[T2] Can disc master cylinder be used with drum brakes?

[david raistrick]

the caliper in that empi kit APPEARS to be the same style as the kit CSP
uses.  I'm sure someone by now has figured out what caliper that crosses
over to...   but that's just going but the one picture.

the rotor looks like the old CSP rotor design - the current CSP rotor
appears to be a two piece now, so you can just buy the rotor hat (and WW is
selling just the parts now, yay).

ah I found a thread where woody installed a set - definitely appears to be
a two piece hub+rotor assemby.  so worse case a -good- parts shop (or a lot
of digging through rotor catalogs) can find you a replacement in the future.


personally I'd be super skeptical of anything EMPI sells these days.  the
era of empi being a source of quality parts was a really long time ago.  I
can't think of a single positive thing I've heard about them in recent
history....  "cheap, but it broke" or "cheap, but I had to make it work"
comes to mind.


I will make this comment:  if I were doing it again, I'd (probably) get a
15" only kit and get wide 5 15" wheels instead of sticking with my 14s.   a
bigger rotor with more swept area would be a nice positive..   not to
mention opening up more rear disk options.  (You actually have some rear
disk options on your bay anyway)




On Thu, Jul 2, 2020 at 2:26 PM Warren McKean <warren.p.mckean at gmail.com>
wrote:

> God I love corresponding with someone who has done all this great
> research. The EMPI kit is 22-2940 (
> https://www.jbugs.com/product/22-2940.html). They seem to have put
> together the most complete kit I have seen. What I don't like about it is
> they don't tell you whose caliper they are using and it won't work with
> drop spindles. The MC has no residual valves so they include one to insert
> into the rear brake line.
>
> On Thu, Jul 2, 2020 at 10:27 AM david raistrick <keen at icantclick.org>
> wrote:
>
>>
>> so the residual valves on all the bus MCs that I've seen (keep in mind
>> it's been a lot of years now since I last dug into this) are external.  so
>> they're easy enough to remove (or gut).
>>
>> you definitely need residual valves on the drums - but any VW bus master
>> from any era is going to have that already because everything was always
>> rear drum.   even if you use a rabbit MC, it's also going to have rear
>> drums, so it'll have residual valves.   you'd be up into A4 golf land (99+)
>> to get a 4 wheel disc MC that wouldn't have resid valves...
>>
>>
>>
>> for front discs - I don't really think a residual valve is a good thing
>> at any level.  there are no springs pushing things back, so you'd just be
>> using that residual pressure to hold the pads against the disc....
>>
>>
>> as for 1 2 or 4 piston calipers - for a bus, it really doesnt matter
>> (really).  (if you've got a 2liter in a split and you're heavy on the loud
>> pedal, it might matter....but not really).    1 piston calipers are always
>> floating calipers, though - so that's actually a real positive for daily
>> driver types.   what it means is that the caliper slides on a bracket and
>> -always- self centers (as long as the slides dont bind from lack of
>> maintenance and lube).    4, and usually 2 piston calipers, are fixed
>> calipers - you HAVE to shim and adjust them to center and square.   if
>> you're off a little bit, you'll get reduced brake force on the inside or
>> outside pad and uneven wear.
>>
>> but our choices are limited (unless you're designing a kit yourself), so
>> it's kind of a "take what you can get" set of options.
>>
>>
>> I think the most important part of any disk brake selection is going to
>> be wear-item availability.  pads and disks and caliper piston seals.    So
>> a caliper that has fitment to a known vehicle (98 golf, etc) or from an
>> known aftermarket mfr (wildwood, etc) is really important - both from a
>> long term ownership standpoint and from a "can I adjust this with different
>> pad compounds if I dont like it".       Discs are harder - but a full size
>> or cut-down 944 disk, or a mustang 2 disk that has a machined seal surface
>> are things you -can- buy again and get any machine shop to make fit for you
>> later.   well, the full unmodifed 944 disc doesnt even need that. :)
>>
>>
>> I dont recall that EMPI had an option when I last looked - so not sure
>> what they're using.  Send me a link and I'll take a look when I get a
>> chance.
>>
>>
>>
>>
>>
>>
>> On Thu, Jul 2, 2020 at 12:35 PM Warren McKean <warren.p.mckean at gmail.com>
>> wrote:
>>
>>> David,
>>> Thank you for this info. I read your analysis of the 4 disc conversion
>>> kits plus other sites on the internet. There seems to be some agreement
>>> that either a 2 lb residual valve or no valve is recommended for discs and
>>> a 10 lb residual valve is recommended for drums. Since I will have front
>>> discs and rear drums I would need a master cylinder with no residual valves
>>> and install a 10 lb valve in the brake line to the rear drums. What do you
>>> think?
>>> Do you have an opinion of the advantages of getting a 1,2, or 4 piston
>>> caliper? And did you look at the EMPI kit?
>>> Warren
>>>
>>> On Wed, Jul 1, 2020 at 12:56 PM david raistrick <keen at icantclick.org>
>>> wrote:
>>>
>>>> yes.
>>>>
>>>> but you can also use the drum master for the disks.   for aftermarket
>>>> disk conversions, this is usually the better choice anyway.  (I've written
>>>> a lot about this in the past....)
>>>>
>>>>
>>>>
>>>> On Wed, Jul 1, 2020 at 3:47 PM Warren McKean <warren.p.mckean at gmail.com>
>>>> wrote:
>>>>
>>>>> Gents:
>>>>> I have a 1970 Baywindow (bought new). I plan to upgrade to front disc
>>>>> brakes soon, but have an immediate need for a master brake cylinder.
>>>>> Can I
>>>>> use the brake cylinder that will be necessary for the front discs with
>>>>> my
>>>>> existing front/rear drums? Also, since most folks install discs in the
>>>>> front only, does the 1971 brake cylinder have a retention valve in the
>>>>> rear
>>>>> hydraulic line?
>>>>> Warren McKean
>>>>> 1970 Camper
>>>>> _______________________________________________
>>>>> type2 mailing list
>>>>> type2 at type2.com
>>>>> https://www.type2.com/lists/type2/listinfo
>>>>
>>>>