The Supreme Corporation submitted a model PS-31, diesel powered 27 seat/31-foot bus, for a 7 yr/ 200,000 mile STURAA test.  The odometer reading at the time of delivery was 0,518.0 miles.  Testing started on February 11, 1998, and was completed on May 11, 1998.  The Check-In section of the report provides a description of the bus and specifies its major components.

The primary part of the test program is the Structural Durability Test, which also provides the information for the Maintainability and Reliability results.  Structural Durability Testing was started on February 12, 1998 and was completed on April 8, 1998.

The first segment of the Structural Durability Test was performed with the bus loaded to a GVW of 19,580 lb.  The number of standing passengers was reduced from 15 standees to 0 and 5 rear seated passengers were eliminated.  A reduction in passenger weight was necessary to avoid exceeding the GAWR (12,000 lbs.) of the rear axle.  The middle segment was performed at a SLW of 19,580 lb. (Note: 5 rear seated passengers eliminated to avoid exceeding GAWR of the rear axl).  The final segment was performed at a curb weight of 7,390 lb.  Durability driving resulted in unscheduled maintenance that consisted of a variety of subsystem failures.  These unscheduled maintenance breakdowns can be found in a complete and detailed listing of scheduled and unscheduled maintenance, which is provided in the Maintainability section of this report.

Accessibility, in general, was adequate, components covered in Section 1.3 (Repair and/or Replacement of Selected Subsystems) were found to be readily accessible and no restrictions were noted.  The only notable access problem encountered during testing was with the engine coolant drain.          

The Reliability Section compiles failures that occurred during Structural Durability Testing.  Breakdowns are classified according to subsystems.  The data in this section is arranged so that those subsystems with more frequent problems are apparent.  Failures are classified according to the severity as defined in Section 2.  The test bus encountered No Class 1 or Class 2 failures.  Of the twenty-seven reported failures, eleven were Class 3 and sixteen were Class 4.

The Safety Test, a double-lane change (obstacle avoidance) Test was safely performed in both right-hand and left-hand directions up to a maximum test speed of 45 mph.  The performance of the bus is illustrated by a speed vs. time plot.  Acceleration and Gradeability Test data are provided in Section 4, Performance.  The average time to obtain 50 mph was 23.81 seconds.

The Shakedown Test produced a maximum final loaded deflection of 0.256 inches with a permanent set ranging between -0.003 to 0.005 inches under a distributed static load of 16,350 lb.  The Distortion Test was completed with water leakage observed during the test at the top rear corner of the last window, curb side.  All subsystems operated properly.  The test bus was not equipped with any type of tow eyes or tow hooks; therefore, the Static Towing Test was not performed.  The Dynamic Towing Test was performed by means of a front lift tow.  Due to the lack of tow eyes or tow hooks, the towing interface was accomplished by chaining to the front axle.  The manufacturer does not recommend rear towing.  No deformation or damage was noted, and no problems were encountered with the towing interface.  The Jacking and Hoisting Tests were also performed without incident. The bus was found to be stable on the jack stands, and the minimum jacking clearance observed with a tire deflated was 4.20 inches.

A Fuel Economy Test was run on simulated central business district, arterial, and commuter courses.  The results were 6.09 mpg, 6.73 mpg, and 12.57 mpg respectively; with an overall average of 7.38 mpg.

 A series of Interior and Exterior Noise Tests was performed.  These data are listed in section 7.1 and 7.2 respectively.


Number: 9801
Model: PS-31
Vin Number: 4UZABFADXVC934798