Hydro-Max Brake Assist *pics added* (long read)

[spicergear]

Jake, I found a very good detailed pdf format of the Hydro-Max from, I think, Bosch. I would not run anything else after mine as it wasn't that way from factory. I would find one specifically set up like that or, which may happen, run another pump for PS like what seemed to be pretty standard on the medium duty trucks.

I simplified the braking circuit by 'commonizing' the lines. Basically brought both lines from the master cylinder down to the frame rail then brought them into a 'T' fitting. I brought them down in 1/4" line to a 1/4" 'T' fitting with a 5/16" adapter on the outlet. I even bored out the fitting a couple of drill sizes to propagate flow. I then ran a 5/16 line from there back to the 'T' fitting where the original brake line tees into the main brakes for the truck. There is no split circuit anymore. The split circuit would not work with this set up as its way uneven having 50% more needed for the rear than front. The front would make it's line pressure and apply the brakes firmly while the rear was still low pressure having to feed twice the amount of wheel cylinders. I know this as fact as I originally tried a hydroboost unit and had the brakes split.

Having the circuits commonized into one larger outlet line made this set up work as good as it possibly can. It WILL deliver all the braking power the truck needs, and obviously more by the GVW rating, and by running back into the single line it doesn't get into any proportioning whoa's or other components to complicate the system.

Parts I ended up using for this:
1) New Saginaw PS pump for '93 1 ton Chevy with Medium Duty pump's spring, pressure cartridge, and outlet fitting-
1) Ebay'ed PS pump mounts for Big Block Chevy modified to fit my CAT-
1) Ebay'ed two groove PS pump pulley-
1) Used Medium Duty high pressure line w/ new end swaged on for different formed hard line and fitting-
1) Used Hydro-Max booster and 50.80mm MC from 1997 S1700 International-
1) Hanging pedal assembly from same International, only used brake pedal-
1) 2' section of new 1/2" Gas and Oil hose for return line-
2) Sections of 3/8" PS hose used for returns from pictured fitting to pump's reservoir-
2) 3' pieces of 1/4" brake line-
1) 1/4" brass brake 'T'-
1) 5' piece os 5/16 brake line-
1) 5/16" adapter fitting-

 

[Barrman]

Tom,
Colton saw "Back to the future" for the first time last weekend. Being only 9, he sometimes has difficulty telling fact from fiction. Last night, I was messing with the Hyrdoboost I have and plan to put on the M715. I was looking at it and telling him how small it looks and really is compared to what you did. After I told him all about what you did to your Duece. ( Remember that the only time he has seen your Duece was when you were still setting up the crane.) Colton has helped me strip all the air lines and air stuff off two different cabs in the last month, so he has an idea of what all is involved with the air system. He got a serious look on his face and said "Tom could build a Flux Capacitor if he could get the Plutonium Dad, so why shouldn't he be able to make one of these fit a Duece." I just told him that you probably could.

 

[spicergear]

Here's two better pics of the Hydro-Max brake system in the engine bay.

 

[hot rod deuce]

holly crap I have one of those that I forgot I had. I think this is the only way to fly. Too bad you did it, now I gottaa come up with some thing else......

 

[Unforgiven]

Try and get the pump or if they're both Saginaw pumps, pull the outlet fitting, pressure valve and spring all out of the original H-Max pump. I found that pump to have more pressure and flow then a 3/4 or 1 ton pump. *most* of the ones I had found ran seperated systems for brake and steering, but some were in line, like normal, like you're planning on doing. I think you'll be REALLY pleased with the results- I sure am.

The system I got was off of a '97 S1700 International so it's a fairly new system. Another reason I went for this set up is that it's relatively CURRENT technology, very simple with three main components (pump, booster, MC...2" bore btw), have full brake pressure immediately after engine starts, and is rated 20,000 lbs GVW over what the deuce is on-road max rated. Sorta like using a Grizzly .50 for rabbit hunting.

This seems like the simplest, safest, and more effective way to upgrade these brakes. Plus, this guy says they can be found with an integrated power steering pump. You could do two upgrades at the same time if you wanted, brakes & power steering.

With big tires &/or differential lockers it's a no brainer. This is the way to upgrade the brakes.

