Toyota Landcruiser Rear Brake Upgrade Package

May 2007
Toyota Landcruiser
Rear Brake Upgrade
Package
HOPPERS STOPPERS
9 Nevada Ct
Hoppers Crossing Vic 3029
Ph 03 97486950
Fax 03 97485965
Email [email protected]
Web www.hoppers.com.au
Toyota Landcruiser Rear Brake Upgrade Package
THE INFORMATION CONTAINED
WITHIN THIS DOCUMENT IS
PROPRIETY CONFIDENTIAL
AND MUST NOT BE DIVULGED
TO ANY THIRD PARTY WITHOUT
OUR WRITTEN CONSENT
HOPPERS STOPPERS
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Toyota Landcruiser Rear Brake Upgrade Package
Rear Brake
Upgrade
Package
78/79 Series
Toyota
Landcruiser
Introduction
Toyota Landcruiser 78/79 Series Vehicles are used extensively
throughout the country, and in particular, are favoured by mining
operators, many in underground use where conditions are
extreme.
Whilst the basic vehicle is well respected by the industry, the rear
disc brake arrangement has proven to be inadequate for the
conditions, with the rear brake pads and hand brake both
exhibiting accelerated wear way beyond the rest of the vehicle.
In worst conditions, the rear brake linings will wear to the metal
backing plates in a matter of weeks, resulting in total loss of rear
brakes with accompanying work safety concerns. Handbrakes
often fail to hold with days.
Analysis of the Problem
With this series of 78/79 series vehicles, Toyota moved to a rear
disc brake design incorporating a drum type hand brake within the
disc.
Original rear slip-on disc with small
caliper
Handbrake inside rear disc
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There may have been reasons for this design, but it seems to
have been a retrograde step when subjected to regular immersion
in muddy and highly corrosive environments.
There seem to have been several compromises needed to arrive
at this design.
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Toyota Landcruiser Rear Brake Upgrade Package
Cause of Rear Brake Problems
1
Combining a drum handbrake and a disc rotor and caliper
within the confines of a 16-inch wheel necessitates a
small brake caliper and small pad radial section, resulting
in an undersized pad area.
The standard design has a thin disc and a handbrake of
small diameter and swept area relative to the weight of
the vehicle.
2
The backing plate and handbrake arrangement allow mud
and slurry to enter but not exit, causing abrasives to
accumulate and rapidly destroy the handbrake, including
its function as an emergency brake.
3
The small disc pad contact area is at odds with the
affects of loading under abrasive conditions where rates
of wear are parabolic for wear rate versus load.
4
The handbrake design is fiddly and complicated with
many small parts that prove to be difficult to assemble
correctly.
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Rear Brake
Upgrade
Package
78/79 Series
Toyota
Landcruiser
Hoppers Stoppers design solution
There appear to be a few possible ways to approach this
problem, with a couple of companies proposing designs.
Some take unconventional and unusual approaches but appear
expensive to purchase and repair; with their application probably
only justified if they perform perfectly for a very long time.
Hoppers Stoppers' approach is to stick to proven principles and
overcome the basic weakness of the existing design.
300 dia by 28 thick rotor fitted to
original hub
By all reports, the front brakes on these Toyotas work adequately,
and considering their environment do not give significant
problems in the field.
In our view these brakes are not particularly special in their
engineering, just the same basic front brakes that they have
made for many years.
If we built a rear brake set as solid and even better designed than
the front it should last as long. This requires a big, thick disc rotor
and brake lining swept area similar to the front.
Larger revised caliper
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Toyota Landcruiser Rear Brake Upgrade Package
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Improved Design By Hoppers Stoppers Handbrake
Relocation
In order to provide a suitably robust rear caliper and rotor design,
it is therefore necessary to go back to the 'old days' and relocate
the park brake back to the rear of the gearbox transfer case.
Rear view of transfer case
As drum brakes accumulate abrasives, it is best to do this with a
disc brake design, the disc being attached to the output flange
and the caliper of simple mechanical lever type attached to the
end of the transfer case.
This allows us to utilize the differential ratio to "multiply" the brake
effect for an effective park/emergency brake, which is also better
located up higher for less emersion in mud.
