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Brake booster & Master Cylinder Recomendations

Rugby_7

Rugby_7

1/2 ton status
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I have a '75 blazer I'm putting together. 8 lug dana 44 up front 14 bolt with disc brake swap out back. New SS brake lines from inline tube with their rear disc brake prop valve. I'm at the point where I'm putting the dash and firewall stuff on. The booster from my parts blazer is junk so need some recommendations for parts. I've heard that a 3/4 ton master is an upgrade for a k5. I also heard that the lines are switched for front and rear. Is there anything that would be better than a booster and master cylinder from a 1975 k20? Rather not get into hydro boost at this time.
 
I have done two 3/4 ton conversions (both with drums), and neither time did I upgrade the 1/2 ton master cylinder. The pedal travels further with the smaller M/C, but that isn't a bad thing in my case (1/2 ton hydroboost rigs are fairly sensitive on the brake pedal).

Using the larger master isn't a bad thing, but it's not a firm requirement, either.
 
campfire said:
I have done two 3/4 ton conversions (both with drums), and neither time did I upgrade the 1/2 ton master cylinder. The pedal travels further with the smaller M/C, but that isn't a bad thing in my case (1/2 ton hydroboost rigs are fairly sensitive on the brake pedal).

Using the larger master isn't a bad thing, but it's not a firm requirement, either.
Click to expand...

I figured since I need to get new parts might as well see if there is a better replacement.
 
I bought a 3/4 ton setup with a plastic reservoir, haven't used it yet.
 
skunked said:
I bought a 3/4 ton setup with a plastic reservoir, haven't used it yet.
Click to expand...

Like from a NBS truck? When I did rear disc semi float 14 bolt on my 1995 2dr yukon I used a NBS Master on it and it improved brake feel dramatically.

Something like this:
master.jpg
 
Rugby_7 said:
Like from a NBS truck? When I did rear disc semi float 14 bolt on my 1995 2dr yukon I used a NBS Master on it and it improved brake feel dramatically.

Something like this:
View attachment 220884
Click to expand...

it was a 90's unit IIRC, there was a thread on here that talked about Master Cylinders that I followed

IMG_2569sm.jpg
 
from mine and at least one others experiences, the cast iron reservoirs on masters are inferior to plastic. generally counterintuitive, however in our cases the cast iron rusted at the seal surface for the cap, and they ended up leaking. probably somewhat uncommon, my truck sits forever, but i'm definitely going with plastic next time.

not sure what any of the different brake options specified in the 80's, but there might be some that were still cast. 1/2 was plastic.
 
dyeager535 said:
from mine and at least one others experiences, the cast iron reservoirs on masters are inferior to plastic. generally counterintuitive, however in our cases the cast iron rusted at the seal surface for the cap, and they ended up leaking. probably somewhat uncommon, my truck sits forever, but i'm definitely going with plastic next time.

not sure what any of the different brake options specified in the 80's, but there might be some that were still cast. 1/2 was plastic.
Click to expand...

I like the nostalgic look of the cast MC but I would rather have the better all around product.
 
Rugby_7 said:
Awesome! Thank you for getting me that part number. This one is suppose to provide more stopping power?
Click to expand...

My research here on ck5 led me to buy this with one tons and disc brakes on all four corners. My truck stopped fine with the stock MS, my issue was the damn thing always leaked and stripped the paint off everything below it.
 
Last edited:
Rugby_7 said:
Awesome! Thank you for getting me that part number. This one is suppose to provide more stopping power?
Click to expand...

"Stopping power" is a misnomer. That is controlled by the size of your pads and the total amount of leverage when you add up all the linkages. What the larger M/C does is it has a larger piston allowing your pedal stroke to move a larger volume of hydraulic fluid. This does not change the mechanical advantage anywhere in the circuit, it just changes the length of the stroke required to activate the brakes. You will find that your pedal moves less distance before the wheels lock up. It's more sensitive. It's neither good nor bad, it's just different. But it's not the M/C that gives you more braking power (unless you're bottoming out the small one). The larger hub diameter & slave cylinder diameter is what gives you more "stopping power."
 
I have 3/4 ton rotors, calipers, and pads front/back. I wish I could test what stock would be like, but that wouldn't be able to happen for months. Trying to find the best combo to purchase once
 
So probably a better question would be if this combo would move the fluid needed for these larger calipers?
 
Rugby_7 said:
So probably a better question would be if this combo would move the fluid needed for these larger calipers?
Click to expand...

If I understand correctly, you'd essentially be running a stock 3/4-ton disc/disc system with a 3/4-ton master. Should be right on the money if the proportioning valve is correctly set up for discs. Personally I'd get an adjustable proportioning valve, but that's because I like fiddling with things. :haha:
 
campfire said:
If I understand correctly, you'd essentially be running a stock 3/4-ton disc/disc system with a 3/4-ton master. Should be right on the money if the proportioning valve is correctly set up for discs. Personally I'd get an adjustable proportioning valve, but that's because I like fiddling with things. :haha:
Click to expand...
Summing that all up just made it click for me. I think it will be perfect!
I had an adjustable one on that Yukon I had, I was always changing it.
 
campfire said:
"Stopping power" is a misnomer. That is controlled by the size of your pads and the total amount of leverage when you add up all the linkages. What the larger M/C does is it has a larger piston allowing your pedal stroke to move a larger volume of hydraulic fluid. This does not change the mechanical advantage anywhere in the circuit, it just changes the length of the stroke required to activate the brakes. You will find that your pedal moves less distance before the wheels lock up. It's more sensitive. It's neither good nor bad, it's just different. But it's not the M/C that gives you more braking power (unless you're bottoming out the small one). The larger hub diameter & slave cylinder diameter is what gives you more "stopping power."
Click to expand...

That is part of the story, hydraulics work by the pressure versus area in the system. Just to keep it simple I'll ignore the booster and just some nice round numbers for the sake of illustration. Say the piston in the mc is 1 square inch and you push with 100 lbs of pressure the whole system will have 100 lbs per sq. in. or 100 psi. So if the caliper piston has, say, 4 sq inches of area it will have 400 lbs of pressure against the pads but for each for an inch the piston moves in the mc the caliper piston will only move 1/4 inch. If you go to a 2 sq in piston in the mc you will now only have 50 psi in whole system and you will have 200 lbs of pressure against the pads with the same size caliper piston but it will now move 1/2 inch.
If you upgrade brakes (axle swap) you're going to have to keep up with the fluid volume required to adequately apply the brakes without an excessive amount of pedal travel. When you increase the size of the bore in the master cylinder to increase the volume of fluid you're moving you need to upgrade the booster at the same time in order to maintain the pressure that the pistons are applying at the wheel ends of the axles.

Gus
 
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