Bruce
02-02-2004, 08:51 AM
For the TR's there are 4 basic systems available.
The PowerMaster, Vacuum booster, HydraVac, and Manual.
And they all have upsides, and downsides. Explaining the upsides, and downsides, doesn't make one better or worse then the other. It just lets folks know what they're dealing with. And this board is about information, so don't confuse the messenger with the message.
So what do we have?.
We have a series of calipers, and wheel cylinders that need fluid under pressure to operate. For any given combination, you'll need x amount of fluid at a given pressure to develope maximum braking forces. The amount of pressure, and volume is a given. The system type is just what supplies those items. While the Bore diameters vary from one M/C type to the other, the operating pressures are the same.
Ups, and downs.
PowerMasters (explained simply) have an electrical pump that developes pressure to assist in lowering the pedal effort. It's compact, self-contained, and just needs electrical power to operate. Downside is that it developes alot of assist, so when it fails, there's a huge increase in pedal effort to stop the car. And an electrical problem, pump/accumulator failure can cause it to fail. But, it offers the least pedal *effort* to stop the car. Parts can be relatively expensive, and not so available, so when traveling that can be problematic.
A common replacement for the PowerMaster is just grafting the system off of a N/A, G-Body. It's rather large, and just needs a vac source to function. in the case of the *booster* failing, the effort is less then what it would be with the PM (in failure mode) to stop the car, but still takes a pretty high effort to stop the car. Downside is if the engine dies, you might only have one pedal application with *power assist*, before your in the high effort mode. Parts prices are less then the PM, and more available.
HydraVac. Very few people use these, but they are now again available at kinda high pricing. Compact, but need a supply and return line off of the Power Steering. And like the PM should it fail it takes a high effort to stop the car. Tossing a belt, having a line burst are ways for it to fail. I've never had to get parts for one, and with only one current aftermarket supplier, it would be hard to say what availibility might be like.
Then we have Manual brakes. 81 El Caminos offered what would be the oem set-up for the G-Bodies (at least according to the replacement parts catalogs). So it's an oem cross chassis transfer. So manuals can be done with the same oem engineering as the PM, and vac. There are also alternatives for the M/C from Wilwood, Mopar, etc.. They're the most compact of the systems. The only possible failure, is internal leakage, which all of the above suffer from, but it's the only failure mode. If one uses the oem parts then parts are available at any parts house. Downside is a slightly longer pedal travel, and higher effort (since there is no assist). What's often missed, or ignored is this slightly greater pedal travel, will allow you to better modulate the brake application (some people love this, some seem to hate it).
Hopefully now faced with the facts, one can choise what system is actually what they want.
If you have a race car, and there is a possibility of serious mechanical failure at high speed, then a system independent of having to have the engine running might make sense. Having the brake pedal feel like it went dead at high speeds, is not very comforting.
For an around town cruiser, then a real light effort at the expense of being able to have max braking force modulation, is often seen as a worth while choise.
For those on a budget, and not needing to maintain the oem look, then the vac system looks good. With GM having used that concept in the 89TTA, it would indicate they have a *good feeling* about vac boosters, and turbos.
The Hydravac has been pretty much ignored, but is an option.
A few more facts to think about,
No brake system is going to work 100% without maintance. Brake fluid flushing is about the most critical maintance item on a TR, and often not done. For the 87 MY the TRs were the faster thing GM offered. Yet, in comparison to the vette in second place, the brakes in the TRs are no where near as good, for being able to repeatedly stop the car, from high speeds.
As the cars get older they need more mainatnce. Brake lines, fresh fluid, constant brake inspections, should be something for things for people to keep in the forefront of their maintance lists.
If you want to run soft rear shoes, and large wheel cylinders. You may get to the stage of having a car that in LESS then Ideal circumstances, wants to swap ends in a panic stop. IF you do such things, be sure to know the abilities of your car. Dry roads, are nothing like wet roads in a panic stop, and what might be an acceptable brake balance on dry roads, might not at all be close on wet roads. Not to mention big/little tire combos.
If you do go to large B-Body Brakes, there are some secondary effects. You get a much better chamber curve, meaning that as the car leans when cornering, the outside tire tries to maintain a flat foot print better then the oem geometry. The downside is that there is alot more bump steer, meaning as the front suspension compresses the tires toe out some (in the case of TRs). So while you might be able to swerve and maintain much better control of the car, in a full-on panic stop, the front end *might* *hunt* a little. The *might* *hunt*, varies by spring shock packages.
