SAE J2807-Performance Requirements for Tow-Vehicle Ratings

SAE J2807 is a standardized guideline that defines how Gross Combination Weight Rating (GCWR) and Trailer Weight Rating (TWR) should be determined for passenger vehicles, SUVs, and light-duty trucks. The standard ensures a consistent, objective, and fair comparison of towing capacities among different manufacturers.

1. Purpose and Scope

Establishes minimum performance criteria for vehicles towing trailers.
Standardizes test procedures to ensure comparable results.
Applies to vehicles up to 13,000 lbs GVWR (Gross Vehicle Weight Rating).

2. Test Criteria for Tow-Vehicle Ratings

2.1 Acceleration Requirements

J2807 sets specific time limits for vehicles towing their maximum rated load. Testing is conducted on a level road using the following equations:

Key Equations for Acceleration Testing

Power-to-Weight Ratio:

HP = engine horsepower
GCWR = Gross Combination Weight Rating (tow vehicle + trailer)
Acceleration Times (Modified SAE J1491 Method):
- 0-60 mph (0-96.6 km/h)
  - ≤ 30 sec (Single Rear Wheel)
  - ≤ 35 sec (Dual Rear Wheel)
- 0-30 mph (0-48.3 km/h) Interval:
  - ≤ 12 sec (Single Rear Wheel)
  - ≤ 14 sec (Dual Rear Wheel)
- 40-60 mph (64.4-96.6 km/h) Interval:
  - ≤ 18 sec (Single Rear Wheel)
  - ≤ 21 sec (Dual Rear Wheel)

2.2 Gradeability Testing (Hill Climb Performance)

Vehicles must be capable of launching from a stop on a 12% incline both forward and in reverse.
The minimum speed must be maintained while towing on the Davis Dam Grade.

Key Equations for Gradeability

Adjusted Gross Combination Weight for Test Grades

Adjusted Gross Combination Weight for Test Grades Equations

testgradetestgrade is the percentage of the test incline.
Power Requirement to Maintain Speed on Grade

Power Requirement to Maintain Speed on Grade

g = acceleration due to gravity (32.2 ft/s² or 9.81 m/s²)
θ = incline angle of the grade
Rolling-resistance is determined based on tire and road characteristics.

2.3 Highway Gradeability (Davis Dam Test)

Vehicles must maintain a minimum speed of 40 mph (single rear wheel) or 35 mph (dual rear wheel) while climbing the Davis Dam Grade at 100°F ambient temperature, with the air conditioning running.

2.4 Handling & Stability Requirements

Vehicles must demonstrate understeer characteristics when towing.
A weight-distributing hitch should restore front axle load (FALR) adequately to maintain control.

Key Equations for Handling and Understeer

Front Axle Load Restoration (FALR)

Where:

WfUT−V = Front axle weight of the uncoupled tow vehicle
WfCT−V = Front axle weight of the coupled tow vehicle (no weight distribution)
WfCT−Vwd= Front axle weight of the coupled tow vehicle with weight distribution

Understeer Requirement:

δ = Steering angle
A_y = Lateral acceleration

2.5 Braking Requirements

Vehicles towing a fully loaded trailer must stop within the defined distance in both normal and emergency braking conditions.
Trailer brakes are required for any trailer over 3,000 lbs GVWR.

Key Equations for Braking

Braking Force Calculation:

Braking Force Calculation

μ = coefficient of friction between the tires and road
W = weight of the vehicle and trailer
Stopping Distance Estimation:

d = stopping distance
V = initial velocity
μ = friction coefficient
g = gravity

3. Standard Trailer Specifications

To ensure consistency in testing, SAE J2807 defines standard trailers based on weight, size, and configuration.

Key Trailer Characteristics

Standard Axle Configurations: Single or Tandem
Maximum Effective Tongue Lengths: Ranges from 83 inches to 420 inches
Minimum Frontal Area Requirements: Ranges from 12 ft² to 75 ft²

4. Tow-Vehicle Structural Requirements

Ensures hitch receivers, frames, and attachment structures meet SAE J684 and SAE J2638 standards.
Establishes durability and deformation limits for weight-carrying hitches, weight-distributing hitches, fifth-wheel, and gooseneck towing.

Key Equation for Structural Strength

Angular Deformation Limit for Hitch Attachments: θ_max = 5^∘ where:
- θ_max = Maximum permanent deformation angle.

5. Industry Impact and Adoption

SAE J2807 ensures accurate, comparable, and realistic towing capacities.
Major automakers (GM, Ford, Toyota, etc.) have adopted the standard for towing ratings.
Consumers benefit from safer towing experiences and more transparent vehicle specifications.

Conclusion

SAE J2807 is a critical towing standard that enhances safety, consistency, and transparency in vehicle ratings. By establishing objective testing criteria for acceleration, braking, handling, and structural integrity, it allows consumers to make informed decisions when choosing a vehicle for towing.

SAE J2807-Performance Requirements for Tow-Vehicle Ratings

1. Purpose and Scope