Brake upgrade report

[dan@angband.org (STENDEC)]

OK, this is long, so grab a cup of coffee before reading.  Also, bear
with a few little explanations I put in, I'm also posting this to a local
car group, and not everyone there is VW-familiar.

So here's my report on the brake conversion I did on my Scirocco this
weekend.  The lowdown: Went from 9" solid discs in the front to
10.1" vented ATE powerdiscs, with the funky spirograph shaped
slotting.  Went from worn-out pads of unknown origin to Ferodo street
pads. In the rear, went from drums with worn-out shoes to 8.9" discs with
stock ATE pads.  Added stainless steel brake lines all around, and went
from a the stock 20mm master cylinder to a 22mm, because the
10.1" calipers need more volume. (more on this later.)

The first giant pain in the ass was installing the new brake hoses in the
rear.  There is a short 6" line that goes over the trailing arm mount.  It
is a moderate pain to access on the left side, but on the right, it it a  
complete bitch.  Access is severly limited by the gas tank and fuel
pump.  I ended up having to use a cutoff wheel to cut a few inches off my
flare nut wrench, and had to use my MAPP torch to bend a box wrench into a
funny shape to get at the brake line nuts.  It took maybe an hour each to
replace these stupid hoses.  If I had to do it again I'd probably
remove the trailing arm first. The rest of the rear installation went
pretty smoothly, I had to replace the stub axle to add caliper mounting
points, reroute where the brake line from the top of the axle to the
bottom, and install new parking brake cables. (more on this later too..)

Compared to the rear, the front was a breeze.  Unbolt old pad carrier
and caliper, and install new ones.  The ATE powerdiscs say they come with
a new kind of anti-corrosion coating that does not need to be removed
before installation, but I did it anyway.  Three cheers for chlorinated
solvents. The powerdiscs are kind of neat looking, the groove is not as
deep as I was expecting, but it is only supposed to go as deep as the wear
limit of the rotor.

Now, the next pain in the ass.  The 22mm master cylinder I had was out of
an Audi, it is an ATE cylinder made of cast aluminum.  So, I bench bled
it, and was installing the proportioning valves (They are little
cylindrical in-line units for the rear brakes) when i overtightened one,
heard a terrible snap, and saw that I had cracked the MC casting.  I then
took 10 minutes and cursed a whole lot, but at least I refrained from
throwing any tools.  At this point, it was 7:30 on a saturday, and I had
no wheels to go looking for parts anyway.  Instead I did some research
with my ETKA disc. (VW microfiche on CDROM.)  The stock MC used for this
brake combination has a stoke of 17mm primary, 15mm secondary, so I needed
a MC which could displace this volume or greater.  The stock MC is kind of
hard to findm because it is used only for the Scirocco, for 2.5 model
years. A VW Corrado/late model Jetta/Golf MC is 16mm/18mm, and often used
becasue it is cheaper and easier to find, while still having a bit more
volume than the stock MC. But, I found one even better.. from certain
early '90s Audi 80/90s, 22mm bore, 19mm/17mm stroke.  Extra volume
is always a good thing, plus, it I ever go to 4-piston calipers (which I 
doubt I will), I'll have the volume I need.  I also found another
interesting MC ... 20.64mm bore, 19mm/17mm stroke.  Run the numbers, and
you'll find it has a tiny bit less displacement thant he stock 16v
cylinder, (like 2% less..) but the smaller diameter piston means you get
more PSI availible.  I decided to pass on that one for now, but it might
make an interesting experiment for someone.  BTW, if anyone needs the
part numbers for any of these, let me know.  Might make a good addition to
the FAQ?

Next morning, I went to our 2 local pull-a-part junkyards, did not find
any 22mm master cyls.  Did see one of the long-stroke 20mm cylinders I
mentioned, but it looked really crufty, someone had pulled the reservoir
and it looked as if it might have gotten water inside it. Went to my
Friendly Local Auto Parts Store, they did not have any of the MC's I
needed in stock, and their computer was down so they could not query other
stores.  If he did have the Audi MC I wanted, it would be $106 (rebuilt,
lifetime warranty)  I showed him my cracked MC, and I guess he took pity
on me, because he gave me the phone number of the distrubutor they bought
their MC's from.  I called them, they had it in stock, I just had to
drive a half hour to their warehouse. Also, it was a cast-iron unit, so
dumbasses like me were unlikely to crack it by overtightening fittings.

So I took it home, installed it, used my homemade "Cheapass Ron" style
pressure bleeder,  and bled the system really well.  The pressure
bleeder rox, btw... everyone should make one.  Takes maybe 5 minutes to
do a complete flush and fill.

REALLY firm pedal feel, those stainless lines rock.  Only slight hitch was
hooking up the parking brake cables... I got them off a Jetta GLI, and
they are just a hair too short.  I was able to get one of the adjusting
nuts on, but there is no room for a locknut.  I'll live with them for now,
maybe put a drop of locktite on the nut.

Did a couple other little maintainence jobs... Replaced the front motor
mount becase it was pretty much destroyed, adjusted the exaust pipe so it
didn't rub on the swaybar, and replaced my swiss-cheese airbox with a
stock one, because it pretty much sucked.

Brakes feel awesome so far, nice firm pedal, no noise.  I haven't made
any agressive stops yet, or heated the brakes up from multiple stops, want
to let the pads bed well for a bit.

Well, this was longer than I intended.  Hope someone found it
useful/entertaining.

Dan





-- 
What a waste it is to lose one's mind. Or not to have a mind is being very
wasteful. How true that is.

		-- Dan Quayle