Brakes/Axles
I learned how to replace
& adjust brake shoes, and repack bearings on a 1968 Volkswagen when I was
15 years old. Although I enjoyed the
task, it was done out of necessity for my dad since he is not a hands-on type,
and the last VW mechanic had left town.
Working as a mechanic for a while after high school gave me insight into
the brakes, wheel bearings, and suspension systems on a variety of conveyances.
In general, I consider it
good practice to repack wheel bearings whenever new shoes or pads are
installed. A time-based schedule is of
little value because nothing in the hub goes bad in this relatively short
amount of time. The grease is protected
from outside contamination by the dust cap & the grease seal. If you do all your own maintenance, you are
typically using the same can of grease you used last time, and the grease is
basically thousands of years old anyway if you think about it. On most spindles, there is only one correct
setting for bearing preload, so unless the bearing self destructs, there is
nothing to check there.
Pulling the hub &
inspecting the brakes is a good idea, but there again mileage drives how much
wear there will be. If you are out there
adjusting the brakes on a regular basis & keeping track of your mileage,
you will already know when brake work is due & what to expect. If you are new to packing bearings, and
replacing & adjusting brakes, you would do best to pull the hubs once a
year if you do not reach the 10,000 mile mark just to build an experience base. If it is simply that Airstreams are new to
you, everything on the spindle is just like what you have already seen.
While prepping my Overlander to be towed for the
first time in 23 years, I had every intention of repacking the wheel bearings
before leaving the previous owner’s driveway.
Pulling the first hub, the grease looked so good I could have declared
it had just been repacked. While I knew
at face value that was a remote possibility, I confirmed it by examining a dab
of the grease – It was that “stringy” type I used to buy in the mid seventies
for drum brake hubs, and it has not been commonly available for years. Since all four wheels passed the “wiggle test”
(bearings were good), I elected to leave the bearings alone until I had the
Airstream back at my shop.
The brake shoes had more
than enough lining left but the brake magnet (shown at left) was suspect. While I knew the theory of how electric
brakes worked, an opportunity to work on them had never presented itself. Common sense told me that screw heads should
not be worn away, but since these particular three were made of brass (which
would not scratch the armature plate (magnet pad)), I decided they were
adequate for the 70 mile trip home.
While I have towed one thing
or another all my life, the Airstream was not the heaviest thing my Suburban
has ever pulled. The heaviest load was
around four tons of brick, and the ‘Burb pulled it, and stopped it without
electric brakes, across three states. So
for a leisurely Saturday afternoon drive home, I really wasn’t too concerned
about how well the electric brakes worked.
Although the brakes did work, I pulled over several times to check for
loose wheels, and to make sure the new tires I had installed were not running unusually
warm. The trip home was without
incident.
Once safely
home in my own shop, I had more time to study the brakes’ condition. Interesting.
All eight shoes still had lots of life left, but the magnets were all
shot. This was disappointing in that the
previous owner had always had an out of town Airstream dealership do all this
type of work. I can only speculate as to
why the magnets were worn much more than the shoes. But this discrepancy made me wonder if the
three broken, lower return springs found has broken after the last service
trip, or were just installed broken. I
was also disappointed to find that the grease seals had obviously been reused
several times.
The task of replacing one boogered-up lug
stud proved to be more challenge than I was anticipating. For starters, the magnet plate covered the
stud’s head, and the plate was riveted on.
Drilling out the rivets allowed one ordinary looking stud to be pressed
out. FWIW, nowadays, electric brake
drums are of a one-piece construction.
In what was no
great surprise, the standard trailer lug stud has changed. While my stud still had a standard ½-20
thread, the splined, or knurled diameter had everyone pulling out the
old paper catalogs. A chain store called
O'Reilly's was finally able to sell me a stud with my 0.612" knurl
diameter. I still had to do some minor
machining, however, to make it fit my application.
Grade 8, ¼-20,
flush head fasteners were used to re-secure the magnet plate.
Apparently, nowadays, most
people service their brakes with a loaded
backing plate instead of purchasing shoes & magnets individually. It may be cheaper; I don’t know.
But I did have a knowledgeable parts man tell me once that the loaded
backing plates he sold would not work with my Kelsey-Hayes drums. The shoes, magnets, etc. themselves would
work okay, but there is apparently some interference between the drum & the
backing plate. I plan to look into this
option more when the next brake maintenance occurs. If its cheaper, I will do it. But I don’t mind detaching & attaching
return springs, and to me that task appears easier than R&Ring
the backing plates’ nuts & bolts.
