1955 Mk IX (T36/T37)
1955 Mk IX (T36/T37)
| Introduced for 1955, the Mk IX represented the last real evolution of the Cooper 500. The car made its debut on Boxing Day '54 at Brands Hatch and helped Les Leston to clinch the title. For '55, the works cars were driven by Jim Russell and Ivor Bueb, winning 15 out of 28 races, and earning Jim the Formula 3 Championship with Ivor second by a point. Ivor also won the Irish Championship in '55 and ran his Mk IX under the banner of Ecurie Demi-Litre through 1956 and '57.
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| The principle developments from the Mk VIII, were: An overall lowering of the car. This was achieved by means of flattening the springs to lower the ride height, lowering of the scuttle and seat hoop chassis tubes and and by flattening the fuel tank (still above the drivers legs). The introduction of a single, centrally mounted disk brake at the rear, replacing the pair of drums on each wheel. This reduced overall and un-sprung weight but caused mixed reactions from the drivers as, while the disk brakes are undoubtedly more effective, the mixture caused the front and rear brakes to "come in" at different rates. Roll stiffness was introduced at the rear using a centrally mounted curled leaf spring as had been the practice at the front for the Mk VIII.. The leaf spring mounting rollers were moved further apart to 15 1/2 inches at the front and 12 inches at the rear to increase overall roll stiffness. |
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| The rear uprights were now made from magnesium alloy to reduce weight and the Armstrong dampers were re-sited to allow more vertical alignment (following Beart practice). The 18 gauge aluminium body was retained however Cooper did experiment with glass fibre mouldings. GRP was then in its infancy and early attempts were unsuccessful however later cars did appear with glass fibre bodies. Overall the Mk IX was lighter, lower and slimmer than the Mk VIII. Wheelbase was 7ft 3in, front track 3ft 9in, rear track 3ft 7in. The height was only 2ft 7in to the top of the screen and body was only 1ft 11 1/2 inches wide. Officially the production cars weighed 530lbs dry with a Norton engine although works cars featured lighter chassis tubes. Ivor Bueb's car was reduced to under 500lbs to compensate for his 15 stone frame. The price was £620 without engine or £718 with a JAP 500 fitted. Two versions were offered for 500cc (T36) and 1,000cc (T37). | |
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By 1955, Cooper domination of Formula 3 was almost total with only Don Parker's Kieft offering any really consistent challenge. In line with Charlie Cooper's views on not changing something that was working so well, all subsequent Cooper 500 cars were almost identical to the Mk IX although new Mk numbers were issued each year.
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