Pelican Technical Article:
Five-Lug Rear Wheel Conversion
old Bee Jay has again roped me into helping him work on his 914, the freshly painted and
upholstered Non-Leaky Tikki. It looks so good
now, he just couldnt stand to run the Minilite knock off wheels any more. (The wheels arent held on with knock-off
hubs, they are cheap reproductions of the Minilite magnesium wheels.) So, we converted his rear hubs to accommodate
five-lug wheels. This article will show you
how to cobble together a makeshift tool out of inexpensive pieces from the local hardware
store, and use it to reseat the hubs. Even if
you dont want to change hubs, you can use this procedure to remove and replace rear
wheel bearings. Rookie mechanics, be aware
this is not an elementary procedure. It is
less complicated than a transmission rebuild, but definitely not a good first project.
There are several reasons to convert
a 914 from the four-lug to the five-lug wheel pattern.
Most folks do it for the sake of appearance classy Porsche and
aftermarket alloys fit the five-lug pattern. It
can also benefit performance. Many of the
five-lug wheels are wider and lighter than those available in the four-lug pattern. There are also many high performance brake
components that are compatible only with five-lug wheels.
The actual conversion entails swapping the four-lug rear hub for a five-lug
hub. Sounds easy enough, but it seems the
entire rear suspension must be disassembled to get access to the hub. OK, I exaggerate, but you will see everything that
must be removed and re-installed during the conversion.
The other complication is the rear
wheel bearing. The bearing is a press fit into the trailing arm, and supports the hub. It is a sealed unit that lasts 100,000 miles with
no maintenance. The problem is, driving the
hub out of the bearing trashes the bearing. Driving
the hub back into the bearing can also trash the bearing, if you dont do it right. The trick is to pull the hub into the bearing by
exerting force only on the inner race of the bearing.
Using a mallet to whack the hub into the bearing transfers excessive loads
through the inner race and balls into the outer race.
This fatally damages the bearing.
are three reasonable choices for converting the rear hubs to the five-lug pattern. The first way is to use 914-6 hubs. This is a very sanitary approach, but it requires
installing 914-6 stub axles, also. The 914-6 stub axle is unique to that model, but the
914-6 hub is the same one used on 1969-1973 911s (part number 901.331.065.09). The 914-6 used 28-spline hubs and stub axles;
914-4s used a 37-spline configuration.
second option is to use hubs from a 19701971 914-4, and have them drilled and
spot-faced to accommodate five-lug studs. The
1970-1971 pieces are desirable because they have bosses cast into the hubs in the right
places to support the five-lug pattern. This
gives good support to the studs and makes the finished hub very strong. There is no need to change the stub axles. Bee Jay wisely chose this option.
third choice is to use hubs from a 1972-1976 914-4. These
have no bosses for the five-lug pattern studs. The
studs will therefore be mounted into thinner metal than on 1970-1971 hubs. However, garages that have done this conversion
report no problem with the hubs failing. Again,
the existing stub axles can be used.
addition to the hubs, you will need brake rotors that are drilled for five lugs. You can order new 914-6 rotors, or have 914-4
rotors redrilled. Bee Jay bought the 914-6
rotors because his existing rotors were in poor shape and couldnt be reused.
New parts you will need:
- 2 Brake
rotors (914-6 or redrilled 914-4)
- 4 Rear brake pads
- 2 Hubs (drilled for five lug)
- 2 914-6 stub axles (ONLY if you
use 914-6 hubs)
- 10 Wheel studs
- 2 Wheel bearings
- 2 CV joint gaskets (forget these
and the CVs sling grease all over)
- 2 Cotter keys (for castle nuts
holding the hubs onto the stub axles)
- 2 Five lug wheels (you will
probably want two more for the front!)
- 10 Lug nuts
Tools and supplies you will need:
- ½ all thread (This
is a steel rod, ½ in diameter, that is threaded its entire length. It is available at your local hardware store,
usually in 3-foot lengths. You actually need
about 15 inches.)
- 2 nuts and 4 washers (to match the all thread)
- Socket set (1/2 drive, ¾ drive also
- 30mm (or 1 3/16) socket
- Long, stout flex handle to match 30mm socket
- Torque wrench
- Screw drivers
- Metric combination wrenches
- Metric hex (Allen) wrenches
- 12-point CV joint wrench
- 3 outer diameter (OD) iron pipe, or a socket the same size
- 2 OD socket, ½ or ¾
- Iron bar or pipe, 1.5 OD
- Molybdenum disulfide grease
- Anti-seize grease
- Blue Loctite
cotter key from stub axle castle nut.
|[Click on Photo]
2. Set parking brake. Loosen stub axle castle nut. This baby is 30mm across the flats, but a 1
3/16-inch socket also fits beautifully. The
nut should have been torqued to 217 to 253 ft-lb, if the previous mechanic followed the
specs. If he grabbed a pneumatic impact
wrench and got medieval on the nut, theres no saying how tight it is. I have a ¾-inch
drive socket set that helps in situations like this.
