost 3" above the floor.

I painted the MC and filled it with DOT 5 and bench bled the it the other day so it's ready to install this weekend. DOT 5 does not damage painted surfaces...I should have used it originally when I built the car. First order of business will be to flush the old DOT 3 out of the system.

Should be pretty drastic change...
 
That's a pretty healthy change. More than the 7/8" would have given you. Be sure not to skip leg day at the gym! lol
 
"blackford" said:
...painted the MC and filled it with DOT 5...DOT 5 does not damage painted surfaces...I should have used it originally when I built the car. First order of business will be to flush the old DOT 3 out of the system...
Click to expand...

Here's another vote for DOT 5. I've run it in my '69 for 15 years and it's great. I have heard it doesn't do as well in high heat (open track) environments, but I've had no problems with spirited street use.
 
"GrabberOrange69" said:
"blackford" said:
...painted the MC and filled it with DOT 5...DOT 5 does not damage painted surfaces...I should have used it originally when I built the car. First order of business will be to flush the old DOT 3 out of the system...
Click to expand...

Here's another vote for DOT 5. I've run it in my '69 for 15 years and it's great. I have heard it doesn't do as well in high heat (open track) environments, but I've had no problems with spirited street use.
Click to expand...

I've read the opposite...it is very well suited for track use. Higher boiling point.

I've got to flush my system with an intermediate fluid since DOT 5 and DOT 3 mix like oil and water. DOT 3 is heavier so it sits on the bottom with a layer of DOT 5 on top. Never going to be able to flush DOT 3 with DOT 5 directly. I read that denatured alcohol can be used to flush it out.

Do you refresh the fluid in the system occasionally? DOT 5 does not absorb water and i've read that it should be flushed yearly or so.
 
I've flushed it once. But I live in the Mojave desert where humidity hovers close to single digits 11 months of the year.

My investigation into DOT 5 stopped 15 years ago - so maybe my info is dated. But IIRC it's compressible at a lower pressure than traditional fluids. FWIW....
 
So I finished changing my MC from a 1" bore to a 21mm or ~13/16 bore. Brakes do require less foot pressure to stop. I've had to move the brake pedal higher than I thought because of the increased travel, but its a minor issue.

More on my mind is the brake performance even after the change. Should I be able to lock up the front brakes? I want to be able to stop like my daily driver does.

I can lock up the rear brakes easier than before so I adjusted the prop valve to reduce lock up on hard braking. Am I expecting too much or do I need to turn my attention to something else that can make the brakes better? The 10+ year old RS2 pads/shoes are in the back of my mind. I have a set of semi metallics in my shed that I took off the car 10 years ago that I could try but they are 10 years old also and i'd be changing pads without turning the rotors so I might be wasting my time.

When cold, the RS2s aren't great. Once they get warmed up, they work a lot better. I resurfaced them recently and then I took them out to burnish them. I still had the old MC on the car so maybe I could not apply enough pressure to the pads to burnish them properly.

Part of my dilemma is I don't know how much I should expect from manual 4 piston KH brakes...maybe i'm expecting too much and I should not compare them to new car brakes...or maybe I need to replace my 10 year old pads and shoes and get the rotors and drums turned. Probably wouldn't be a bad idea.
 
I was still not happy with brake performance so I bought and used a brake system pressure tester. Pressure was 1700 psi front and 1100 psi rear...not a problem.

I replaced the 10 year old RS2 pads with 10 year old semi-metallics that I took off the car when I put the RS2s on...and the brakes were night and day different. Even after resurfacing the RS2 pads, they just were not working very well anymore...probably gotten hard over the years or possibly glazed and I did not remove enough material when I resurfaced them. All I know for sure is the semi-metallics have solved any lingering brake problems and the brakes work really good now...probably better than ever. The smaller MC has made my manual brakes work much like power brakes...now I can enjoy driving my car again.
 
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