4 wheel manual disc brakes
 

Has anybody done this upgrade with 3/4 ton axles? I know it is done all of the time with power brakes but I'm looking for brakes without the engine running. I know the master cylinder has to be smaller than a 1" bore but I've been told that I can't get enough volume for the big single piston calipers and I like the reliability of single pistons:m6:. Any info or vendors would be appreciated.:m6:

Re: 4 wheel manual disc brakes
 

why brakes without the engine running?

Re: 4 wheel manual disc brakes
 

If I'm coming down the side of a Mountain and the engine floods out or dies for whatever reason, I'd still like to have brakes.

Re: 4 wheel manual disc brakes
 

So nobody has done this?

Re: 4 wheel manual disc brakes
 

Ask the guy on Pro-touring.com. They have lots of manual 4-wheel discs brakes. Many times running dual, triple, or even quadruple master cylinders. They are definitely the guys to talk to.

Re: 4 wheel manual disc brakes
 

I did this mod to my 86 K10, but still have the power booster.

I'm confused about why the volume would change, or should I say I believe it will not change. You still have the same volume of fluid being displaced weather you have the booster or no booster. I used stock front K20 calipers. I think the Cadillac ones with the ratcheting e brake pistons use less fluid. They appear smaller anyway. The original Master cylinder seems to have enough volume to make it work.

Mine works fine, I just used a cheap adjustable prop valve to get the bias correct so I don't slide the rear tires. Haven't used it on the trail, just cruised around the block so far.

Re: 4 wheel manual disc brakes
 

Not exactly the same application but my experience. 59 truck with 74 K10 axles, disc/drum and 74 stock MC and proportioning valve. I ran them as manual for 15 years. Builds up leg strength, especially on long down hill runs, but does stop, I could lock the tires up. This time I added a booster and can't wait to see the difference. I think a lot would have to do with the leverage from the pedal and push rod arm lengths.

Re: 4 wheel manual disc brakes
 

:agree::agree:

Re: 4 wheel manual disc brakes
 

Biggest thing about changing the leverage on the pedal is the throw. Moving the actuator arm up 1" on my truck was enough to make the pedal hit the firewall well before bottoming out. There just isn't much room to get more power there.

Something to keep in mind is that vacuum boosters will still work for a period of time after the engine shuts off, and Hydro boosters have a accumulator for this very purpose.

If I was really concerned about loosing the use of power brakes, I'd consider running vacuum booster, in conjunction with a electric vacuum pump as a backup. Just a thought...

Re: 4 wheel manual disc brakes
 

Thanks for all of the input. I talked to a guy I know that builds race cars and he suggested dual master cylinders and a balance bar. Wilwood and Tilton both make them. That seems to make a lot of sense to me. I would have 2 completely separate systems, 1 for the front and 1 for the back. Pedal ratio should be about 7 to 1. The balance bar lets me set up brake bias. 400PSI is enough for drum brakes but it takes about 1000PSI for discs. From what I understand, and please correct me if I'm wrong, @ 7 to 1, I would need 142lbs of pressure on the pedal to get 1000PSI @ the MC. Smaller brake lines and a smaller MC bore should also increase the pressure, Right? I'm thinking about 3/16" hard lines and a 7/8" bore MCs. Factory PDB MCs are 1-1/8" bore. Do you think I've lost my mind yet?

Re: 4 wheel manual disc brakes
 

I'm not sure on the pressure but I do have a question, what formula's did you use to come up with the numbers? I'm always looking for formulas to make things easier.

Re: 4 wheel manual disc brakes
 

Here's some links to a few of the places that I got that info
http://www.mpbrakes.com/uploads/docu...alratiopdf.pdf
http://www.mpbrakes.com/technical-su...-cylinders.cfm
http://www.mpbrakes.com/technical-su...isc-brakes.cfm
http://wilwood.com/TechTip/TechFaqs.aspx
http://www.deanoshiro.com/brakes/brakearticle.html

Re: 4 wheel manual disc brakes
 

Well, great work! You have helped me to improve my knowledge about this field. Thank you so much for sharing.

Re: 4 wheel manual disc brakes
 

The size of the hard line has nothing to do with pressure. The size of the MC determines pressure and volume. After it leaves the MC, a 3/16 line or a 2" line would still move the same amount of fluid at the same PSI exerted by the MC... this is a common debate on the Pro-Touring site...

This is not to be confused with a fuel system that needs a larger line to move more fluid