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Airstream Life Article on Kodiak Disc Brakes |
Airstream Life Article on Kodiak Disc Brakes
Electric drum brake technology has been virtually
unchanged for decades. The electric
drum brakes that are most likely in your
Airstream right now are direct descendants
of the drum brake first invented in 1902 by
Louis Renault.
Electric drum brakes are still predominant
on travel trailers, but they aren’t nearly
as effective as disc brakes. Moisture can
cause them to grab, or slip, depending on
how damp they get. Braking action fades
due to heat generated during braking results
in reduced braking, especially under hard
stops. Because drums can’t dissipate heat
effectively, this effect rapidly increases with
time, which the driver feels as a loss of braking
power, or fade. This can happen in a
fraction of a second under hard stopping
conditions.
Unfortunately, heat also decreases the
effectiveness of the electromagnets as well,
which causes a “double whammy” effect.
Less-effective magnets means the driver
must step on the brake pedal harder to get
the same response.
Compounding the problem is the fact
that modern tow vehicles have disc brakes
which are virtually immune to fade, as well
as being far more aggressive in their braking
capacity. In hard stopping situations, the
trailer brake fading results in an increasing
transfer of inertia to the tow vehicle. Tow
vehicle braking systems are not designed to
stop more than the maximum weight (GVWR)
of the tow vehicle, so the result is vastly
extended braking distance at exactly the
wrong moment. In short, trailers with drum
brakes (especially heavy trailers) are mismatched
with a tow vehicle that has disc
brakes.
As trailers have become heavier and
larger, disc brakes have been a logical evolution,
but the old-fashioned drum brake that
one can find on any vintage Airstream has
remained the staple of the RV industry. A primary
reason is cost: electric drum brakes
are cheaper.
Airstream offered a hydraulic disc
brake system in the 1980s, but due to complexity
of the vacuum-powered actuating
system, they discontinued the option after
only a few years. As technology advanced
over the last couple of years, the complexity
of proportionally-actuated disc brakes on
the trailer has became manageable, less
costly and more reliable, so starting with the
2005 Classic models, Airstream has begun to
offer disc brakes again.
Kodiak, the manufacturer of the disc
brakes used by Airstream, claims their disc
brake system offers smoother and shorter
stops, which was borne out by our experience
(see sidebar). This is due to the lack of
fading as well as vastly superior braking
capacity of discs compared to drums. With
the Kodiak system, the brakes can stop 8,000
pounds per axle, so in a tandem axle, you
have 16,000 pounds of stopping capacity – or
better than 50% more stopping power than
the heaviest tandem axle Airstream with
drums. That can easily be the difference in a
controlled hard stop and a white-knuckle
experience or worse.
Deciding To Upgrade
Since the overwhelming majority of
Airstreams on the road today have electric
drum brakes, an upgrade package is available
and can be installed by the factory ser ice center in Jackson Center OH, as well as
some Airstream dealers. The upgrade can
be done to any Airstream, including vintage
trailers of any size.
One common question is whether the
resulting disc brake system is serviceable at
any brake shop. It is, and all of the necessary
replacement parts are readily available at
auto parts stores. The Kodiak system uses a
standard General Motors brake pad, and
brake technicians will find no surprises
when working on the Kodiak disc brakes.
However, the Kodiak brake system uses
a slightly different rear (inner) wheel bearing
as compared to the Airstream electric drum
brake system. This bearing is a higher
capacity bearing, and the two bearings cannot
be interchanged. While they may appear
the same, they are not and installing the
wrong bearing will result in bearing failure.
This applies to retrofitted rigs as well as factory
equipped units.
Another question stems from the
instructions printed in the Tekonsha Prodigy
brake controller owner’s manual. That manual
states that the popular Prodigy unit is not
tested for disc brake systems. Active
Technology, maker of the ActiBrake disc
brake actuator used in the Airstreaminstalled
system, states that their system has
been tested and is compatible with Prodigy
as well as a number of other proportional
brake controllers. However, the ActiBrake
cannot be used with time-based brake controllers.
(For more information, see the
Active Technology website and download
their Owner’s Manual and Installation
Instructions.)
An interesting benefit of the Active
Technology / Kodiak hydraulic disc brake
system is that it can be used as a temporary
parking brake while hitching and unhitching.
While electric drum brake users are warned
not to pull the emergency break-away cable
for more than a few seconds, (lest the electromagnets
burn out) the disc brake system
doesn’t have that limitation. The ActiBrake
unit has an “Extend-A-Hold” feature which
can keep the brake lines pressurized indefinitely
without constantly running the actuator
pump. After a short period of constant
operation of the pump, the pressure in the
line is locked and the pump shuts off. Every
30 seconds, the pump fires back up to
ensure constant pressure on the lines. This
feature also comes into play during prolonged
stopping and ensures that the brake
fluid is not overheated in the pump. Any
change in the electrical signal to the actuator
releases the “Extend-A-Hold” feature
instantly.
When the break-away cable pulled, the
trailer is locked in place, with all disc brakes
fully engaged. However, the pump draws a
lot of DC power whenever the pump is running
(up to 21 amps). That will drain a trailer
battery if accidentally left on while parked
and not connected to shore power, so this
feature should be used during hitching and
unhitching only. It can and should also be
used when changing a flat tire as a precaution
against the trailer rolling. Additionally,
this practice checks the emergency breakaway
switch whose operation is seldom verified
otherwise.
While upgrading to disc brakes is not
cheap, they are becoming popular with
Airstreamers. Whether for safety, convenience,
or improved performance, it is an
upgrade that is likely to become even more
popular in the future.
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Disc Brakes