If jumping on the end of the flex handle (see photo 1)
doesnt loosen the nut, feel free to put a four-foot cheater bar (pipe) over the flex
handle and stand on the end. Needless to
say, Im not a fan of using impact wrenches to tighten nuts.
youve got the flex handle out, loosen the wheel lug bolts.
the front wheels, jack up the rear of the car, and rest it solidly on jack stands.
the lug bolts and wheels. Stash the wheels
under the car. That way, you dont trip
over them, and if the car slips off the jack stands, it crushes the wheels rather than
the castle nut and washer from the stub axle.
the parking brake. Disconnect the parking
brake cable from the lever on the brake caliper (see photo 2).
the brake pads. To do this, pull the clips
holding the pad retainer pins. Back off the
venting clearance on the inner and outer pads. Venting
clearance is the space between the brake pad and the rotor when the brakes are not
applied. On 914s, you can (actually, must)
manually set venting clearance because the rear brakes arent self adjusting (mainly
because the parking brake is integrated into the caliper).
To back off the venting clearance on the outer pad, remove the plastic cover
over the adjusting screw and loosen the lock nut. Use
a 13mm box wrench. On the outboard adjusting
screw, insert a 4mm hex wrench and turn the screw clockwise to loosen the venting
clearance. Yes, I know this sounds backwards. The inboard adjusting screw is accessible through
a hole in the trailing arm. Remove the plug,
insert a 4mm hex wrench in the adjusting screw, and turn it counterclockwise to loosen the
clearance. If you still have the old inboard
plugs with the hex wrench hole in it, I strongly recommend buying the new plugs that have
a raised hex head, so you can use a 10mm socket to remove them. The plugs tend to stick, and the tiny internal hex
hole strips out when you try to remove them. A
pair of new style plugs costs about $10. Now
drive out the pad retainer pins, remove the centering spring, and pull the pads out.
the brake caliper. The service manuals say
you need to disconnect the hydraulic brake line first, but you dont. What you need to do is to remove the clip that
holds the brake line to the bracket on the trailing arm.
It is located about a foot forward of the caliper, right where the flexible
brake hose meets the rigid line (see photo 3). Then you can remove the two bolts holding the
caliper, using a 19mm box wrench and penetrating oil.
Dont let the caliper hang from the flex hose; support it on a block of
wood or hang it with a piece of wire.
10. Remove the
two flat head screws holding the brake disc in place, and remove the disc (see photo 4). These
screws are often grossly overtorqued, and are hard to remove. A hand impact screwdriver is very helpful. This is a heavy screwdriver device you hold
against the screw, and whack with a ball peen hammer.
The impact forces the screwdriver blade against the screw and gives it a
tiny but forceful twist. Great for removing
stubborn screws. Everyone who works on old
cars should have one.
11. Remove the
three bolts holding the dust shroud inboard of the brake disc (see
photo 5). Use a 13mm box wrench and a
squirt of penetrating oil like Liquid Wrench. These
bolts may have been installed 30 years ago! Your
hub should now look like photo 6.
Note that Bee Jay had installed aftermarket wheel studs on his four-lug
hubs, instead of using the stock lug bolts.
12. At this
point, the service manuals say you need to remove the heat exchangers, which is a royal
pain in the gluteus maximus. The heat
exchangers prevent removal of the axle half shafts, which must come out to pull off the
hub. The ever-resourceful Bee Jay figured a
way to remove the half shafts without dropping the heat exchangers. Read about it in the next step.
13. Use the
special 12-point CV joint wrench to remove the four bolts holding the constant velocity
joint to the transmission flange (see photo 7). Remove the half shaft by pushing the stub axle
out of the hub. If you chose not to remove
the exhaust system, you will find the inner CV joint hits the transmission, trapping the
stub axle in the trailing arm and preventing you from removing the half shaft. Relax, there is a simple trick to get the stub
axle completely clear of the trailing arm. On
the right side half shaft, push the inner CV joint forward and upward, and you will gain
enough clearance to pull the stub axle completely out of the trailing arm (see photo 8). The left
side is more difficult. On the left side of
the transmission, the starter occupies the space that Bee Jay pushed the inner CV joint
into on the right side. So, disconnect the
battery ground, disconnect the cables to the starter, and remove the starter. You now have enough space to push the inner CV
joint up and forward, and the stub axle will clear the trailing arm. Bee Jay believes removing the starter is a lot
less hassle than dropping the exhaust system. Decide
14. The next step is to drive the hub out of the wheel
bearing. There are fancy and expensive
pullers to do this, but they are hard to use on a 914 because the trailing arm offers few
flat surfaces to push against. The normal way
is to use a 1 ½-inch outer diameter steel bar or pipe, and drive the hub out from the
inside. We used a 1 ½-inch outer diameter
(OD) socket and an old, beat-up extension (see photo 9). If you use a new extension for this task, it will
soon look old and beat up. Removing the hub
requires repeated heavy blows with a big hammer (see photo 10),
because the hub tends to corrode and glue itself to the bearings inner race. The violence of removing the hub will destroy the
bearing. We removed the right side hub with
little trauma, but the left one just wouldnt budge.
I applied Johnsons Law (dont force it - use a bigger hammer) but
I still got nowhere. So, we used a 13mm box
wrench to remove the four bolts holding the bearing retainer cover, and continued beating
on the hub. We figured we would push the
bearing out of the trailing arm with the hub, then we could worry about freeing the
retainer cover. What happened was, the
bearing broke apart and the hub came out with half the inner race, the retainer cover,
balls, and cage attached. Bee Jay pried the
cage from the hub. The cage came off easily,
ball bearings flew all over the garage, and the bearing retainer cover was free. We werent going to reuse the hub or bearing
anyway, so we were happy. Apparently,
corrosion had permanently cemented the inner bearing race to the hub, making it impossible
to remove the hub by itself.
15. If you
managed to drive out the hub without loosening the bearing retainer cover, remove the
bearing retainer cover now. A 13mm socket or
box wrench will do the trick (see photo 11).
16. Remove the
bearing from the trailing arm. The easiest
way is to pound it out from the inside, using the Brute Strength and Ignorance (BS&I)
method. Crawl under the car and put a 2-inch
OD steel bar or pipe against the inner bearing race. We used a 2-inch OD socket and
extension (see photo 12). Note
how the socket is reversed on the extension, so the narrow end of the socket self-centers
in the bearing. Now, grab a ball peen hammer
and drive the bearing outward (see photo 13). Dont worry about damaging the bearing,
youve already reduced it to scrap iron by removing the hub.
17. Clean up the
trailing arm with degreaser. The recess on
the inside, where the CV joint lives, is usually caked with old grease and mud. The bearing retainer cover will also need a bath
in grease solvent. The seating surfaces for
the bearing must be very clean so the new bearing mounts properly. My old buddy, Jim Alton, swears by Gunks
18. Install the
new bearing. Bee Jay cooled them down in the
freezer overnight, prompting his lovely bride to ask if we were going to defrost bearings
for lunch. Freezing causes the bearings to
shrink slightly, so they slide into the trailing arm easier. Squirt the seating surface in the trailing arm
with WD-40, take a bearing out of deep freeze, and drive it into the trailing arm with a
3-inch outer diameter pipe. Dont
dawdle, or it will warm up and expand. I
actually used a big socket and a mallet to drive the bearings in (see
photo 14). DO NOT drive the bearing in by
hammering or pulling on the bearing inner race, or you will trash the bearing! Make sure you line up the bearing squarely to the
seating surface in the trailing arm, and it will go right in. As the bearing warms up, water will condense on
it. Dry it off, and wipe the exposed surfaces
of the bearing with WD-40 to prevent rust.
19. Install the bearing retainer cover with four bolts and
washers. Clean up the bolts and threaded
holes with lacquer thinner or brake cleaner, put a drop of blue Loctite on the bolts, and
torque them to 18 ft-lb.
20. Install the
hub. Before you do this, verify the retainer
covers are in place. If you install a hub
without the retainer cover, you will have to remove the hub, thus destroying the bearing,
before you can correct your mistake. (Not
that anyone writing a tech article would ever make a mistake like that!) We pulled the hub into the bearing with a cheap
collection of ½ inch diameter all-thread, nuts, washers, and sockets (see photo 15). The
socket on the inside of the trailing arm pulls against the inner race of the ball bearing
ONLY. This socket should have a 2-inch outer
diameter. The socket on the outside of the
trailing arm pushes against the hub. Its
diameter isnt critical, as long as it seats squarely against the hub. We used a 1 ½-inch OD socket. Smear the
all-thread with molybdenum disulfide grease where the outer nut will run. I like to spritz a bit of WD-40 on the mating
surfaces of the hub and inner bearing race, to avoid the corrosion that caused us problems
(see step 14). Assemble everything finger
tight, and make very sure the hub is square to the bearing. Then, crank down on the outer nut with a box wrench
(see photo 16). You
will have to hold the hub so it doesnt rotate.
Figure 1 shows a cross-section of the trailing arm, bearing, hub, and
installation hardware, with the hub halfway installed.
The hub will be drawn right into the bearing inner race without damaging the
bearing. Slick! Disassemble the all-thread and socket contraption,
and admire your new five-lug hub (see photo 17). The hard part is over.
