Calculate parking brake holding force on a grade based on vehicle weight, grade angle, and brake mechanical advantage.
Input Parameters
Results
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Grade Force on Vehicle
lbs
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Parking Brake Force
lbs
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Safety Factor
--
Max Holdable Grade
%
Note: FMVSS 135 requires parking brakes to hold on a 20% grade (both up and down). A safety factor of at least 1.5 is recommended.
Reference
Grade Angle = arctan(Grade% / 100)
Grade Force = Weight x sin(Grade Angle)
Brake Force = Cable Force x Mech Advantage x mu x 2
Safety Factor = Brake Force / Grade Force
Max Grade = tan(arcsin(Brake Force / Weight)) x 100