OFF CAMBER PRODUCTIONS
Background
The design of the braking system on Toyota pickup trucks from 1979-1995 have drum brakes on the rear axle. These trucks are very popular off-road vehicles and the rear brakes lack the stopping power in which many desire. When these trucks are used off-road the drums tend to fill with mud which can dangerously decrease the braking efficiency of the truck.
Currently there are brackets on the market which adapt disk brakes to the rear, but none of the aftermarket solutions incorporate a caliper that ties into the factory emergency brake system. Most manufactures of these brackets advocate adding a transfer case emergency brake which can be more expensive than the disk brake conversion itself. From many reviews this much smaller emergency brake does not withstand the weight of the vehicle and
allows the vehicle to roll even when the emergency brake is applied.
The aftermarket industry plays off of the philosophy that bigger must be better. Many of the companies claim that their 3/8” thick steel plate is the only way to go and that anything that is smaller in design is inherently weaker. In an engineering sense why add unnecessary weight or bulk when it is not needed? For the brackets that are being designed different materials will be viewed to see if another material such as aluminum which is lighter than steel can hold up to the abuse. Many of the aftermarket hot-rod disk brake conversions employ aluminum in their bracket design where high speed braking is the norm.
If these hot-rod manufactures can use aluminum in their design, then there is no reason aluminum or another type of material can be used on an off-road application.
The Analysis:
After landing a design that was desired to incorperate the Ford Mustang Calipers and Mitsubishi Montero rotors a material needed to be selected. Two variations of material were chosen, one was to be 6061-T6 Aluminum and the other would be A-36 steel.
The scenario for the design of these brackets was based on the 4000 lb. test truck traveling at 40 miles per hour and coming to a stop in 75ft.
With the material selected and the size and shape defined, the variable of thickness could be calculated. After working through the dynamics involved with braking and the moment arm placed on the bracket when the brakes are applied, the stress within the bracket could be calculated. from this stress analysis the thickness of the material required could be deduced. As a final result the thinest possible brackets for the 1986 toyota test vehicle were .080" made out of aluminum and .1046" in the A-36 variety.
With this in mind, the thicknesses that were derived were specifically for the test vehicle that is being used. If the truck were to weigh more or travel at a faster speed pior to braking then the bracket thickness must be thicker. This is where phase II of the project comes in to play!
Phase II designs were based on the scenario of a 5000 lb test vehicle coming to a stop in 75 ft from 50 miles per hour. After working through the braking dynamics and the static moment arm that is placed on the brackets mounting location the new corresponding thickness was deduced. both the 6061-T6 aluminum and the A-36 steel required a thickness of .25"
Results
Currently the truck is in the testing phase of the build process. The 1986 Toyota pickup test truck has been fitted with the disk brake conversion and has gone through the initial shake down test over rough terrain to ensure that the tolerances were proper and that nothing would interfere. The initial set up is using the .25" thick steel bracket to ensure that the brakes are properly set up prior to installing the minimum thickness brackets for testing.
Follow the link below for the full test data!
Brackets that won't break the budget!
Toyota pickup trucks from the 1980's and 1990's are very popular in the offroad community and due to the sheer quantity of Toyota's still on the road today a better braking solution for the rear of the vehicle is in high demand!