Curbstone Clearance, Approach, Departure, and Ramp Breakover Angles—Passenger Car and Light Truck(Cancelled Aug 2009)
This SAE Recommended Practice applies to rigid bumper or rigid structure points and flexible components of passenger cars, multipurpose passenger vehicles, and light trucks. This document is intended as a guide toward standard practice and is subject to change to keep pace with experience and technical advances.
This Recommended Practice provides minimum static design guidelines for curbstone clearance, approach, departure, and ramp breakover angles at a manufacturer’s most severe vehicle design load. This is to minimize the potential for any damage in normal vehicle use conditions. SAE J689 also defines front and rear bumper heights for two different vehicle loading conditions, but does not provide any design guidance.
The document was last revised in 1996 by the Bumper Standards committee (no longer active). It was confirmed that all dimensions save “3.8 Parking Curbstone Height Clearance” are in the current SAE J1100 with illustrations. Curbstone heights are typically a function of road classification (source: AASHTO). HADD agreed to adopt SAE J689, incorporating curbstone definition into SAE J1100, then to CANCEL it once SAE J1100 was published.
The dimension minimum values given in SAE J689 are:
These target dimensions in SAE J689 will be lost, but the HADD committee determined that these values were not very useful for current vehicle designs. Manufacturers typically establish design minimums that differ according to vehicle type or market segment. A single minimum value that applies to all vehicles (such as provided in SAE J689) for curbstone clearance, approach, departure, and ramp breakover angles is no longer sufficient.
The following table maps the SAE J689 dimension codes to their SAE J1100 equivalents: