Disc Brake Conversion
By Ryan Ballou
In this article
we break from our theme of engine tech to cover something just as important
as gong fast, being able to stop going fast. For some reason we all seem
so focused on making more power, being quicker, going faster, but what
good is any of that if you can't come to a controlled stop? So we turn
to the experts, Top
Line Parts located in Anaheim, CA for a front disc brake conversion
kit. Top Line has the well-earned reputation of being the 'go to' place
for Super Beetle specific needs for over 25 years.
There are quite a few advantages to running disc brakes, some aren't even
well known. The most obvious benefit is improved braking power and control.
Discs are much less prone to fading as they heat up. Under heavy use,
drums will dramatically lose stopping power as they begin to overheat.
Discs are self-cleaning by design, allowing them to shed dirt and water,
unlike drums. One of my favorites, discs are self-adjusting, no need to
crawl under the car every few months (still need to adjust rear drums,
though less often), and your pedal engagement height will remain more
constant.
Now the more obscure benefits. While these particular discs weigh about
the same as the drums they are replacing, the weight distribution is much
better. A great deal of a drums weight is in the outer ring that makes
up the contact surface. With disk brakes, this ring is moved inward and
essentially becomes an integral part of the hub. Even though the weight/mass
is virtually the same, the moment of inertia (rotational mass) has been
decreased through mass redistribution. The benefit of this is much like
running a lightened flywheel; it will take less power to spin the rotors
up, leaving more power to push you down the road. This redistribution
also serves to lessen the effects of imbalance within the rotor, a common
problem in the drums I've seen. This design also allows the rotor to be
more rigid than it's drum counterpart. Greater rigidity means less chance
of distortion from rims that aren't perfectly straight. Add these two
things together and you'll find a design that can seriously help alleviate
the problem know as the Super Shimmies.
My first impression of the kit was simply, wow, this has everything. My
biggest pet peeve when taking on a project is having to stop because you
need to make a run to the shop for parts. Not so in this case, the only
things you'll need are normal shop supplies like brake fluid, brake cleaner,
and wheel bearing grease. The kit includes Ghia rotors and calipers (pre-loaded
with pads), making replacement parts a breeze to find. Top Line's trick
billet aluminum caliper adapters indexed for right and left hand sides.
Also included are a complete set of SKF wheel bearings, grease seals,
stainless steel braided Teflon brake lines and pair of brake line holders
to keep you lines clear of moving parts.
Time to install these bad boys. First thing's first, pop the front hubcaps
and break the lug nuts/bolts loose on both front wheels. Now you'll want
block the rear tires, put the car in gear with e-brake on, and jack up
the front end under the frame head. I found it easiest to leave the key
in the ignition to prevent the steering lock from engaging, this way you
can pivot the spindles by hand allowing better access to them.
Remove the wheels and set them to the side. The drums are removed by prying
off the dust caps and removing the spindle nuts under them. The spindle
nuts are a special clamp design and require a 6mm Allen wrench to un-clamp
them before they can be removed. Don't mix the left and right side up;
the right side (pass) has normal threads, but the left (driver) uses reverse
threads. This is a safety mechanism so that if the Allen bolt fails, the
direction of wheel rotation will keep the nut from backing off, and your
wheel from falling off. Set the nuts and the keyed washers under them
aside with the wheels and dust caps. You may want to bag them to keep
dirt and debris from sticking to the grease on them.
With the spindle nuts off, you can now pull the drum from the spindle.
You may need to back off on the shoe adjustment a click or two if the
drums were worn severely and the shoes are catching on them. Most likely
the inner bearing and seal will remain on the spindle so gently pry them
loose and set them back in the drum for now. Now remove the four bolts
holding the backing plate on, but keep them nearby. If you pull the clip
on the strut housing that holds the brake line in place, you should be
able to pull the whole backing plate off the spindle and hook the hard
line at the slave cylinder over the tie rod out of the way. By keeping
this assembled for now, you won't be dripping brake fluid on the ground
until the end of the project.
Take a few minutes to lightly sand or scrape any rust or gummy buildup
off the mating surface of the spindle where the caliper bracket will sit.
This needs to be clear of debris so that the bracket will seat flat against
the spindle. Clean up all the grease off the spindle now too. You can
wipe off most of the old grease with a paper towel or shop rag, then give
it a good final cleaning with some brake cleaner and clean rag. Take a
few minutes to clean each of the bolts you set aside. Discard the washers
that came off with them and use the new wavy washers provided by Top Line
to attach the caliper brackets. These are labeled RH and LH for right
hand and left hand respectively. They mount so that the caliper will be
towards the rear of the car. Go hand tight at first, then torque to 40
ft*lbs. in two steps (20 ft*lbs. first) in a crisscross pattern.
Time to prep the rotors by installing the bearing races in the hub. This
is a lot easier than it sounds. First make sure the inside of the hub
is clean, you don't want anything preventing the bearing race from fully
seating. You'll need to dig out two different size sockets, one for each
bearing race. They should fit the opening in the hub with as little play
as possible and ride on the lip of the race, not on the taper. Socket
ODs vary with manufacturer, but I found a 1 1/8" (29mm) and 1 7/16"
(36mm) to work best for me. Set the race in the hub and lightly tap it
around it's perimeter to get it started. Then set the socket on it and
keep working it in. Go slow and make sure the race goes in straight. If
it starts cocking to one side, work the other side a little. Keep at it
until it is firmly seated in the hub. Do a quick visual to make sure there's
no gap under it.