21. Install the
half shaft. While the half shaft is out,
its a good time to repack the CV joints with molybdenum disulfide grease, and check
the boots. This should be done every 30,000
miles. Use a new gasket where the CV joint
mates to the transmission flange, and torque the bolts to 31 ft-lb. If you are using 914-6 hubs, you need to install
the 914-6 stub axle on the half shaft, or it wont fit into the hub!
22. If you
removed the heat exchangers instead of following Bee Jays recommendation, install
them now. Use new gaskets where the exhaust
pipes mate to the head, and smear the mounting studs with anti-seize. If you followed Bee Jays advice, install the
starter and cables.
23. Smear a dab
of anti-seize on the stub axle threads, and install the washer and castle nut. Dont use molybdenum disulfide grease here;
it is so slippery under high pressure, you will overtorque the nut. You can torque the nut to about 50 ft-lb now, just
to get everything seated.
24. Install the
brake rotor. The flat head screws should be
torqued to 3.6 ft-lb, which is just snug. A
drop of blue Loctite will keep them from loosening, and will prevent corrosion in the
threads. We found the holes in the 914-6
brake rotors didnt match the threaded holes in the redrilled 914-4 hubs, so we
couldnt install the flat head screws. No
big deal, the lug nuts will hold everything together.
25. Install the
brake caliper. The steel mounting bracket for
the dust shroud is sandwiched between the caliper and the caliper mounting lugs on the
trailing arm. Put some blue Loctite on the
caliper mounting bolts, and torque them to 50 ft-lb.
You will probably need to use a crows foot to torque them, because
access is tight. Make sure the crows
foot is perpendicular to the axis of the torque wrench, or you will get the wrong torque
on the bolts. Bee Jay decided not to reinstall the brake shroud. Instead, we put two hardened washers, about 1.7mm
(.067 in) thick, between the caliper and the mounting lugs on the trailing arm. This ensured the brake rotor was centered in the
caliper. If you are using 914-6 rotors, be
aware they are slightly larger than 914-4 rotors. The
914-6 rotors are both thicker (15mm vice 9.5mm) and greater in diameter (286mm vice
282mm). Ensure the rotor is centered between
the inner and outer halves of the caliper. If
it isnt, use a spacer between the rotor and the hub, or a hardened washer of the
appropriate thickness between the caliper and its mounting lugs. It may even be necessary to have the caliper
mounting surface milled slightly by a competent machine shop. Check to see that the perimeter of the 914-6 rotor
doesnt drag on the caliper. We
didnt have a problem, but if you do, have the diameter of the rotor machined down by
26. Secure the
brake line to its bracket on the trailing arm by reinstalling the clip.
27. Install the
dust shroud. Torque the bolts to 18 ft-lb. If you havent figured this out yet, I
recommend a drop of blue Loctite on the bolts.
No, Loctite isnt my sponsor, I just believe in their products. Also, their first factory was in my home town in
Connecticut, so using Loctite keeps my old friends and neighbors employed.
28. Install the
brake pads and retaining pins, but NOT the centering spring. Set the venting clearance to .008 inches, inboard
and outboard. You will need a 4mm hex wrench
and a clean feeler gauge. Tighten the lock
nut on the outboard adjuster, and install the plugs covering the adjusters. Remove the retainer pins and install the centering
spring, then re-install the retainer pins and their clips.
the hand brake cable.
30. Put a dab of
anti-seize on the lug studs, then mount those lovely five-lug wheels. Torque the lug nuts
to about 40 ft-lb.
31. Lower the
car to the ground, and set the parking brake.
32. Torque the
lug nuts to 94 ft-lb. I recommend tightening
in several increments, like 70, 85, and 94 ft-lb. Go
in a circular pattern, skipping every other nut until everything is at final torque.
33. Torque the axle castle nut to 217-253 ft-lb. Shoot for the middle of the torque band, 235
ft-lb. Put a socket and sturdy flex handle
over the nut, with the flex handle to the right of the nut, parallel to the ground (see photo 18). You now
need to do some simple math. Divide 235 by
your weight; the quotient tells how far from the nut you must stand on the flex handle. Example: Bee
Jay weighs 200 lb. Dividing 235 ft-lb by 200
lb gives 1.175 ft, or 14.1 inches. So, Bee
Jay centered his foot 14 inches from the nut, stood on the flex handle, and torqued the
nut to the correct value. Look at photo 19 and photo 20 to see how gracefully
he did it just like Barishnikov. This
method is much more accurate than a pneumatic impact wrench, much cheaper, and much
34. Install the
cotter key in the castle nut. You may have to
slightly tighten or loosen the nut to get key to fit through the slots in the nut. This is why we torqued to the middle of the
Bee Jay grinned at his classy new wheels, then decided he needs to
convert the front hubs to the five-lug pattern, ASAP.
With those stereo amplifiers and CD changer in his trunk, he barely has room
for one spare tire, let alone two.