Disc type handbrake installed
1 Rotors
Being a full floating rear hub and axle design, restricts the
inside diameter of the rotor face, particularly when we try to
retain the simple loose fit "slip on" design.
In order to achieve a suitably larger swept area, it is therefore
better to attach the rotor from the inside in the same manner as
the front arrangement.
This will require the hub to be removed from the axle housing
for disc fitment; this is not a big job and in any case allows
repacking of the bearings.
In order to facilitate the original conversion, 5 counter sunk
holes need to be drilled on the rear carrier hubs, either at the
mine's workshop or as a change over supplied by Hoppers
Stoppers.
The end result is a 300mm diameter rotor; 28mm thick
compared to the original 18mm thick and almost double the
swept area.
No other alterations are required and all standard bearings and
seals are retained, with the ability to convert back to the
original design if desired, say at time of trading in the vehicle.
HOPPERS STOPPERS
Hoppers
Stoppers
Rear Brake
Design
78/79 Series
Toyota
Landcruiser
Toyota Landcruiser Rear Brake Upgrade Package
6
2 Caliper Design
Within the automotive industry, all common rear calipers are
much smaller than the front with usually much smaller pad
area.
Brake balance considerations dictate much smaller rear
hydraulic piston areas, essentially meaning that there is no
readily available alternative rear caliper that offers a solution.
We therefore achieve our desired large pad area and thick
rotor requirements by sleeving an Australian made front caliper
down to smaller bore piston of suitable diameter.
Handbrake caliper, mounting
bracket, disc rotor and carrier
plate
This also has an added benefit of allowing us to make the
sleeves and pistons from corrosion resistant materials more
suitable for the intended use.
These calipers are plated cast iron, and by specification
designed for regular immersion in dirt and water.
3 Brake Pads
As the base calipers are originally for the front of a locally
made vehicle, the pads are available in many material options.
Brake torque applied by a caliper to a rotor is proportional to
the hydraulic area and does not change with pad area.
It is therefore possible to reduce the specific load on the pad,
greatly reduce wear rate and still have correct brake torque.
4 Attachment
Caliper mounting to the axle housing is via a 12mm thick steel
plate attached to the original backing plate holes using original
size 4 off 12mm bolts.
For comparison, the original caliper attaches to a 5mm plate.
The new caliper cradle attaches to this using 2 off 12mm bolts,
which are the same size as original Toyota rear caliper usage.
Rear Brake Kit ready for installation
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Hoppers
Stoppers
Rear Brake
Design
78/79 Series
Toyota
Landcruiser
Toyota Landcruiser Rear Brake Upgrade Package
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5 Handbrake
To attach a suitable "tail shaft disc" we arrange a 10mm thick
carrier plate to be sandwiched between the output flange and
the universal joint yolk.
This requires a small and acceptable movement of the slip joint
at the front of the tail shaft.
Before
This caliper is designed for regular immersion in saltwater with
all metal parts being either hot zinc coated or stainless steel.
It is attached to the extension housing using six bolts already
used to attach the end cover plate.
The original hand brake cable is rerouted from its position on
the left hand side of the axle to the chassis at the centre of the
vehicle where it will work the centre-mounted handbrake.
Note that we have avoided hydraulic actuation of the park
brake as any brake fluid leaks would cause the brakes to
release, as would any cooling of the hydraulics.
Eg. After parking the vehicle with the brakes in a hot state.
After
Summary
Hoppers Stoppers rear brake upgrade design principle is based
on the fact that known acceptable front brake performance is
repeatable at the rear.
The basic vehicle remains unmodified in every aspect with
existing brake master cylinder and piping, wheels, hubs, gearbox
and such kept in standard condition.
Handbrake
Fitting is simple and quick with normal tools and no special
knowledge.
Initial kits are not expensive and spare parts similar to that
currently paid.
The product is provided with an Engineers Report suitable for
legal registration so that road going units can be converted and
when sold, the new owner can legally continue to use the vehicle.
From Inside
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Toyota Landcruiser Rear Brake Upgrade Package
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Toyota Landcruiser Rear Brake Upgrade Package
HOPPERS STOPPERS
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