Hopefully, that sheds some light on things.
The PowerMaster, Vacuum booster, HydraVac, and Manual.
And they all have upsides, and downsides. Explaining the upsides, and downsides, doesn't make one better or worse then the other. It just lets folks know what they're dealing with. And this board is about information, so don't confuse the messenger with the message.
So what do we have?.
We have a series of calipers, and wheel cylinders that need fluid under pressure to operate. For any given combination, you'll need x amount of fluid at a given pressure to develope maximum braking forces. The amount of pressure, and volume is a given. The system type is just what supplies those items. While the Bore diameters vary from one M/C type to the other, the operating pressures are the same.
Ups, and downs.
PowerMasters (explained simply) have an electrical pump that developes pressure to assist in lowering the pedal effort. It's compact, self-contained, and just needs electrical power to operate. Downside is that it developes alot of assist, so when it fails, there's a huge increase in pedal effort to stop the car. And an electrical problem, pump/accumulator failure can cause it to fail. But, it offers the least pedal *effort* to stop the car. Parts can be relatively expensive, and not so available, so when traveling that can be problematic.
A common replacement for the PowerMaster is just grafting the system off of a N/A, G-Body. It's rather large, and just needs a vac source to function. in the case of the *booster* failing, the effort is less then what it would be with the PM (in failure mode) to stop the car, but still takes a pretty high effort to stop the car. Downside is if the engine dies, you might only have one pedal application with *power assist*, before your in the high effort mode. Parts prices are less then the PM, and more available.
HydraVac. Very few people use these, but they are now again available at kinda high pricing. Compact, but need a supply and return line off of the Power Steering. And like the PM should it fail it takes a high effort to stop the car. Tossing a belt, having a line burst are ways for it to fail. I've never had to get parts for one, and with only one current aftermarket supplier, it would be hard to say what availibility might be like.
Then we have Manual brakes. 81 El Caminos offered what would be the oem set-up for the G-Bodies (at least according to the replacement parts catalogs). So it's an oem cross chassis transfer. So manuals can be done with the same oem engineering as the PM, and vac. There are also alternatives for the M/C from Wilwood, Mopar, etc.. They're the most compact of the systems. The only possible failure, is internal leakage, which all of the above suffer from, but it's the only failure mode. If one uses the oem parts then parts are available at any parts house. Downside is a slightly longer pedal travel, and higher effort (since there is no assist). What's often missed, or ignored is this slightly greater pedal travel, will allow you to better modulate the brake application (some people love this, some seem to hate it).
Hopefully now faced with the facts, one can choise what system is actually what they want.
If you have a race car, and there is a possibility of serious mechanical failure at high speed, then a system independent of having to have the engine running might make sense. Having the brake pedal feel like it went dead at high speeds, is not very comforting.
For an around town cruiser, then a real light effort at the expense of being able to have max braking force modulation, is often seen as a worth while choise.
For those on a budget, and not needing to maintain the oem look, then the vac system looks good. With GM having used that concept in the 89TTA, it would indicate they have a *good feeling* about vac boosters, and turbos.
The Hydravac has been pretty much ignored, but is an option.
A few more facts to think about,
No brake system is going to work 100% without maintance. Brake fluid flushing is about the most critical maintance item on a TR, and often not done. For the 87 MY the TRs were the faster thing GM offered. Yet, in comparison to the vette in second place, the brakes in the TRs are no where near as good, for being able to repeatedly stop the car, from high speeds.
As the cars get older they need more mainatnce. Brake lines, fresh fluid, constant brake inspections, should be something for things for people to keep in the forefront of their maintance lists.
If you want to run soft rear shoes, and large wheel cylinders. You may get to the stage of having a car that in LESS then Ideal circumstances, wants to swap ends in a panic stop. IF you do such things, be sure to know the abilities of your car. Dry roads, are nothing like wet roads in a panic stop, and what might be an acceptable brake balance on dry roads, might not at all be close on wet roads. Not to mention big/little tire combos.
If you do go to large B-Body Brakes, there are some secondary effects. You get a much better chamber curve, meaning that as the car leans when cornering, the outside tire tries to maintain a flat foot print better then the oem geometry. The downside is that there is alot more bump steer, meaning as the front suspension compresses the tires toe out some (in the case of TRs). So while you might be able to swerve and maintain much better control of the car, in a full-on panic stop, the front end *might* *hunt* a little. The *might* *hunt*, varies by spring shock packages.
Hopefully, that sheds some light on things.