davygrvy
Has anyone ever added a power booster like this to the front circuit?

http://www.mpbrakes.com/products/product-detail.cfm?product_id=221

I'm contemplating mounting one in the bonnet. Run a vacuum line down the tunnel to the manifold..

Front discs are in (topline kit). The metering and adjustable prop valve will get added next week to prevent the current nose dive and better weight transfer for high speed panic stopping. Type3 rear conversion happening next week as well.
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MY72BUG
I can't say I have ever heard of anyone adding power assist to Beetle brakes.  And with that kind of cost and trouble and the addition of such a long vacuum line I would be much more inclined to go 4 wheel disc if intensive stopping is your goal.
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YELLRHD
Unless you have gone with some way over the top brakes you shouldn't need much more than the stock master cylinder.

That booster would be a waste of dollars you would not be able to pull enough vacum to get it to work and it is over kill for a car as light as ours.


The later model M/C which you should already have in your 1303 is more than adequate for the disc brake conversion. I'm inclined to think you may have problems with your rear set up as is if the front is taking over and diving.

You shouldn't need a proportiong valve either I would make sure you car has the correct M/C first and then make sure your rears are up to snuff.


I am running the disc front / drum rear at the moment and it works very well
I ran all discs in my previous 1303 and it was about the same you have to be doing some serious track time to generate enough heat for brake fade.
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davygrvy
YELLRHD wrote:
Unless you have gone with some way over the top brakes you shouldn't need much more than the stock master cylinder.


But what if I don't want to press so hard like in any modern power everything compact?

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That booster would be a waste of dollars you would not be able to pull enough vacum to get it to work and it is over kill for a car as light as ours.


The dox say 17" of vacuum for full output.  Yes, I should test it.  Length shouldn't matter.  Volume of the tubing might.

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The later model M/C which you should already have in your 1303 is more than adequate for the disc brake conversion. I'm inclined to think you may have problems with your rear set up as is if the front is taking over and diving.


Try this with a disc converted beetle with no valving.  Take a highway cross-over ramp with a relatively tight and banked radius at speed and jam it hard on the turn.  I had to do that for a real panic stop in the first beetle I converted to disc.  The weight shifted too heavy and too fast to the fronts and I nearly lost it.  After putting in the proper metering (hold-off) in the front and adjustable proportioning valve in the rear, the same location test panic stop (yes, no one was behind me) was a complete success with no nose dive and funny weight shift.

That was my first disc beetle.  This is my second.

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You shouldn't need a proportiong valve either I would make sure you car has the correct M/C first and then make sure your rears are up to snuff.


Add the pair and you'll see what you're missing in terms of stability and safety.  The downside is the metering valve require more pedal pressure for the same stopping force, so it ends up feeling like the original drums, but now the harder you press the harder you stop unlike the drums.

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I am running the disc front / drum rear at the moment and it works very well.
I ran all discs in my previous 1303 and it was about the same you have to be doing some serious track time to generate enough heat for brake fade.


Discs in back make no sense to me.  After the onset of weight shift, your fronts do all the work.
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olspeed
davygrvy
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But what if I don't want to press so hard like in any modern power everything compact?

Well I think the hole question here it how much do you want to spend? Do you want a race car? Last time I put in a proportiong valve was on our race car. These cars are anywhere from 30 to58 years old or older. The way they drive and handle can be improved over stock in many ways. Some of the changes just enhance the driving experience and some change it completely. I have to admit I liked to climb in to our 71SB with a full cage,discs all around,proportion valve, cutting brakes and a line lock. But the car also had a 165 vair motor, power-glide trans, and rode on 14" tires with 2 1/2" sheet rock screws in them 350 per tire.
My point is I like to climb in to my 66 Ghia an cruise around, I don't have to much traffic worry about"just some big ### moose". If you want to up grade your Bug To Race car standards that is fine, "I know how bad traffic can be as I kiss the nearest road way when I come back up here from vacation in the lower 48". Espesially if the motor is pumped up, extra brakes are necessity. But these are old cars I for one am not looking at my ghia as a
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any modern power everything compact
If that is what you are looking for that is great and I would like to see some posts,that way I could decide what improvements I might do to mine.
Olspeed
66 Ghia, "Dexter" 76 flat window Beetle
It's not a Car it's a VolksWagon!
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davygrvy
For what it's worth, here's the parts list for the blue 73 super of mine:

1) front disc conversion.
2) metering (hold-off) valve for the front.
3) adjustable proportioning valve for the rear.
4) 2psi residual valve for the front. (probably not needed)
5)10psi residual valve for the rear.
6)braided stainless flex lines for the rear.
7)Type3 rear drum conversion.