Judging by the condition of
the shock absorber grommets, I was willing to bet that I was looking at the
original shocks. Made by Delco, the
shocks had the following wording, “4975425 PLIACELL 136 72 DELCO PRODUCTS DAYTON OHIO USA”. I replaced
them with shocks from an Airstream dealer (probably made by Gabriel). Of note here, I bent the upper shock bracket
a bit to replace the shocks since dropping the axles would have been the only
other way to accomplish the task. . Looking at both the geometry of the mounts,
and the shocks’ degrees of freedom, I could have left the bracket bent, and the
shock would have still done its job. But
I bent it back.
The Overlander was now ready
for the road.
You know what they say about opinions…
Up to this point, everything
you have read could have applied to any trailer with electric brakes. This also concludes the discussion of all the
actual work I have done on my Overlander’s running gear. The text that follows should be taken as just
another opinion from the Internet, and unlike the rest of my site, is not open
to discussion. “I yam what I yam”.
While I have not made any
unsafe repairs to the axles or brakes, what I have not done as well as the way I approach a given situation runs
counter to popular sentiment. I
subscribe to the theory that I am responsible for my own safety both in the way
I tow, and maintaining all my gear on a routine basis. While you have a responsibility to keep loose
banana peels off your front step, I have a responsibility to watch where I am
going should you want me to ring your doorbell.
I have been subjected to way too many non-thinking individuals under the
impression that just because something is either old or of old technology it
should be replaced. I have also grown
weary of dealers & vendors presenting accelerated service intervals in the
name of safety while asking me to forego common sense.
Disk Brakes
The current rage
in brakes, if you hang around Airstreamforums.com, is to retrofit disk brakes
in place of the drum brakes. At face
value, there is nothing wrong with the modification. If one looks a little deeper into the issue,
there will still be nothing wrong
with doing it, but if all aspects are considered, one may not be better off in
spite of spending a rather large sum of money.
Now, I will allow that I am
not the best candidate for this upgrade.
My primary tow vehicle is a 1984 Suburban C20. In 1984, that meant you got a heavy truck
with a true ¾ ton suspension and brakes.
As mentioned earlier, the truck was quite capable of stopping itself
plus 8000 pounds of brick in a reasonable distance. My secondary, ¾ ton tow vehicle, while not as
stout as the first, has the same tow ratings.
Now, the only reason one should want disk brakes is their
resistance to fade. Any friction brake’s
stopping force, whether it be disk or drum, diminishes as it heats up. The general, open design of a disk brake both
keeps this heat from building up as fast, and lets it dissipate faster. So, with improved brakes, you would be able
to zip down a mountain or speed through a school zone faster than you did
before. But if you think you had instances
of brake fade with your old drum brakes, I would submit that you may not have
adjusted your driving habits appropriately when towing a trailer.
But vendors are hawking
another selling point: Ease of pad
change, “No more pulling the drum off to check the shoes”. Sounds good, but Airstream still recommends
repacking the bearings every year or 10,000 miles, so the rotor & caliper
is coming off anyway resulting in the same level of maintenance effort.
Single point failure: Disk brakes pads are actuated from a
hydraulic pump, a feature that drum brakes do not require. If this pump quits, you have no brakes. The hydraulic fluid is brake fluid, and most
Manufacturers recommend brake fluid be changed every two years. I do not know what the recommended interval
is for this retrofit application.
Then there’s the
installation. I have not read the
recommended procedure, but I do know that one vendor wants the hydraulic pump
to be mounted inside somewhere. So, one
needs to plan on giving up some floor space for the effort. Chances are that the belly skin will need to
be dropped to run the electrical & hydraulic lines. While not particularly difficult, it can be
time consuming. If a shop does this work
for you, the hours can add up.
Keep in mind that my intent
is not to talk anyone out of using disk brakes on their trailer. My goal is for people to understand the
encumbrances associated with disk brakes, and to stop & think if their
towing habits & towing setup would benefit from the installation. If you decide disk brakes are for you, and
live around here, call me, and I will help you install them. I am comfortable with my setup, and I would
like everyone else to be comfortable with theirs.
Axles
What sets an Airstream apart
from just any old trailer is their use of Henschen’s Dura Torque axle. A
fine piece of engineering, you can read more about it at this vendor’s site. If I had never visited Airstreamforums.com,
it is doubtful that I would have ever given much thought to my axles. But I did, and in spite of vendor pleas, I
have not replaced my axles..yet. I need to both
convince myself that new axles would benefit my Overlander, and that I will be
camping enough to justify the cost. New
axles don’t do a thing for an Airstream that never moves, and I doubt I would
recover my costs if I were to sell my pride & joy. So far, while we are camping enough to justify
the cost, axles have been relegated to the Another
opinion from the Internet section of my site because I have several
observations & opinions about when to replace axles which are unpopular
with the axle vendors.
I have no qualms about
replacing axles based on camber angle. Take
another look at the picture at the top of this page. Notice the amount of tire showing between the
top of the rim, and the bottom of the fender well? I knew before I climbed underneath that I
still had good camber angle. But the
vendor’s site infers that axles on pre-1974 Airstream are bad, and should be
replaced. Although possible, it could just
be a selling point since the manufacturer made a materials change in ’74. Why was the material changed? While I am sure it was for the better, what
drove the change? Based on no facts, my
SWAG is that the change was for better cold weather resistance. My Overlander has always lived in the Southeast.
Short of an accident, the
only thing that can go bad in a Henschen axle is the synthetic and natural
rubber cord material. Wear & tear on
this material manifests itself in a positive camber angle on the torsion arms. Old age, I assume, could dry out the
materials making them more stiff. “Stiff”
is somewhat subjective in this situation.
Those cords have to be really stiff to start with since each torsion arm
is supporting a cantilevered load of roughly 1500 pounds. If the material was to get too stiff, I would
think it would slowly shear as the trailer is towed down the road encountering
dips & the occasional pothole while the torsion arm barely moved. Shearing would lessen the amount of connected
material able to support the load. Shear
enough material, and the camber angle would go positive. Time to replace the axles.
So then I wondered if the
cords were just too stiff to move or
shear. My question was answered one day
while towing the Airstream down a sectioned-concrete road. This is the type of road where you can hear
the tow vehicle’s tire rhythmically “ka-kunk” across
each joint as you bob up & down in your seat every time the sound is
heard. Looking at the mirrors, the
Airstream’s suspension system could be seen accommodating the road conditions
by allowing the trailer to gently rise & fall with each passing joint. Kinda cool looking. Enough to make you seasick though if you were
riding in the Airstream.
Another argument about stiff
old axles is that they transmit road vibration into the trailer, which cracks the
frame & pops rivet heads. While that
may be a valid point, I consider it moot, as the bulk of trailer destroying
vibration, in my opinion, comes from unbalanced running gear. In this context, running gear is anything
that rotates: tires, wheels, and brake drums.
Apparently, the brake drums on both travel & utility trailers are
not balanced at the factory like most automobile drums are. While your tire shop can balance the
wheel/tire assembly, there are very few shops that can balance all the running gear simultaneously. This rotating imbalance is what does most of
the damage, and there is very little that can done about it unless your tire
shop has the right equipment. Worrying
about it, I ordered some Centramatic
Wheel Balancers to deal with the issue.
Unfortunately, this product only works with zero-offset wheels – The balancers
would not fit my Airstream. So, I just
live with unquantified vibration.
I could take a ride in my Airstream to gauge the relative vibration,
and the axles’ reaction to different road conditions, but I have no basis for
comparison as I do not know anyone with a certified “vibration-free”, new Airstream
with which I could compare the ride. I
was, however, encouraged by an incident which occurred on one camping
trip. Plans were to meet up with another
couple at a gas station about 15 miles from our house. Besides navigating out of our neighborhood,
getting to the rendezvous point required traveling down a busy four-lane under
construction at both ends. While waiting
for our friends to arrive, my wife noticed the Mr. Coffee still sitting on the
sink countertop. I was encouraged that
it had not moved.
As mentioned earlier, I have
not replaced my axles yet. But one disheartening aspect I keep in mind
is that I may not be rewarded visually for the replacement’s effort. One fellow I know replaced his axles based on
age, and a tad of positive camber. He
even purchased approved higher load-rated axles. After the installation, while he had more
rubber showing at the top of his tire, it was not that much. As I recall, it
was not even as much I currently have showing. L
Getting the new axles delivered
without damage is another concern if you plan to install them yourself. New axles, no matter who your retailer is,
are freight-shipped from Henschen strapped to a pallet. Even with conscientious forklift operators,
since the axle ends extend over the pallet, the possibility for damage is
high. If it’s a bare axle, i.e. no
backing plates & drums, damage may be easy to detect. With loaded axles, it may not be easy to tell
if the pallet was dropped. I have read
many tales of damage, and it was usually the customer who lost in the long run.
To summarize, it is not my
intent to talk anyone out of disk brakes or new axles. If, after reading my opinions &
observations above, you still think disk brakes or new axles are still the best
purchase for your Airstream, then go for it.
Hopefully, though, you have picked up some bit of information which will
help you appreciate the points that vendors do not care to discuss.