Porsche 356 Master Cylinder in 55-63 Split Bus?

[desertbus]

Hi. I looked through the TheSamba archives and could not find my specific needed answer there. So I thought I'd start a new thread to see if I might can find the answer I need that way.

I have a 1962 Kombi with its original drum brakes. It has been my daily driver since 1990. Of course the front brakes of '62 buses have small diameter drums (as compared to 64-67 larger one-ton drums).

My brakes are not really stopping me well. They do alright on level ground. But on the downhill they can be scary. In spite of resurfaced drums, new pads, new everything, my bus just does not like to stop on a dime, on flat ground or otherwise. I instead have to really add a lot of pressure to my brake pedal to get my brakes to pay attention.

My own research about this reveals that some early-year split-bus owners who still have stock brakes on their heaps use Porsche 356 master cylinders, specifically part number 69535501100, for better braking action. As near as I can tell from my research that particular master cylinder has a shorter stroke, which apparently makes for higher pressures, which makes the brakes grab better with less effort when the brake pedal is pushed on.

From this thread http://www.thesamba.com/vw/forum/viewtopic.php?t=245981&highlight=porsche+356+master+cylinder I found this...


"The MC bore diameter and the stroke are extremely important when using
a MC with a specific system. For instance, and most folks do not know
this. The early 3/4 ton bus MC `55-`63 is different then the 1 ton `64-`66
MC as well. According to Bentley..single circuit MCs...

Early
22.2 mm Bore
30 mm stroke

Late
22.2 mm Bore
36 mm stroke"

So, apparently anyway, if I want to stop well I need a 30 mm stroked master cylinder in my early bus. And from what I've been reading most Empi, etc. split-bus master cylinders are the 36 mm stroke version. And so the reason my bus isn't stopping so well is probably because I likely have the 36 mm stroked-type of master cylinder in my '62 bus right now.

Anyway, here's my question. Has anybody else here used the Porsche 356 master cylinder part number 69535501100 on their bus? Does it have the correct 30 mm stroke for early buses? And did it help?

Does anybody here have any wisdom about this topic they'd like to share here? I want to keep my bus stock if at all possible. But I also want my bus to stop well enough to keep it from getting any more dents in it.

Oh, before I forget, does anyone know of a brake pad relining business that uses friction-rich linings that might make for better stoppage (as compared to the usual replacement pads)?

Thanks for any help you can provide.
_________________
Love is blind; Friendship closes its eyes.

1962 Kombi Frankenbus (has a 78 Westy poptop)
1966 Kombi Frankenbus (has a 78 beam)
1968 Euro Westy (nice and original)

[Eric&Barb]

Stroke is not going to make one iota of difference in power of braking. Diameter of bore and of course matching piston will.

Get the 1971-79 bus MC installed. For all the brake cylinders inspect, clean out, and use brake paste to keep corrosion away for as long as possible. Get your brake drums adjusted right and checked that the drums are not worn out. Then you certainly should be able to lock up the drums on dry pavement, maybe not easily, but you can. If you have a bad leg, etc.. look into a vacuum servo to give an assist.

The one ton brakes also have wider brake shoes on front and rear for 20% more braking power. Really if you want to get more braking power you will need to step up to the one ton parts or go with after market disc brakes.
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In Stereo, Where Available!

[sled]

you should have no trouble coming to a very abrupt stop, even on a hill, with properly adjusted 62 drum brakes.

you said you had your drums turned, did you have the shoes arc'd correctly to the newly turned drums? arc'd shoes makes a HUGE difference.

make sure there is ZERO air in the brake system, this will result in a spongy pedal and less than ideal braking.

Eric or Barb, is right about the stroke making zero difference.



but, yes it is a good idea to upgrade to a dual-circuit master cylinder, its just not the Porsche one you need. a '67 bus master will fit the bill
_________________
drive your split.

[Eric&Barb]

[desertbus]

Thanks, Sled, for the mention of getting my shoes arc'd. I didn't know such an option existed. I have researched further and discovered that arcing brake shoes is an almost lost art at brake shops these days. Apparently arcing fell out of favor with workers comp insurance providers a couple or more decades ago due to the fear of asbestos dust, and most brake shops have since gotten rid of their arcing machines as a result. But it turns out that only about a mile from my home is Arizona Brake and Clutch, which still has an arcing machine. In fact, they're apparently well-known among collector car groups for still offering the arcing of shoes. So, judging by the lack of friction rub on my current near-new rear shoes, my goal at this point is to take my four spare big nut drums to them, let them pick out the best two of the four, get those best drums turned, and then get a new set of shoes arc'd to mate with them. And if that works out well I'll get the fronts done after that. Thanks, again!
_________________
Love is blind; Friendship closes its eyes.

1962 Kombi Frankenbus (has a 78 Westy poptop)
1966 Kombi Frankenbus (has a 78 beam)
1968 Euro Westy (nice and original)

[sled]

very good news! as you mentioned you noticed, new shoes that have NOT been arc'd have a small contact surface and take a LONG time to wear in (if they don't glaze first). Not arcing the shoes does two things..you can glaze or prematurely burn your shoes because they are trying to stop with such a small friction patch. two, when you press the brakes it actually makes the shoe flex. if you can imagine the pivot point of the adjuster, and the wheel cylinder applying pressure on the other side, the shoe will bend to fit the arc of the drum. If the shoe is the same arc as the drum, pressure will be even.

that being said, the front brakes do the majority of the braking, so you should have the FRONTS done first if nothing else, but all four should be arc'd.

properly arc'd shoes will give you a more solid pedal feel as well.
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drive your split.

[desertbus]

I'm going to do the rears first because I have four spare big nut drums and a set of new shoes for two of them sitting in my garage right now. So since all I need to do is drop off those drums and shoes, and then come back later to pick them up, I figured I'd just do that rear set first. I'll get the front small-drum ones done sometime after that. So all four is my plan, just two at a time.

I did read in my follow-on research that I can get a roll of adhesive-backed coarse-grit sandpaper, stick it to the inside of the drum, and then literally sand the shoes to match the inner curvature of the drum myself. The only issue with that is the width of the sandpaper itself making the actual resultant curvature lf the shoe-pads being made a little more curved than the actual curvature of the drum. Anyway, seeing as how there is a business that is only a mile from my home that will do this for not too expensive of a price, just this once I'm going to break from my usual of doing everything I can myself and instead let someone else do the task.
_________________
Love is blind; Friendship closes its eyes.

1962 Kombi Frankenbus (has a 78 Westy poptop)
1966 Kombi Frankenbus (has a 78 beam)
1968 Euro Westy (nice and original)