 

[Jake0147]

They don't have an integrated steering pump, they require the addition of a pump, which of course then could be used for whatever you wish within it's capacity. The hydraulically powered brake booster does contain a "backup" motor that is used to make that one last stop if the engine stalls, but it's weak at best, and only supplies the brakes, nothing else on the pump circuit.
I'd consider this if I could figure out how to mount it under the truck where nobody'd see it, still using the original pedal and without removing the original master, which would have to be there to support the PTO shifter...

I keep a fleet of trucks on the road that use this braking system (or extremely similar variants of it), it is a rock solid and trouble free system, that (IMHO) is conservatively rated as to it's performance. They work well.

 

[Unforgiven]

Yeah, I was reading about the power steering. Apparently the first HydroMax's did both. And the vehicles that had them didn't have any brakes when the steering was at full deflection (crawling down a hill into a tight corner). All the pressure was going to the steering, leaving little for the brakes. So now all the HydroMax's are independent of the power steering. The only thing I don't understand is why the Spicergear guy who did the conversion didn't run 3 wheels on one circuit & 3 wheels on the 2nd circuit. I guess he had is reasons.

Still, It's good to have real-world feedback from somebody with experience. And I'm amazed how small the booster/master cylinder are for such heavy duty applications. I still own many cars with those big old vacuum boosters. They take up half the engine compartment. Just a pump & master cylinder/booster combo is all you need(with new pedal assembly). It seems like a relatively easy conversion that would bring the brakes closer to modern standards.

P.S. I finally got an A2. Not having a parking brake at a gas pump sucks! I think the pinion parking brake might be worth the $$ just to be able to idle at a pump safely.

 

[Jake0147]

three and three wouldn't work, but most of them have the same bore in the front and rear chamber (equal pressure at all circuits) so a front/rear split would work, or even a front/front rear and rear rear split would work. Or "commonizing" the lines gives all the benefits except for the split circuits, really not a downgrade, just not an upgrade in that department.
They still do (or did up till '07) use a common pump for steering and brakes. You can overload the system in a parking lot if you try, but it's an operator failure. (Second only in "false flunks" at a DMV check to electric trailer brakes that fail to lock up under a fully loaded wagon). If you're against the steering lock and still PULLING on the wheel, you'll exceed the available fluid power if the engine is idling. Keep the wheel where it is at full lock, but STOP PULLING ON IT and there is no performance deficit for either system.

You've lost me with the pinion brake for the gas pump... Does the driveshaft brake on the transfer case not work?

 

[phil2968]

So in essence, you have boosted the stock deuce brake wheel cylinders to 1800 psi but still have a single circuit brake system. I know it doesn't happen often, but what happens if a wheel cylinder lets go? I would like to upgrade my brakes but I want dual circuit for redundancy. What would be wrong with a 3 way split with one middle wheel cylinder on the opposite from the front and rear? If you lost a circuit you would still have 3 wheels to stop with. If the MC to WC dia. ratio is close it should work?

Ok, flame away.

 

[Unforgiven]

Yeah, I just bought the truck. I need to crawl under it & rip off the driveline to see why the parking brake isn't working. I had to kill the engine at the pumps then put it in gear. That kind of scared me because I wasn't too confident in the status of the batteries to restart the truck. It's amazing how just a tiny, tiny grade makes that truck start rolling. Other cars I've had would have been fine in neutral without moving. No way with this truck. What looked like absolutely flat gas stations made it roll.

Could you elaborate why a 3 tire brake system wouldn't work? It seems each circuit could be divided to push identical volumes of fluid, with the addition of one hard line to one of the tires & plugging the 4th outlet on the other line.

 

[Jake0147]

A single way "conversion" like is described in the original post does not gain the redundancy of a dual circuit, even though there are two outlets.

A dual circuit for redundancy IMHO would be worth while if you are choosing to upgrade the brake system anyhow.

