Aug.23 (GMM) Spyker has called off the scheduled debut of its already-delayed 'B' car.



On the eve of opening practice for the Turkish grand prix, the Dutch team revealed that the heavily revised single seater last week failed the FIA's mandatory rear impact test.



Adrian Sutil and Sakon Yamamoto must therefore race the uncompetitive A-spec car once again.



The crash test failure was "possibly due to problems with a batch of material used", Spyker's chief technical officer Mike Gascoyne said.



"These tests are quite rightly very stringent and difficult to pass, but we did not expect to have a problem as the structure is very similar to the A spec one," he continued.



Spyker will re-attempt the tests next week, as well as testing the car at the pre-Italian grand prix test at Monza.