Not all of it is installed yet.  But my other Super has the same setup.  The squareback rear stuff should be coming by UPS today or so.  I got them off a guy on theSamba.

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davygrvy
olspeed wrote:
Well I think the hole question here it how much do you want to spend? Do you want a race car?


No race car required!  Not this Bug.  This car is my daily.  The issue isn't cost per se.  I don't mind dropping $500 for a power booster and the work to install it.  Just wondering if anyone has done this before.

Ok, looks clear no one has.  So if I can get 17 inches of vacuum over a 12 foot tube off the manifold, looks like this'll do the trick to lessen pedal effort.

Wish I had a '75 or '76 instead for rack&pinion..  power steering could be possible
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Sleepwalker
I have not done this either, but, in my line of work I deal a lot with vac/air cfm/pressure.
If you are going to pursue this, as it sounds like you are, I would suggest you use Polly-Flow tubing to do it.
Or better yet get some hard line tubing like you would use for brakes for the main run. This way you don't run the risk of collapsing of the tube just when you need it most.
Only other thing I could bring up is the fact that you may indeed get 17 foot pounds of vac through the normal 1/8" hose, but that is going to fall off to about 6 pounds at 1/4" tube.
And, I'm not sure if you are going to be able to maintain the volume that is required to to activate it consistently, as your VAC is dependent on the draw through the carb(s),
not going to be as much sitting at the street light, if it was your Dizzy would be advanced all the time (for those of us that have VAC advance units)

"He who knows enough to learn, knows enough"
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davygrvy
Sleepwalker,

First, thanks for the advice on hose type.  This stuff, right?  I was thinking standard 1/2" oil hose.

No, I won't be using the vac feeds on the carb.  First off, the vac signal for the dizzy is NOT the manifold.  The manifold one already goes to my aircleaner for the pre-heat diaphram.  My aluminum manifold already has a blocked-off bung on it for such a need.  This photo of it makes me laugh as it's turned around backward.  The bung is on the right side in the photo.  Actual dizzy-side installed.



Also, like any older american car, manifold vacuum is used for the booster with a one-way valve on the booster itself so assist isn't lost when you're on the gas.

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YELLRHD

One thing about weight transfer
The way your suspension is set up can have some effect on this as well.
On my last car it dove quite handly when the front suspension was 30 year old stock components but after upgrading with Toplines stuff it handled quite well without any additional components.
Not to mention like ol speed said everyone drives differently I may have had the same problem had I been in you situation with my car but not having been there I can't speak to it.

I can under stand the residual valves and proportioning control would come in handy if your set up requires it and it is a cheaper route I would try those first and see if you can get want you want out of them.

Its just the thought of spending almost 500 bucks for a power unit that no one has tried before without knowing if it will solve your problem.

There are many brake set up threads over on germanlook.com that cover the whole gamut from drums through extreme set ups it may be worth the time to read through them.

I'm sorry if if my first post came across wrong it would still be interesting to see how this works in the end. On what Sleepwalker suggests I think a metal line for the longest run would work best or better yet an electric vacum pump that way it could be close to the booster and eliminate a loss due to line volume etc......

The power steering idea has been brought up I just cant seem to remember where I think the idea was to use the electric power steering from a modern Honda??? or one of the hybrids. The rack and pinion from 75 and later supers can be fitted to earlier supers there are many threads on it in the various forums. I have found the R&P supers do steer a lot easier and probablly do not need power assist due to the steering geometry but I've been without power steering for so long I don't miss it any more.


Sorry for the long post

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Sleepwalker
Yep, forgot about the check valve, good point
as far as tubing this is what we use SMC
Should be about the same as what you posted
"He who knows enough to learn, knows enough"
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olspeed
An electric vacuum pump is probably the best but in the medium truck market 3 to 10 ton they do use vacuum assist brakes. As diesels don't produce vacuum you might check out the belt driven vacuum pumps that they have available. If I remember right one for a early 90's ford 5 ton with a 7.3 IHC is about $150.00. Although you could probably get one with pulleys and mounts from a junkyard for cheaper.
Olspeed
66 Ghia, "Dexter" 76 flat window Beetle
It's not a Car it's a VolksWagon!
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davygrvy
There's an electric pump option too.  I really don't want to go that route or an engine mounted crank-driven pump either.  I'll see if I can grab a vacuum gauge at my FLAPS and test what manifold vacuum I get as is.
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