For 1951, the Cooper Mk V (T15) introduced a number of new features. For the first time, the body body panels were completely detachable and the upper panels hinged to improve access. Twin pannier fuel tanks were introduced on either side of the car, and the body shaped changed significantly to accommodate this and to reduce frontal area. The dummy grill remained but served no real purpose as the cooling duct was removed. Instead, a scoop was added under the cockpit which deflected air by the oil tank (mounted behind the driver seat to the engine.

The box section chassis frame remained, in a modified form, with parallel tubes running above and vertical bracing tubes linking the longitudinal members to improve rigidity. A pump was mounted on the back axle to take fuel up to the small tank behind the drivers head which, in turn, used gravity to feed the carburettor. Newton dampers were used. List price was £500 without engine or £582 with a JAP, excluding tax.  A long chassis version (T16) for 1,000cc and 1,100 engines was also offered and a streamlined body was constructed for record attempts (T17).

New customers included Bernie Ecclestone and the semi works team of Ecurie Richmond, with Eric Brandon and Alan Brown driving. The works team drivers were Ken Carter and Bill Whitehouse. One car was specifically built for Festival of Britain exhibition. John Cooper was now so busy, building cars, that he only managed the occasional race. The season reaped nearly sixty outright victories for Cooper 500s compared to the next best performance of 24 for Kieft.

Simon Frost's car at Anglesey in 2005

A paddock shot of Ian Gordon's Mk V at the Monterey Historics 2006 by Stan Anderes.

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Team Transporter for 1951

A modified car (T17) featuring a streamlined body for record attempts and, occasionally, on fast circuits. This is how it was reviewed in "The Autocar" in September 1951.

The streamlined car was used at Montlhery in October 1951 where it set new records for 50km, 50 miles, 100km, 1hour, 100 miles and 200 km in the 350cc class (John Cooper) and 500cc class (Bill Aston) at 91 mph and 99 mph respectively. The team returned in October 1952, failing to run due to snow, and in October 1953 (with a streamlined Mk VIII) when they achieved 104 mph in the 350cc class (John Cooper) and 111 mph in the 500cc class (also John Cooper) over the same distances plus a new record for 200 km in the 750cc class at 114 mph.

The streamliner Mk V at the high speed Avus Circuit in July 1953 with John Cooper at the wheel. It won, in spite of the collision early in the race, the results of which can be seen.