Factory error caused Kovalainen shunt.

McLaren has revealed that a mistake made in the preparation of its wheels for the Spanish Grand Prix led to Heikki Kovalainen suffering a high-speed impact with the tyre wall while poised to challenge for victory in Barcelona.

The Finn had moved into top spot in the first European round of the season after running a heavier initial fuel load than his rivals, but speared off at around 145mph when the left front wheel appeared to fail entering turn nine at the Circuit de Catalunya. The failure, in turn, punctured the left front tyre on the MP4-23, and the car plunged across the gravel trap before burying itself deep under the tyre wall.

Now, two months after the incident, McLaren has revealed that a thorough investigation, conducted in conjunction with wheel supplier Enkei and the FIA, into the causes of the accident has finally revealed the reason why Kovalainen went off where he did, both confirming and denying initial suggestions of rim failure caused by unusual wear on the wheel.

Team CEO Martin Whitmarsh explained that the central area of the offending rim had been left unmasked before being sprayed with lacquer, and the resulting lacquered surface reduced the wheelnut's grip on the rim, allowing the wheel to rub against the brake drum. That, in turn, caused unusually high wear on the rim, leading the sudden failure.

"The investigation not only involved thorough scrutiny of the telemetry data and a microscopic analysis of the surviving components, but also a simulated reconstruction of the event back at the McLaren Technology Centre," Whitmarsh told journalists at this week's Silverstone group test, "We now thoroughly understand how the failure occurred - not, as was originally reported, as a result of a wheel failure, but by the incorrect application of a lacquering process which was beyond the control of our wheel supplier, Enkei, with whom we have enjoyed a fantastic relationship for more than ten years."

The lacquering process has now been revised to ensure that there can be no repeat of the mistake.