Power master brakes
- Thread starter butch2000
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This has been discussed at length. I prefer vacuum, but you need to make sure you have enough vacuum and a good checkball to keep it in the booster. Hydroboost stops better but is more complex and leaky. Powermaster rebuild is the best but expensive and you still never know when it will fail again. The lifetime warranty doesn't cover damage you do when they do fail.
IMO, powermaster for strip use primarily with extra regular fluid changes, vacuum for a car driven a lot on the street for reliability (with a good, maybe even two, checkballs). Hydroboost is a blend of both other system's attributes. If you need to launch really hard, get a transbrake regardless of what brakes you run. I accept my low boost launch b/c I use vacuum brakes but it still 1.6x 60's, so I don't care.
IMO, powermaster for strip use primarily with extra regular fluid changes, vacuum for a car driven a lot on the street for reliability (with a good, maybe even two, checkballs). Hydroboost is a blend of both other system's attributes. If you need to launch really hard, get a transbrake regardless of what brakes you run. I accept my low boost launch b/c I use vacuum brakes but it still 1.6x 60's, so I don't care.
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Dave I do agree hydroboost is complex when doing a change-over, but stopping power is the mechanical function of many items in the brake system including tires, and using a different manner of powered assist does not give better stopping.
Reliability of the different assist systems is another matter!
All I know is, the hydroboost system on my Ford Excursion will stop that 8,000# monster a lot better than most other vehicles I've driven over the years.
I know a lot of folks wont agree with me, but I'm a firm believer that vacuum brakes have no place on a turbo charged application. The Factories saw the need to put hydroboost systems on all their turbo diesel powered pickups and light duty trucks (Ford and GM). I'm not familiar enough with Dodge to even know what kind of brakes their turbo diesel pickups use.
I know a lot of folks wont agree with me, but I'm a firm believer that vacuum brakes have no place on a turbo charged application. The Factories saw the need to put hydroboost systems on all their turbo diesel powered pickups and light duty trucks (Ford and GM). I'm not familiar enough with Dodge to even know what kind of brakes their turbo diesel pickups use.
Ya, I forgot about the no throttle body thing. You'd think I would remember that since I'm driving one. 
But I still stand by my belief that forced induction cars just should not be running vacuum brakes, without some kind of additional help that is.
But I still stand by my belief that forced induction cars just should not be running vacuum brakes, without some kind of additional help that is.
I'll echo that the HB systems are among the best. I saw a comparison once that suggested the PM was about the same as far as pressure delivered to the calipers..... but most will agree the PM system is unreliable. I took a perfectly good PM system off my '87 GN and converted it to HB using a junkyard HB system off a Astro Van...... took a little work, but I am totally satisfied....and it has been on my car 2 years or so. I recently launched off the FB @ 14 psi per the datalog and the car never wanted to push through the lights.
I think the vacuum systems are extremely reliable, and work well in our cars..... but only provide about 1/2 the pressure to the calipers that a working HB setup can put on it. Make no mistake, you will never get the braking performance from vacuum that you can get with HB.
I think the vacuum systems are extremely reliable, and work well in our cars..... but only provide about 1/2 the pressure to the calipers that a working HB setup can put on it. Make no mistake, you will never get the braking performance from vacuum that you can get with HB.
You need to compare apples-to-apples. A vacuum system on stock brakes is a downgrade - period. It makes between 1000 psi and 1300 psi from what I have read..... with dual diaphram vacuum boosters making more than the more common single diaphram. HB systems make between 2000 and 3000 psi. If you want to increase braking performance with a vacuum system (lower pressure), you need to increase the swept area (pad surface area) as well as larger diameter...... it has to do with how far away from the centerline of the axle.
With that said, you can put huge brakes on a vacuum boosted car and get the excellent stopping power. (you will also be out of cubic $$ too)
Most people here are comparing vacuum brake conversions on stock braking systems (rotor size and pad size)..... vs. hydroboost brake conversions on stock braking systems (rotor size and pad size).
Once you have the ability to lock-up the wheel, you can't exceed the potential of that performance.
Where the big baer systems begin to leave stock based brakes in the dust is the much larger calipers/pistons/pad area and diameters...... all this means the brakes are able to shed heat faster and will perform better under continuous use than the stock components were designed to do. The big baer systems are not as likely to experience brake fade when used repeatedly or "glaze" the pads over.
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I stand by my statement that the method or assist in not relevant when comparing braking performance on a specific vehicle.