As for splitting the brakes on one axle, do you really want the braking on one side and not the other? Aside from the obvious that should you ever need the redundancy, two thirds of your braking will be on one side of the truck, meaning it'll be steering it's self, and if you're lucky you can keep up with it. Then, assuming you can keep up with it, and being a driven axle, you need to consider the consequences of what's being sent back "upstream", and in a panic event (which is when components typically fail) the impending lockup of the one tire means you've got four tires at road speed, two tires not moving (sliding), and two more tires at double the road speed. you're going to be lucky if you have a quick differential or axle failure, because you have absolutely no control when the tires are hopping right off of the ground.

As far as mismatched numbers of wheel cylinders on each circuit, there is no discrepancy in the volume of fluid delivered versus required to any circuit (within some reasonable sizing limits, we're not talking about a Kia master cylinder here), a dual outlet master cylinder is self-compensating design. With a constant bore for the front and rear sections of the cylinder, It mechanically delivers a variable volume to each circuit as required to develop equal pressure in each circuit. at all times. The volume is needed to make the pressure, but the pressure is what stops the truck.

 

[Unforgiven]

The way I figure it, it would be better to be sliding sideways/steering sideways to a stop rather than ramming full speed into a Hyundai at a stoplight b/c of no brakes at all. Under normal driving, there would be no sideways pull because all the wheel cylinders would be expanding equally. Heck, do a Rockford J turn in the thing as long as it stops.

 

[Csm Davis]

ok will someone please tell me why you can't split the front off the small end and run the rear four off the big end with maybe a adjustable proportion valve

 

[mudguppy]

you can. the folks on here are believing that applying the same amount of pressure to the front as the rear will lock up the front. what they are forgetting is that the front should require more pressure than the rear since the front generally does more braking than the rear (except when fully loaded).

the single circuit system applies equal pressure all the way around, which is why the rears lock before the front. rather, if you take a dual chamber MC w/ a built-in bias (say, 60/40) and send the smaller to the front, i believe the braking proportion would be pretty dam close to spot on even with twice the volume of rear cylinders as the front. and if you use it on a bobber w/ equal wheel cylinders, i'd send 60 to the front and 40 to the rear.

 

[Unforgiven]

if you take a dual chamber MC w/ a built-in bias (say, 60/40) and send the smaller to the front, i believe the braking proportion would be pretty dam close to spot on even with twice the volume of rear cylinders as the front. and if you use it on a bobber w/ equal wheel cylinders, i'd send 60 to the front and 40 to the rear.

To replicate the current one-circuit brakes, you would have to have exactly a 66.66 rear to 33.33 front split. The 60/40 would probably still need proportioning a bit. Usually the 60/40 MC's are for front disc brakes. From what I understand, drums need to be closer in proportion.

I've been surfing trying to find just this type of Hydromax MC that you suggest with the 60/40. Probably the MC from a dual axle motor home/garbage truck/single load cement truck/or similar dual axle rear would work.

All I was suggesting with the 3 tire circuit was a "poor man's" easy way to have 2 circuits & push the same volume everywhere, therefore maintaining the exact same braking characteristics & exact same volume/pedal push as stock. Most of the readily available MC's in junk yards/ebay etc. are for 4 tire vehicles. To make this work, at least mimmick the stock system, would be to split it 3x3 because of the restrictions of the commonly found MC's. Also consider that a 60/40 split would have 66% symmetrical braking if the fronts failed. It would have only 33% symmetrical braking if the rears failed. It would have 50% asymmetrical braking either way with the goofy 3x3 way. But it would work. Preferably, a better MC choice as you suggest giving a very slight forward bias would be ideal.

Maybe if I'm good, Santa will leave a 66/33 master cylinder under the tree.

 

[mudguppy]

To replicate the current one-circuit brakes, you would have to have exactly a 66.66 rear to 33.33 front split. ...

