Engine : Compression ratio 5.1:1 (after 1930 5.3:1) power output 160 bhp at 3,500 rpm or 180 bhp (single port block); crankshaft diameter increased by 8mm (5/16 in) 2 SU carburettors type HVGS
Transmission : C type gearbox (very few had D type)
Chassis : Pressed-steel, parallel girder with one tubular and four channel crossmembers; semi elliptic springs front and rear, tuned to customer's specifications
Dimensions : Wheelbase 3,505.2 mm (138 in), later 3,568.7 mm or 3,873.5 mm (1401/2 in or 1521/2 in)
Performance : Max speed 148 km/h (92 mph)
Radiator Badge : Green enamel
During competition in Britain, particularly at the Brooklands Track, a weak point soon became evident. This heavy car with its powerful engine and high running speeds would soon cause problems with tyres when, even on short runs, the tread would part company from the carcass. Soon afterwards a solution was provided by the Goodrich Rubber Company who, after long experiments, had developed a rubber compound that was reliable when subjected to the punishment meted out by these heavy cars. As a consequence of Goodrich's assistance Bentleys subsequently equipped all their cars with tyres from that company for some time. Because of the tyre problems, several years went by before a 6 1/2 litre was listed as an entry to the classic Le Mans event. By that time the other tyre companies had made progress, so catching up with Goodrich's original developments. Bentley then let his works cars run on Dunlop.
In its first entry in the 24 hour Race at Le Mans the Bentley Speed Six crossed the finishing line as victor.Woolf Barnato, the main shareholder in the company by then, had contributed to this success as co-driver with "Tim" Birkin. He was heir to an immense fortune which had been gained by his family from the ownership of South African diamond mines. Woolf Barnato had widened his business interests to England and the USA and lived mainly in these countries. He was considered a brilliant driver by many including W O Bentley. His belief was rewarded when Barnato achieved the victor's laurels again at the following year's Le Man race, acting as co-driver aboard another Bentley Speed Six, this time with Glen Kidston.
During the two years in which they were in production, the sale of Bentley Speed Sixes reached a figure of182 cars. Very often, because the cars were aimed at a rareified clientele they would be equipped with appropriately lavish coachwork.
Looking back Bentley himself had no doubt that the Speed Six was his masterpiece.There is no doubt that had it not turned up at exactly the wrong time - the dramatic economic decline after that black Friday in October 1929 when Wall Street crashed - the Bentley Speed Six would have been a commercially successful, as well as a technically successful, motor car.