Power booster size??

Anyone using a 7 inch power booster in their Nova? I have an 11 inch and I have a line on a 7 inch with the master all in chrome for a great price. I was wondering if there is any down side to using a 7 inch and not an 11 inch like whats in the car now.

Thanks

I have a 7-inch booster from a Chevette in my 66. If you were to compare the diaphraghm area you would find that the 11-inch has considerably more.

I thought it would be about the same due to the volume. The thickness of the 11 inch is not thick as a 7 inch..

Hopefully an expert will chime in. I'm not him. I do recall, there is a difference between a single and dual diaphram. If the 7" is a single, I believe it will be insufficient. If nobody can help on this site, call MP Brakes. http://www.mpbrakes.com/

The pressure is applied to the diaphraghm, and the amount of pressure is related to the area of the diaphraghm. The 11" unit would have an area over twice that of the 7" one. In my 67 the 7" booster was quite sufficient as I had very good intake vacuum. If the single diaphraghm setup is insufficient you can get dual diaphraghm units.

An animation:

http://auto.howstuffworks.com/power-brake2.htm

This would be good information to know.....

So, you're saying that if the 7 inch was a dual diaphragm it would be as good as an 11 inch? By the way, the one I'm looking at is a dual diaphragm.

The pressure is applied to the diaphraghm, and the amount of pressure is related to the area of the diaphraghm. The 11" unit would have an area over twice that of the 7" one. In my 67 the 7" booster was quite sufficient as I had very good intake vacuum. If the single diaphraghm setup is insufficient you can get dual diaphraghm units.

An animation:

http://auto.howstuffworks.com/power-brake2.htm

So, you're saying that if the 7 inch was a dual diaphragm it would be as good as an 11 inch? By the way, the one I'm looking at is a dual diaphragm.

The 11" diaphragm ( finally spelled it right ) is more than twice as large as the 7". You can approximate the relative area by squaring the radius. 3.5 squared is about 12.25, so you'd get about the same results with a 7" dual as a 10" single. Not exactly, but roughly.

Yup, got it.. So the 7 inch dual should work fine as someone stated in this post I think. So, it looks like I'll get the one I was looking at to swap in..

Now not to but in here, but wouldn't a 7" single power booster be better than a manual set up? Also from what I've seen on the site we have a few people still running manual with plenty of stopping power as far as they are concerned. An 11" would be easier to push to the point of locking up the brakes, but I think you could still lock them up pretty easily with a 7" booster considering I was able to lock the brakes up in a 69 GMC truck with 4 wheel manual drum brakes. Granted I felt like I was trying to push my foot through the floor boards!

More info, I contacted the guy and found he also has this setup in chrome with an 11 inch booster so, I'm all set :D

Yes, a 7 inch single booster when compared to a non-power setup would be much better hands down. I have had many cars that came with non-power and then converted them over to power. I don't care how good anyone thinks their car stops, when they convert to power brakes they would see what they were missing..

Now not to but in here, but wouldn't a 7" single power booster be better than a manual set up? Also from what I've seen on the site we have a few people still running manual with plenty of stopping power as far as they are concerned. An 11" would be easier to push to the point of locking up the brakes, but I think you could still lock them up pretty easily with a 7" booster considering I was able to lock the brakes up in a 69 GMC truck with 4 wheel manual drum brakes. Granted I felt like I was trying to push my foot through the floor boards!

I don't care how good anyone thinks their car stops, when they convert to power brakes they would see what they were missing..


If all you did was add a booster to make your car stop better, maybe you should hit the gym more often! Without changing the size of the brakes, or the lining material, or something, it's only going to make a difference in the pedal pressure--not stopping ability.

BS!! You ever try and stop a 4,000 lb car without power then convert it to power??? You don't know what you're talking about.. The ability to stop a 4,000lb car with and without power brakes is like night and day dude!!

If all you did was add a booster to make your car stop better, maybe you should hit the gym more often! Without changing the size of the brakes, or the lining material, or something, it's only going to make a difference in the pedal pressure--not stopping ability.

BS!! You ever try and stop a 4,000 lb car without power then convert it to power??? You don't know what you're talking about.. The ability to stop a 4,000lb car with and without power brakes is like night and day dude!!