In the 70's/80's I had a fleet of trucks running around Arizona, some with vacuum, some of the same model with HB. It was NOT possible to tell any difference in stopping power or distance between the 2, either loaded or unloaded.
One BIG difference I did notice unfortunately, was the high maintaince of the HB systems, and never remember replacing a vacuum booster?
For the ultimate in reliability my race car has manual brakes.
I also challenge and dis-agree with your statement " A vacuum system on stock brakes is a downgrade - period."
My actual experience gives me the opposite results?
In the 1990's, a local GN owner was very unhappy with is braking performance and reliability of his PM. I replaced pads, shoes, calipers, but no improvement.
We tested braking performance by locking up the brakes at 30 MPH and measuring stopping distance. The same day I installed a vac booster and ran the same tests again. The exact shorter distance with the vac system, I cannot recall, but it was in the 20-30% range.
If you have different test data, I would sure like to see it.
In the 70's/80's I had a fleet of trucks running around Arizona, some with vacuum, some of the same model with HB. It was NOT possible to tell any difference in stopping power or distance between the 2, either loaded or unloaded.
One BIG difference I did notice unfortunately, was the high maintaince of the HB systems, and never remember replacing a vacuum booster?
For the ultimate in reliability my race car has manual brakes.
I also challenge and dis-agree with your statement " A vacuum system on stock brakes is a downgrade - period."
My actual experience gives me the opposite results?
In the 1990's, a local GN owner was very unhappy with is braking performance and reliability of his PM. I replaced pads, shoes, calipers, but no improvement.
We tested braking performance by locking up the brakes at 30 MPH and measuring stopping distance. The same day I installed a vac booster and ran the same tests again. The exact shorter distance with the vac system, I cannot recall, but it was in the 20-30% range.
If you have different test data, I would sure like to see it.
I can't believe you tried making that comparison!!! I'm intimately familiar with Scot's car. Trust me , you can't make that stretch! His car's fenominal braking abilities have nothing to do with the fact he's running Vacuum, and has everything to do with the mods at each corner!!!
This isn't what he is saying. He's saying that the car stops great and doubts it would stop any better with a different kind of assist. I agree.
Hydratech
I went from a powermaster to the hydratech unit and couldn't be happier. The unit itself is smaller than the power master. With this kit, although pricey is pretty simple.
.......snip ......
I also challenge and dis-agree with your statement " A vacuum system on stock brakes is a downgrade - period."
My actual experience gives me the opposite results?
How many threads have you seen on here where people with vacuum systems are having trouble holding boost at the line? Hint: There are tons of these threads.
How many threads have you seen on here where people were asking for help with a hydroboost system trying to hold boost at the line?
enuff said.
If it was an upgrade, why would there be so many people asking what they needed to do to get their car to hold boost at the line instead of pushing through the lights?
I am in full agreement that a vacuum system is reliable. Bottom line is the hydroboost system is more complicated. It is a well engineered system though...... there are tons of Astro vans, diesel trucks, and big SUV's that use this system. We even have an old '77 GMC 1-ton with a 350 gas motor that has a factory untouched HB brake system on it. It stops like no tomorrow.....but the truck is falling apart around the chassis/running gear. This system has never given any trouble in 35 years.
Anyway......many people on here are wanting to hold boost with the foot brake at the line..... and as far as I can tell, there isn't a chance the vacuum system is better than HB in that respect.
From my experience, when driving vehicles with both types of systems....... the HB vehicles are more touchy with the brake pedal..... if you are used to driving a vacuum booster vehicle and get into a HB vehicle.... the first hit of the brakes is usually much more feeling that you are stopping with a much easier pedal effort as compared to vacuum..... but that is just me.
If you have different test data, I would sure like to see it.
I don't know what shape the PM was in in your test..... apparently not too good if the customer was looking to replace it..... but put you a pressure gauge at the caliper and see what pressure you get.... then do that with a properly working HB or PM system...... this is more of a scientific approach to answering which one has a potential to "hold" rotors or drums better.
There are going to be people perfectly happy with a properly done vacuum conversion, but these guys typically aren't trying to cut sub 1.50 60' times on a foot brake either.
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What the hell does the type of power assist have to do with holding boost at the line?
Once the pedal is pressed, the power assist job is done.
At that point it is a MECHANICAL problem, and has nothing to do with the type of assist.
I really try to avoid pissing contests based upon opinions rather than facts or personal experience, so I will just bow out of this thread, and let you spread your beliefs.
I do have a BSME in mechanical engineering, but I have learned to overcome that handicap in the real world.
