Grumman Flxible 870

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Grumman Flxible 870
Grumman Flxible - 870
Years of manufacture 1978 to 1983
Length 35 or 40 feet
Width 96 or 102 inches
Power/Fuel Diesel

The Grumman Flxible 870 was a high floor transit bus produced in the United States. In the last year of production, the 870 became known as the Grumman Metro.[1] Grumman sold Flxible to General Automotive Corporation in 1983 and production of the Metro continued under the Flxible name (see Flxible Metro).

Design history

The 870 can be seen as the final iteration of a new and innovative transit bus that Rohr, the parent company of Flxible, began working on in the early 1970s. The first bus was dubbed the "Hi Value" bus and was meant to be lightweight as well as cost effective to manufacture. Rohr was also a participant in the Urban Mass Transit Association's (UMTA) Transbus program. The goal was to design a bus that was lightweight, comfortable, and accessible to the elderly and disabled.

The Rohr Transbus had tandem front and rear axles with low profile tires. The under-45-foot-long bus had a one-step floor height of 22 inches as mandated by the UMTA to offer easier access. The bus had large, deeply tinted, flush-mounted windows and air conditioning to improve comfort. Three buses were shown off around the United States. However, the future of the Transbus project became uncertain by 1976 as concerns rose over development and production costs.

Both General Motors and Rohr announced their intention to to produce so-called "Advanced Design Buses" (ADB) in the interim. The General Motors RTS and the Grumman Flxible 870 incorporated features of the Transbus project, but would cost less and enter production sooner. The UMTA conceded that a 24-inch floor height achieved through a combination of lowered floor height and kneeling feature would be acceptable to qualify for federally funded procurements.[2]

The 870 featured contemporary angular styling. Like the Transbus design, it had large, tinted flush-mounted passenger windows. It also had a lower floor height than previous buses and was equipped with a wheelchair lift. The bus's aluminum side panels were attached with hidden fasteners.

Rohr sold Flxible in January 1978 to Grumman, which became Grumman Flxible. The 870 soon entered production and the Flxible New Look was discontinued. In September of that year, a consortium comprising of Los Angeles, Miami, and Philadelphia issued a tender under Transbus specification. However, no manufacture responded with a bid. Grumman Flxible cited the risks involved in producing the Transbus design outweighed the benefits.[2]

The New York City Transit Authority placed an order for 851 Grumman Flxible 870 buses. Built in 1980, this order brought to light a design flaw in the frame design of the 870. Serious cracks that developed forced the buses from service and prompted legal action between Grumman, Rohr and the transit authority. Grumman agreed to rectify the problem on the existing buses. According to a Grumman spokesperson, engineers had designed the undercarriage of the 870 to save weight. This was a new design consideration for buses at the time, and they did not anticipate the metal fatigue the buses experienced on the poor road conditions in New York.[3]

Grumman submitted an 870 to tests on what they believed to be one of the more deteriorated streets in New York. Data collected from the tests was used to redesign the frame of the bus. The redesigned 870 became known as the Grumman Metro. It would continue to be built under the Flxible name after Grumman sold Flxible to General Automotive Corporation in 1983.


The model designations carried over from the third generation Flxible New Looks:

Nominal seating capacity Width Engine type Air conditioning
35 = 30 ft
45 = 35 ft
53 = 40 ft
096 = 96 in
102 = 102 in
-6 = Detroit Diesel 6V711
-8 = Detroit Diesel 8V712
-0 = No air conditioning
-1 = Air conditioning

1. Some 1981–1983 units used the Detroit Diesel 6V92TA, including 1981 models which went to New Jersey Transit and Santa Monica Municipal Bus Lines.
2. Some 1978–1981 units used Cummins VTB903, including a few from 1978 which went to the Metropolitan Atlanta Rapid Transit Authority.

Beginning in April 1980, the model designation was revised, with the first two digits now indicating length instead of nominal seating capacity:

Length Width Engine type Air conditioning
30 = 30 ft
35 = 35 ft
40 = 40 ft
096 = 96 in
102 = 102 in
-6 = Detroit Diesel 6V711
-8 = Detroit Diesel 8V712
-0 = No air conditioning
-1 = Air conditioning





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Demonstrator/engineering units

Below is a list of demonstrator and engineering buses

Fleet Number Thumbnail Year VIN Engine Transmission Notes
? ? 090001 "Hi Value bus"
1-3 1974 090002-090004 Transbus prototypes
? ? 090005 "Metrobus"
? 1976 090006 870 prototype - 29 inch floor height
? ? 090007 870 prototype - 34 inch floor height
? 1978 090288 Cummins VTB-903 Allison V730
  • 53102 demo.
  • Built to MARTA specs.
? 1979 090911 Detroit Diesel 8V71TA Allison V730
100 1979 091179 Detroit Diesel 8V71TA Allison V730
  • 53102-8-1 demo.
  • NYCTA demo.
? 1981 BD093121 Detroit Diesel 6V71T Allison V730 40102-6 plywood floor demo.
? 1982 CD094239 Detroit Diesel 6V92TA Allison V730
? 1982 CD094607 Detroit Diesel 6V92TA Allison V730

Preserved units

Year Thumbnail Serial Original Owner Fleet Number Current Owner
9/1979 091535 Valley Metro (Roanoke) 186 Commonwealth Coach & Trolley Museum.
1980 091892 NYCTA 236 NYCTA.
1980 NYCTA/NJ Transit 401/1596 New Jersey Transportation Heritage Center
1980 NYCTA/NJ Transit 465/2089 Classic Bus Owners Association
10/1981 BD093725 Southwest Ohio Regional Transit Authority 117 Cincinnati Transit Historical Assn.
12/1981 NJ Transit 1128 New Jersey Transportation Heritage Center.
12/1982 CD094182 Toledo Area Regional Transit Authority 309 Ohio Museum of Transportation


  2. 2.0 2.1 Katzman, Robert A. Institutional Disability: The Saga of Transportation Policy for the Disabled. 1986 Brookings Institution Press: Washington.
  3. Dunlap, David W. 10 October 1981. Grumman Finds Perfectly Aged Potholes for Testing Buses. The New York Times. Chicago, IL.