Now correct me if I'm wrong here, but the master cylinder is what controls the pressure to brake calipars and cylinders. The pressure is a responce to the amount of pressure the rod going into the MC sees. Brake pads can only apply a give pressure to the rotor or drum before lock up occurs and this is based on the surface area of the brake shoes or pads. A booster amplifies the input rod force on the out put rod force. Thus if you can apply enough force to the little rod going into the MC to lock the wheels up you have achieved as much braking as you are going to get! Does not matter how you get enough pressure on the rod (ie manually, through a booster, through an air compressor, or anything else you can dream of) you have achieved as much brake as you are going to get for that stop. Bigger pads will create more friction at a given pressure making it easier to get to lock up and you save a little wear as the wear is spread out over a larger area and the heat produces has a larger area to dissapate into. The distance your foot has to travel also changes based on length of lever travel required. If this is what you are calling better braking then due to physics I would have to say you are in error. It still takes the same amount of energy to stop a 4000 lb car whether it has manual or power brakes. It just takes less from the driver when you have power brakes and supliments it by using wasted vaccum.

I'd like to interject here for a second...

My '72 nova has freshly rebuilt 4-wheel manual drums. Sure, discs would stop better...but I have had absolutely zero problems with stopping with my 4-wheel manual drums; I do notice some fade while aggressively stopping from high speeds.

I'm not a big guy, or a "tough" guy so to speak, but I can lock up my 4wheel manual drums without trying all that hard.... HOWEVER! My girlfriend occasionally drives my nova around and complains about the pedal pressure. She can still lock up the brakes (without really standing on the pedal) but would like a much softer pedal.

I've asked this question before, but slickman--you say you've converted a few manual drum cars to power?
I'm wondering what all is involved with the swap... Just add a booster? Or is a new master cylinder required as well?
Thanks, and sorry for the small hi-jack.

If your just going for power brakes and not disc then you will need a booster and you will need to alter your brake lines going to the booster. You may need to get a couple small extension pieces for your brake lines. One other thing is the rod that goes from the pedal into the Master Cylinder or booster when going to power. I've heard of some using the origional with no problem and then others have to make an adjustable set up to get the length of the rod right. Ultimately if your not very good in the fabrication department (ie bending lines and messing with linkage) you might be better off getting a complete front power disc brake conversion kit since most kits include a step by step instruction manual and all the parts needed.

Listen, I was a mechanical engineer for 13 years and if you want to debate Mechanical inertia with me, I'll go toe to toe with you.. If power brakes are a waste of time then I guess all of the cars made today need YOU to reevaluate the design because they all have power assisted brakes.

I guess you are MUCH more knowledgeable then me and all the engineer's at the big three..:rolleyes:

By the way, lockup is NOT only based on pressure, the weight of the car plays a heavy weight on when that happens, not just the pressure.

And if you want to sit there in a panic situation and stand on the pedal to get it to stop from 70mph, more power to ya.. I'll stick with my power option and stand behind what I stated.

When you go to power brakes, you see what you have been missing and is superior to manual..

Now correct me if I'm wrong here, but the master cylinder is what controls the pressure to brake calipars and cylinders. The pressure is a responce to the amount of pressure the rod going into the MC sees. Brake pads can only apply a give pressure to the rotor or drum before lock up occurs and this is based on the surface area of the brake shoes or pads. A booster amplifies the input rod force on the out put rod force. Thus if you can apply enough force to the little rod going into the MC to lock the wheels up you have achieved as much braking as you are going to get! Does not matter how you get enough pressure on the rod (ie manually, through a booster, through an air compressor, or anything else you can dream of) you have achieved as much brake as you are going to get for that stop. Bigger pads will create more friction at a given pressure making it easier to get to lock up and you save a little wear as the wear is spread out over a larger area and the heat produces has a larger area to dissapate into. The distance your foot has to travel also changes based on length of lever travel required. If this is what you are calling better braking then due to physics I would have to say you are in error. It still takes the same amount of energy to stop a 4000 lb car whether it has manual or power brakes. It just takes less from the driver when you have power brakes and supliments it by using wasted vaccum.

Not a problem. I did not say you can't lock up manual brakes, what I did say was when you convert to power you will see how nice it is and also "what the hell did I wait for".. Now, I have converted a few cars over to power. 55 Chevy, 69 Road Runner, 66 Mustang and 71 Camaro.

If you're car is all drum, all you need to do is swap in a booster. If you are also changing the fronts over to disk, you need to make sure you also change out the master and not just install a booster. The manual drum master has a larger piston size and if you just install a booster without a new master the brakes will be way to sensitive..

I'd like to interject here for a second...

My '72 nova has freshly rebuilt 4-wheel manual drums. Sure, discs would stop better...but I have had absolutely zero problems with stopping with my 4-wheel manual drums; I do notice some fade while aggressively stopping from high speeds.

I'm not a big guy, or a "tough" guy so to speak, but I can lock up my 4wheel manual drums without trying all that hard.... HOWEVER! My girlfriend occasionally drives my nova around and complains about the pedal pressure. She can still lock up the brakes (without really standing on the pedal) but would like a much softer pedal.

I've asked this question before, but slickman--you say you've converted a few manual drum cars to power?
I'm wondering what all is involved with the swap... Just add a booster? Or is a new master cylinder required as well?
Thanks, and sorry for the small hi-jack.

Can someone explain to me how reducing the required pedal pressure (vacuum power assist) changes the effectiveness of the braking system?

Can someone explain to me how reducing the required pedal pressure (vacuum power assist) changes the effectiveness of the braking system?

I think that's what this whole arguement about...

Ultimately, not much...but it'll make the pedal easier to depress, making it easier for you to modulate the pressure on the brakes, and easier to lock up the brakes. I can't possibly see how something such as a brake booster, that only helps you depress the pedal, will make brakes any more or less effective--just easier for the average jo-schmo to use.

You are CORRECT!!

I think that's what this whole arguement about...

Ultimately, not much...but it'll make the pedal easier to depress, making it easier for you to modulate the pressure on the brakes, and easier to lock up the brakes. I can't possibly see how something such as a brake booster, that only helps you depress the pedal, will make brakes any more or less effective--just easier for the average jo-schmo to use.

You are CORRECT!!

So power brakes don't make the car stop any better, just easier on the person trying to push the pedal! I thought that is what I had said in a round about way!

So you were a mechanical engineer for 13 years! How did they take the title away? I'm an Electrical Engineer that unfortunately gets stuck doing a lot of boring Mechanical Engineer work on large steam turbines.

Also since I work for Siemens I have had a little time discussing the new Electronic wedge brakes in development at Siemens VDO with the engineers developing it. This is probably going to be the next evolution in automotive brakes. Through talking with them if my Nova is ready when they are for the creation of conversion kits for older auto's I might be able to get my car in on the Alpha or Beta level of conversion kit testing. Some of the testing performed was very interesting. At one point they spun a heavy rotor up to 500 RPM then using hand pressure tried to stop the rotor by pushing conventional brake pads against the rotor using a jig that simulater how the pads would contact the rotor in a calipar set up. Then we did the same thing with the wedge pads, with the same surface area as the convetional pads, designed like the new system will use. It took less than half the time to stop the rotor with the wedge set up. Only thing I don't like about the whole set up is that it will use a computer when actually put into use.

That's cool.... I got out of the mechanical engineering field about 20 years ago. Got laid off from Bayer and the industry was taking a down turn so, switch over to a Senior Purchasing agent of property goods (Castings, Injection molds, Structural foam, sheet forming, and others). Did that for 9 years and then the industry took another bad turn. Now I have been a IT specialist for the past 12 years..

It pays the bills :D

So power brakes don't make the car stop any better, just easier on the person trying to push the pedal! I thought that is what I had said in a round about way!

So you were a mechanical engineer for 13 years! How did they take the title away? I'm an Electrical Engineer that unfortunately gets stuck doing a lot of boring Mechanical Engineer work on large steam turbines.

Also since I work for Siemens I have had a little time discussing the new Electronic wedge brakes in development at Siemens VDO with the engineers developing it. This is probably going to be the next evolution in automotive brakes. Through talking with them if my Nova is ready when they are for the creation of conversion kits for older auto's I might be able to get my car in on the Alpha or Beta level of conversion kit testing. Some of the testing performed was very interesting. At one point they spun a heavy rotor up to 500 RPM then using hand pressure tried to stop the rotor by pushing conventional brake pads against the rotor using a jig that simulater how the pads would contact the rotor in a calipar set up. Then we did the same thing with the wedge pads, with the same surface area as the convetional pads, designed like the new system will use. It took less than half the time to stop the rotor with the wedge set up. Only thing I don't like about the whole set up is that it will use a computer when actually put into use.