More brake questions...

Boonie Buster · Feb 21, 2008

http://store.summitracing.com/partd...839072+4294810048+4294852109+115&autoview=sku

Will that work in my setup, I have a dana 44 and 14 bolt rear, both have disc brakes like on the front of the dana 44 (3/4 ton) will that work with my setup? It has a vaccum diagphram, what does that mean? is that dependant on my motor? or is there one without a vacuum diagphram? I am assuming i need dual diagphram for running 4 wheel disc.

Should I go with this instead?
http://store.summitracing.com/partd...839072+4294810048+4294852109+115&autoview=sku

or is that the same as the first?

:eeek: If i can solve this enigma today, there will also be a winch coming home with it on the journey from summitracing...:corn:

84Toyota4x4 · Feb 21, 2008

My uneducated opinion. The diaphragms have nothing to do with the disc/drum setup. Thats simply how much "assist" you will get. Toyotas used a single diaphragm in the early trucks, then switched to a dual later in the years and is considered to be an upgrade to go to that style for instance.

Residual valves are what dictate disc/drum application, and are built into the master cylinder typically. Theyre used (from my understanding), to keep a certain amount of fluid in the lines without letting it all flow back to the master cylinder so you dont have a large pedal travel on the first pump of the brakes to move the fluid and make the pads touch/get closer to the disc, then a short one next after they're closer/touching.

However, keep in mind you can buy external residual valves that get plumbed in line with the brake lines if you want to go that route. Then you could in theory use any drum master cylinder in a disc brake application.

Although, I have also heard of people not using the residual valves and not having any problems with rear discs at all, and just running a proportioning valve. :eeek:

~T.J.

Boonie Buster · Feb 21, 2008

ya, i was thinking of getting an adjustable proportioning valve and putting that in line of the rear brakes, but, i don;t see why a dual dia. would get you more braking power, since it takes less effort to stop, and i was reading earlier about XJ guys "upgrading" to a dual from a single in the older XJ's for more braking power with larger tires...

So, i guess i need to figure out more on the master cylinder then... but i can't imagine it being to big of a deal if i just plumb in a proportioning valve.

84Toyota4x4 · Feb 21, 2008

Nope, its not a big deal to plumb a proportioning valve in. But, that first link you have shows the master cylinder AND proportioning valve. Thats the big gold thing hanging off the side. So, since that ALSO is setup for disc/drum, you would have to replace that with an adjustable one (unless that one is).

As for the diaphragm, its just a matter of how much assist it gives you for the same amount of vacuum. So, when Toyota went to a larger bore size on the master cylinder because of the bigger rear brakes, but left the mechanical leverage the same (the pedal assembly), they needed a way to make up for the now increased hydraulic leverage (more fluid movement in the bigger bore), so they went to the dual diaphragm to give you more vacuum assist and keep pedal pressure relatively the same.

Basically, you can design a brake system anyway you want if you take the time to figure out the mechanical/hydraulic leverage ratio. Some rally/race cars dont even run boosters because they have the pedal assembly designed to overcome the hydraulic leverage easily, therefor dont need boosters.

I would try and figure out what size master cylinder you want, if you want a dual/single booster, and then go from there rather than trying to buy it all in one place. Then, once you have your generic master cylinder, just buy adjustable proportioning valves or residual valves as needed.

Heres a little info I found on some external residual valves, good info as to why you would need them. Also, it makes sense why people have decent luck without them because the master cylinder is above the horizontal line of the calipers in our trucks, so you have minimal fluid drain back. I would assume they would be more needed on the older cars with master cylinders that are below the floorboard or really low on the firewall.

These in-line pressure valves maintain a minimum brake line pressure to help eliminate excessive pedal travel to both disc and drum brake systems.
The two pound valve is used in disc brake applications where the master cylinder is mounted below the horizontal plane of the calipers and fluid drain back occurs from gravity and vibration, thereby causing excessive caliper piston retraction and a longer brake pedal stroke. The minimal two pound residual pressure prevents fluid from flowing back without causing the brakes to drag. With drum brakes, a ten pound valve is used to compensate for return spring tension in the drums. Residual Pressure Valves are made from billet aluminium and colour coded for easy identification. Ideal for drag racing, street rod and many off road applications.

~T.J.

84Toyota4x4 · Feb 21, 2008

Here, this isnt what youre doing per say, but he talks a lot about some stuff you might find helpful.

http://home.4x4wire.com/erik/4runner/brakes/#Basics

~T.J.