in effect, i you are correct on your proportioning, but i'm not sold that it has to be that close. but i say that as my own professional opinion without ever having actually tried it... so it means nothing.​

the reason i believe a 60/40 split would be better is because i want more pressure to go to the front first - this is how a braking system should be because the fronts share more of the braking burden than the rears. just looking at the [archaic] single ciruit system, each wheel sees the same pressure regardless of position.​

the discussion needs to move from 'volume' to 'pressure.'​

the problem lies in braking pressure. the relationship between traction and pressure directly determine braking effort. and since traction is determined by weight + contact patch, it is not incorrect to corelate weight and braking pressure (with 'wieght' being the amount of shared truck weight shift + load). therefore, the more 'weight' that a single wheel sees then the more braking pressure this wheel should recieve in order to proportionally contribute to the overall braking effort.​

but in a single circuit system, this is simple 'path-of-least-resistance'. so if each wheel receives the same amount of pressure, the wheel w/ the least amount of 'weight' is going to lock/slip first and the wheel with the most weight is going to lock last. so when you divide it up, the wheels that need to contribute the most to the total braking effort are actually seeing the least amount of effective braking pressure that they should see in order to properly contribute.​

therefore, a properly designed [modern] braking system will provide more braking pressure to the wheels that have the most ability to provide braking effort.​

my conclusion: if i had a 6 wheeled deuce, i would split the system 40/60 (f/r): even though, by 'volume', the 60 is a bit short in the rear, you have twice the surface area pressure because you have twice the braking components. again, brakes work by friction, so pressure = friction = braking.​

secondly, in a bob'er, i believe no less than 60/40 (f/r) is proper. and in all actuallity, because the bob'er is so nose-heavy, you'd be much better off with a 67/33 split f/r because i'd bet 5 bucks that the rear will still lock up way earlier than the fronts. however, i'm going to stick with a 60/40 split and make up the last bit of rear over-braking by using a smaller rotor in the back when i do the disc brake swap and use a proportioning valve to fine-tune it.​

again, this is all just my .​

 

[booger]

Disc brakes?

clue me in

 

[Jake0147]

You guys are over thinking this...

There is no "proportioning" in this. None needed, none wanted. Equal pressure to all wheels gives "factory" proportioning. That's what you have now, that's what you want. A split master with equal bores front and rear inherently does this. Pressure in the front circuit will always equal the pressure in the rear circuit, even though the volumes are different. Until a failure, then you will have the pedal drop half way, and the mechanical stops will take over and allow the remaining undamaged brake circuit to function normally.

As far as a modern system...
Hydromaxx is a modern system. In OEM as produced trim on modern equipment, it delivers equal pressure to equal brake apparatus on each wheel, just as it should. This isn't a Ford Taurus, all the brakes have to pull their weight. The 70/30 thing that you hear about pretty much stops when you get beyond compact and a few mid sized sedans.
Everything you need for this system is done. All brakes of the same. No metering valve is used. All brakes require the same pressure to operate correctly. No proportioning valve is used. The differential valve if you choose to use it is contained within the master cylinder it's self. There are no other valves to add. If you're doing a disk/drum conversion, if you're adding bigger drum brakes to one axle but not the rest... Then yes you will need some external metering and proportioning, but for stock brakes, it's just a line to the chosen axle.

The way I figure it, it would be better to be sliding sideways/steering sideways to a stop rather than ramming full speed into a Hyundai at a stoplight b/c of no brakes at all. Under normal driving, there would be no sideways pull because all the wheel cylinders would be expanding equally. Heck, do a Rockford J turn in the thing as long as it stops.

This is my poijnt. If you're going to do this, it'd be best not to have a failure of course, but if you do...
I would rather come to a complete stop in a straight line with no squeeling, skidding, or other unnecessary drama. That's what modern brake systems deliver, I just can't see why you would go to the extra effort to bypass that feature.

 

[tm america]

nice job its a great mod since hydro boost has the highest brake pressure you can get .keep an eye on that hydro boost unit seems like they all start to leak i put hydro boost on my 1950 ford f6 4x4 i had worked out great only thing i could fit under the cab in the stock location i think you could probably have fit the hydroboost unit where the stock master cylinder was and you would have saved a backache

 

[tm america]

the 70/ 30 still applys not to having to run a proportioning valve or any of that but how much stopping power you have from things dues to the weight transfer during braking .unless you are heavily loaded in the back the rear end is trying to lift under braking and the front is getting planted this is why they run discs in the front and drums on the back on most cars and trucks even when you get into medium and light heavy duty trucks they still have discs in the front and drums in the back .semis and heavy truck have drums all the way around since they figure it will be loaded most of the time and the rears will have enough traction to run the same on all wheels