Once you've installed the inner and outer races, clean inside the hub
again by blasting it with brake cleaner. Next, blow out the inner (larger)
bearing with brake cleaner to remove the light oil coating on it. Pack
it well with bearing grease and set it in the race. Smear a little grease
around the outside edge of the grease seal to help it slide in without
tearing and tap it in like you did the bearing race, using the socket
if need be. Don't drive this home, just make it flush. Turn the disc over
and set it on a clean paper towel or other lint free rag. At this point
I like to pack a layer of grease inside on the walls of the hub leaving
just enough room for the spindle. This acts as a reserve and when it heats
up with use, will soften and mix with the grease in the bearings, assuring
they always have grease around them. Now clean and pack the inner (smaller)
bearing and set into it's race.
Keep your finger over the outer bearing to prevent it from falling out
and slide the whole assembly onto the spindle. Try to keep the spindle
out of the grease you just packed into the rotor by going as straight
as possible. Follow up with that keyed washer (clean it first), and finally
the spindle nut. For now just turn the nut down until there is minimal
play in the bearings and lightly tighten the Allen bolt.
Before moving on to the caliper, thoroughly clean the contact surfaces
of the rotors now. Just keep going at them with clean rags and brake cleaner
until when wiped down with a clean white rag, no signs of dirt are seen
on the rag. You may also want to attach the brake hoses now while the
calipers are still easy to work with. Remove the spacer from between the
brake pads and set the caliper into position. Use the 10mm bolts and wavy
washers that are provided to attach the caliper. Screw them in hand tight
and watch for clearance between the end of the bolts and the disk as you
tighten them further. I found that I needed to grind about .050"
off the end of each bolt or they would bind on the rotor. When you are
sure they will not interfere, use a dab of anti-seize on each bolt and
torque them to 50 ft*lbs.
Now you can disconnect the old rubber brake hose from the hard line and
set the assembly off to the side. Attach the new brake hose, but cinch
it down just yet. Put the brake line holder on the strut housing and attach
the clip to the brake line so that the hose is between the wheel and strut.
Reinstall the wheels now and tighten the lug nuts/bolts as best you can
with the car still jacked up. Pivot the wheel assembly as though you were
turning the steering wheel from stop to stop, and make sure the brake
line doesn't rub the tire. It may rub a little at the spring perch, but
try to keep it from touching anything through it's full range of motion.
Once done, tighten the clamp and the connection to the hard line and reinstall
the clip at the hose to hard line connection.
Now with the wheel back on you will need to make the final adjustment
to the wheel bearings. Grab the wheel with a hand on top and a hand on
the bottom and push/pull alternately to check for play in the bearing.
Tighten the spindle nut until you can no longer feel play in the wheel,
then back it off until just a little play is felt, then tighten the Allen
bolt. Now pop on the dust caps and you're done. I found that my dust caps
were a little too tight no matter how hard I banged on them. I made a
few passes at the dust caps with a die grinder and they went perfectly.
I took such a small amount off that it could probably be done with some
240 grit in a minute or two.
One last thing, you have to bleed the brakes now. Follow the usual procedure,
e-brake adjustment backed off all the way and rear drums adjusted properly.
Start at the passenger rear tire, then drivers rear, passenger front,
and then drivers front. The calipers used in the kit are a universal (left/right)
design and therefore have bleeder screws on top and bottom. You only need
to bleed from the top screw. Since the calipers are new, the fluid that
comes out of them at first will be dark and contaminated. Bleed them until
no air bubbles can be seen and the fluid runs clean. Readjust your e-brake
and check for a good solid pedal feel. If the pedal doesn't feel right,
check the rear drum adjustment first. If that doesn't work then do the
bleeding procedure over again. Don't forget to do your final torque on
the lug nuts/bolts, 90-95 ft*lbs. in a crisscross pattern.
When you go on your test drive after installation, understand that it
will take a few miles of stop and go traffic before the pads seat in properly
to the rotors. Until that happens you may not have full braking power.
You will also want to keep an eye on the adjustment for the spindle nuts
for the first 500 miles or so. With new bearings and rotors, things will
tend to seat in a little and you'll need to readjust to take up the slack.
Just take it easy at first, and then when they're 100% get out there and
let 'er rip.
I've had about a week now with the new brakes and I'm nothing but impressed
with them. Did some driving in the rain and they worked flawlessly despite
driving through some deep puddles. I've put them through their paces in
some holiday stop and go traffic where I'd normally start feeling my old
brakes fade a little, not even a hint of it with the discs. The pedal
feel is absolutely great. It's like driving a new car! Until
next time - drive it like you stole it.
Special thanks
to:
Top Line Parts
2910-A East Miraloma Avenue,
Anaheim, CA 92806 USA
Phone (714) 630-8371
Fax (714) 630-6477
Email info@toplineparts.com
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