Boonie Buster · Feb 21, 2008

that first link should have been for a 4 disc setup... that's why i picked it...:eeek:

Not Jobless · Feb 21, 2008

I have the factory YJ booster attached to a MP Brakes vette cylinder with proportioning valve for 4-wheel discs I'll sell ya cheap.

84Toyota4x4 · Feb 21, 2008

Boonie Buster said:
that first link should have been for a 4 disc setup... that's why i picked it...:eeek:

It says in the application at the bottom for disc/drum applications? :eeek:

Notes: Fits front disc and rear drum applications.

Power Brake Booster/Master Cylinder, 7 in. Diameter, GM, Mid-Size 1964-74, Front Disk/Rear Drum, Kit

~T.J.

Boonie Buster · Feb 21, 2008

84Toyota4x4 said:
It says in the application at the bottom for disc/drum applications? :eeek:

~T.J.

oops!maybe ilinked the wrong one then..cus there was one that said for disc/disc application...

Boonie Buster · Feb 21, 2008

Jobless said:
I have the factory YJ booster attached to a MP Brakes vette cylinder with proportioning valve for 4-wheel discs I'll sell ya cheap.

PM me a price... what size is the brake booster (dia.) I am looking for as small dia. as possible, preferably 7"

Had you been using this setup on your rig? what size tires and how was the braking?:eeek:

Not Jobless · Feb 21, 2008

Boonie Buster said:
PM me a price... what size is the brake booster (dia.) I am looking for as small dia. as possible, preferably 7"

Had you been using this setup on your rig? what size tires and how was the braking?:eeek:

It's factory YJ...so whatever diameter that is? I don't have it in fornt of me right now.

I was using it in my Jeep with the 1/2 ton chevy truck front calipers and 38" swampers when it was a DD.

I had to through a adjustbale proportioningvalave in the back due to the brake lock up in the rear which was due to the big weight difference.

64FJ40 · Feb 21, 2008

Is your current booster too big? Corvette master cylinders can be had pretty cheap ($35?) and it shouldn't be much effort to adapt it to your current booster. Add an inline poportioning valve for the rear ($30) and some miscellaneous hardline and fittings and you're done for under $100 all tolled.

IMO, i'd rather build an adapter plate and custom pushrod than hack up the firewall mounting a non-stock booster (assuming your current booster works and doesn't interfere with something else).

Boonie Buster · Feb 24, 2008

64FJ40 said:
Is your current booster too big? Corvette master cylinders can be had pretty cheap ($35?) and it shouldn't be much effort to adapt it to your current booster. Add an inline poportioning valve for the rear ($30) and some miscellaneous hardline and fittings and you're done for under $100 all tolled.

IMO, i'd rather build an adapter plate and custom pushrod than hack up the firewall mounting a non-stock booster (assuming your current booster works and doesn't interfere with something else).

The original booster was rusted shut, so it needs a new one. There really isn;t a whole lot in the way of hacking up the firewall to make something fit, it just needs to be a smaller dia. to fit in the area provided. I am also pretty sure that that the stock brake booster/setup would not be efficient in any way shape or form of stopping my truck within a mile of me pressing on the brakes.:haha: So how big dia. is the corvette brake booster? that's what i need to know, I need to either just buy a custom 7" dia, (or 8") brake booster, or fins something that had that size stock with disc brakes front and rear.:eeek:

CrustyJeep · Feb 24, 2008

Is this for the S-10? Pretty sure a stock booster will be fine.

'Vette M/C's are over rated. Why? Because there are a hundred others that work just fine. You just need a diameter that matches your brakes, and a mounting that fits your booster. Big deal. I think people throw that little buzz word around because it makes them feel cool to say they have a part from a Corvette on their rig

:flipoff:

The 'Vette M/C should be 1-1/8", and that will work fine. So will 1-1/4". Mid 70's Chev. truck M/C's are in that ball park, too. Take whatever M/C you have that fits your booster to Highway Auto in Monroe and ask to see M/C's that might match with 1-1/8" or 1-1/4" diameters. They're used to it. I softened them up for you

Oh, and the original application really means jack ****; you care only about diameter and fit. Disc/disc, disc/drum, drum/drum, blah blah. The difference is in the proportioning (combo) valve. Throw it away. Use ONLY an adjustable proportioning valve in the rear circuit, and 2 pound residuals if you need them.