[VB] disc brakes next - potential winter project

[david raistrick]

On Thu, Aug 17, 2017 at 9:59 AM, Kevin Guarnotta
<kevin at guarnottadesign.com> wrote:

> Some stuff /questions I've come across
> 1.Vented vs non-vented. Seems like vented is only a little bit more, so I'll probably go that way.
> 2. Size - I see some listed as 5x130 and 5x205, I guess the 5 indicates the number of lug nuts, and the 205 or 130 is the space between the lug nuts? What is the stock size?

for our purposes - 5x205 is stock wide 5 beetle/bus/etc.  5x130 is
porsche.  5x112 is late bus/vanagon/etc.   4x...something bigger than
100... is late beetle.


> Has anyone done this, and regretted it? Anyone use a kit they didn't like? Anyone use a kit they thought was relatively easy to install, and works well?


I have the wagenswest babystang - they clear 14s.

stock '65 wheels are 14s (14x5).  1955 to 12/63 were 15" (15x4.5).
1/64 - the end of the vanagon were 14 (excluding some vanagon alloys,
but those might have been 14 too)


 the babystang and bustang (bustang clears 15") and many others use a
wilwood caliper (most common aftermarket mfr with excellent mfr and
3rd party support for pads and parts, including knockoffs) .   if
wilwood ever goes away, 3rd party pad mfrs will still sell pads.

The nice thing about using a wilwood (or clone) caliper is that there
is significant amounts of technical data for them, and -many- various
pad compounds to choose from, complete with dyno charts (heat vs brake
force) for those compounds.  This is also true of 944 pads, but no 1st
party data on pads, only 3rd party.


from memory, sago uses a wilwood knockoff.  csp uses an undisclosed
and possibily proprietary caliper (though more info may have been
released)


the babystang uses a mustang II rotor with minimal modification - the
grease seal opening is machined to fit a bus grease seal.   in theory,
you can get any mustang II 9" rotor (cheap as dirt and super common in
the hot rod aftermarket), find any automotive machine shop to open
them up, and have a new rotor.   these are vented.   also available
drilled, slotted, cryoed, and pretty much any other worthless value
add treatment available for brakes.. :)     off the shelf bearings are
used to fit the rotor to the hub, and a modified 944 grease cap is
used.

I don't recall what the bustang uses, but it's a larger rotor also
from a mustang generation.


vented vs solid:  for fronts, you really do want vented.   that said -
in a split bus, getting enough heat into the fronts can be a problem,
so maybe it doesnt matter as much.

slotted/drilled - have zero value in our application and only weaken
the rotor.   slots "allow gasses to escape between pad and rotor
during high heat applications"  and drilled "helps cool rotor and pad"
- except, real road race cars dont use them....   motorcycles and
bicycles do drilled, but that's because of the weight reduction.


any of the kits are decent enough - just unbolt everything off the
spindle, bolt up the new, bleed and go.    2, 4, and 6 piston calipers
are used in various kits and require a bit more work to bleed.


on the master:  you absolutely should switch to a dual circuit master.
  in my researched opinion, the best option for this is still the '67
master.  this is available in repro these days for reasonable money.
    it's the closest to appropriate piston size for the fronts, and
delivers good volume.   there might be some early rabbit and volvo
masters as well, but they dont bolt straight in the same way...

people will argue using a disk brake master - completely ignoring the
fact that a disk brake master piston size was designed for a booster.


wheel adapters:  most options will involve running a wheel adapter.
that's OK.   a lot of cars run them from the factory and you dont even
know it - dodge ram 3/4 and 1 ton trucks.  porsche 944s run them up
front.    The differences are in the quality of the adapter. :)   If
you're using a mustang rotor, you'll be adapting 5x4.5 to 5x205.  if
it's a porsche rotor, it'll be 5x130 to 5x205.  if it's a vanagon
rotor, it'll be 5x112 to 5x205.


track width:  all options change the track width a bit.  some narrow
it, some widen it.  if you're running 15x4.5's your track width is
already a little different than if you ran 14x5s.    Generally, the
vendor can tell you how much it changes (+.5" or -.5" or whatever) and
you can judge if your tires will still clear inside and out before you
install it.   Handling change will not be noticable (in a bus).



on my babystangs - I had two significant problems.   1) the pad
compound Nate sent was entirely inappropriate for the heat generated
in a split camper.  that is to say, it never actually comes up to
temperature in daily driving use.   you need a cold-oriented pad.   I
was able to find an alternative compound and that drastically improved
things.   2) the caliper sat a little to close to the spindle, causing
the pads to "ride" on the joint between the rotor surface and the hat.
This caused the outside pad to be effectively useless since it didnt
grab the rotor.  I used some measured washers to find 4 washers that
spaced the rotor out the same distance on both sides to clear, and
that helped.


On all of these that use fixed (instead of floating) calipers:  You
want to make sure to "center" the caliper any time you loosen/tighten
it.   basically, have it loose enough to wiggle, then have your helper
apply brake pressure (or use a reversed friction clamp under the
floor...), that will center the caliper based on the rotor.  tighten
while pressure is applied.   there are many many long threads on
hotrod forums about failing to do this.... :)



if I were buying again:  I'd call/email russ at oldspeed.   last time
I talked to him, he uses a 944 rotor for his 14" and 15" kit - he
basically cuts the rotor down to around 9" to fit in the 14" wheel.
still uses a wilwood caliper.   From the stuff I've seen, his overall
quality of the kit is better though.  I dont know what compound he
supplies. :)


I'd also recommend reading the threads on thesamba - there is a LOT of
data in there, some of which was supplied by me... :)


For me - with the powerlite caliper and 7912 style pads, switching
from the BP-10 compound to the Polymetric E compound was a good
impovement because of increased 100-500 degree braking power.   over
500 they're not as good.   maybe if I were braking down mountains all
day long I'd want something else.


Also:  DO NOT expect drastically better braking or less pedal effort.
   A well tuned set of front drum brakes with just broken in german
shoes will out perform any non-power options available that will fit
inside our wheels.   the 15" options might be a bit closer than the
14" options.    That said - you'll get consistent performance over the
life of the brakes, instead of having to adjust them twice on a long
road trip....     my babystangs with the PolyE compounds are
definitely close performers now.     You're generally also still going
to be limited by the front tire grip.    Pedal effort will NOT
decrease, and in fact will be harder - drum brakes "add" power at
speed as you apply pedal pressure, it's not a linear increase (because
the drum pulls the shoe into a wedge..there are some good videos out
there on this).   with discs it's straight linear effort.

Switch to discs because you are tired of adjusting them, or because
you never actually bought good german shoes so you dont know what a
good set of drums can really do, or because you dont like the price of
those shoes, or because you're tired of wheel cylinder failures.  :)



anyway - ask away, I've got a ton of notes around this stuff if you
want to know about any particular options.


oh - the 944 bolt on conversions: if you're only with 15s only, that's
by far your cheapest option, even buying new calipers/rotors (NA
calipers/rotors are pretty cheap).   but then you also need 5x130
adapters and I dont know what the track width change is...)

Figure somewhere in the $1500 for a kit, otherwise.   Money well spent, IMO.