Newbie: Brake / lug pattern question

[Q-Dog]

Before you get too excited about that new GEX engine, read through this.
https://www.thesamba.com/vw/forum/viewtopic.php?t=92079&highlight=gex
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Brian

'69 Dune Buggy
'69 Beetle Convertible
'70 Beetle

[YDBD]

The master cylinder looks like it says "Ford" on it...and it doesn't look like a VW master cylinder. Just some home engineering that worked, so not sure about the hose with the bolt.

Might I suggest a new one with new lines and hoses all around as well? I prefer the old style with the reservoir on top, but your choice.

As stated before a dual circuit adds the safety factor, doesn't effect front/rear braking bias.

Looks like you're on your way for an awesome summer project!

[wythac]

Two words. Start. Over.

Its possible that reservoir was designed to feed both the brake master cylinder and a hydraulic clutch master, much as the ones on Vanagons do. That would explain the third spigot.

[didget69]

[oprn]

A couple comments if it's ok.

If you want more braking power out of any brake system, decrease the tire radius. Shorter tires give the brakes a better mechanical advantage. Most that find the need for upgraded brakes I suspect have changed tire/wheel sizes and it is a direct result of installing taller rubber.

My Manx clone came with low profile 14" skins and it has amazing stopping power with stock drums!

The second comment is to do with matching disc brakes to the master cylinder. Braking effectiveness is not as simple as changing to discs. I put a set of type 3 discs on the front of my '71 Super Beetle back in about '74. What actually happened is the braking effort went up, the effectiveness went down and the braking bias shifted to the rear causing the rears to lock up first.
This I believe is because of the change in balance in hydraulic area ratios. The diameter of the master cylinder must be matched properly to the diameter of the brake cylinder! It has nothing to do with more volume.

When deviating from the stock system effectiveness as well as brake balance can go either way. It's a function of tire diameter, master cylinder area, wheel cylinder area, brake pedal arm length and brake shoe/pad area.

It's a science guys! Don't be changing things out willy-nilly and what works on one car may not work on another. Too many variables! When you do change things, for Heaven's sake take it out on the track or a deserted back road and wring it out to see the results. The last thing you want to do is find out the fronts lock up and slide or the rear wants to swap ends with the front in the traffic!

[paulundemma]

Thank you for the post about GEX engines. I will not go for that engine.

And I also saw the Ford logo on the cylinder, so I will replace it.
There is a 22mm early VW Bus single circuit master cylinder which should replace factory number 211611011J. This has a Reservoir.

Is this what I should go for?

[wythac]

To the OP, who I believe is looking for some specifics:

This is what I run on my buggy. Stock dual circuit M/C with a Rabbit reservoir and Wilwood residual pressure valves to account for the different requirements of the front drum and rear discs on a swingaxle car. With a full cage and other add ons, my buggy isn't that much lighter than a stock beetle. With two people in it, likely about the weight of an empty bug.

It works well. Much thought and some trial and error occurred before I settled on this configuration. Nothing "willy-nilly" about that, or the results; Under full braking, its good that I have seat belts with a submarine strap. With 31" tires on the back. And I tow a trailer.

None of this is uncharted territory. Much more data in the Beetle forum but monkeying with brake bias is more of an offroad baja and buggy thing.

Brake master cylinders are cheap and easy to swap out if you don't like it. If you want a single circuit Bus M/C, buy it and install it. If you don't like it, go out and get a dual circuit from a beetle. Other than bleeding the system, it likely wont take you more than an hour or two.

I can see you have a lot to work on, so I wouldn't tunnel in on this particular issue at this point of your build. I'd recommend that you do what's cheap and closest to stock for now. Change it when it rolls if you are unhappy with it, that is, if other projects on the car haven't sucked up the financial bandwith reserved for upgrades.



Good luck with your project.

[didget69]

Use a dual circuit master from a later Beetle & new brake hardlines. This would be the best time to upgrade the brake system.

bnc
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I never found the need to impress people with any mechanic certifications, trophies or track wins... unless it was for Mom to post on the refrigerator door.

[Singerdude]

Congrats on the new buggy and welcome to the Samba.

Drums on all fours will be more than enough braking for a stock engine.

But... Spending any time here and reading threads from a bunch of guys that have 100, 150 even 200 HP engines, you'll soon find out that it is kinda hard to resist the appeal of power

I couldn't

So if you think you might get sucked in the whole bigger displacement thing, discs will absolutely become a must, so you might as well go discs now.

Anyway you do it, you are in good hands here, the folks on this forum are a helpful and resourceful bunch.

By the way is the KXF yours? I rode dirtbikes for a long time, did amateur MX races for a bit. Now I get my adrenalin fix by ripping twisty country roads in my buggy and the bike sits in the garage most of the time. Ah damn! Now that I talk about it, it makes me want to ride again

Good luck with the project and I hope you can get it rolling soon.

[oprn]

[paulundemma]

[Singerdude]

[911pickup]

While you have the body off I'd recommend installing all new lines and a new dual master cylinder.
If you plan on installing front disc brakes I'd also recommend installing a brake line residual pressure valve.

Here's a photo of my new master cylinder, new lines, and residual pressure valve (blue color).
I also installed a disc brake kit in the front and rear.

[hillmotorsports]

911pickup
I'm curious about your combination....
Disc brakes at both ends yet needs a residual valve?
What master/reservoir combo is that?
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Rosemarie and Paul Hill
Morrisburg, Ontario

(With way more projects than spare time!)

[wythac]

oprn,

Dunno where you got the idea that what you think I wrote required that kind of reply; You took a rather specific, qualified statement that I made about where the OP will find more information, and made a response indicating that I was offering up advice akin to the automotive equivalent of running with scissors. You've stated your concern twice now about how you are afraid we are going to be careless or are offering careless advice. Nothing the original poster says indicates that he is going to be careless...give him, and us, some credit. This is not the VW 101 forum for most.

We can take this conversation offline if you'd like. This thread is about providing the original poster some hardware solutions and examples specific to a dunebuggy build. Please do that.

[paulundemma]

Hi, me again. Need advise again.

We have been working on our buggy, basically it ended in a full rebuild...

New floorpans, new motor, new paint, new link rods, steering box (not on pictures), new everything. New mastercylinder incl. reservoir, new lines, disk brakes up front and originally I was planning to keep drums on rear (with an adapter) and just rework them. Pattern of wheels is 4x130.

Now: Opening the rear drums they have a different wheel cylinder which is bolted with 2 screws and not with 1 as the 1964 drums should be. According to the web this used on older bugs (55-57)?

Why is this? Any reason someone would convert to this? Or is our chassis older than what is in the title?

What do we do now?
Use the older type wheel cylinders or spend money and do disk brakes also?

Any advise is welcome!

[cdnltded]

[EVfun]

Some small details in your frame shots tell me the frame is not older than '58. It seems unlikely those rear brakes belong on it (about 2 months of early '58 cars still had oval type brakes.)

Now that you are 4 lug up front it could make sense to put '68 up brakes out back. They are wider (and 4 lug) and you have a choice of rear wheel cylinders. You can run stock or swap to larger bore front wheel cylinders if the stock brake ballance results in the front brakes locking too easily.
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[paulundemma]

I felt I post an update after more than 1 year building...I believe 95% done. Painted, seats installed, it drives, brakes, steers, horn works, lights work. Some detailing still to do.

[EVfun]

That is a clean looking build. Your look captures the simple essence of a beach buggy.
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