Alesi's accident increases fears over flying wheels

The massive accident in which Jean Alesi and Kimi Raikkonen ended their Japanese Grand Prix on Sunday yet again raised questions about the effectiveness of the so-called wheel tethers that are used to stop wheels flying in all directions when F1 cars crash.

In several big accidents this season, including those which befell the Prost driver Tomas Enge and Sauber's Nick Heidfeld in Suzuka on Friday, the tethers have failed to keep the wheels attached to the cars. Raikkonen's car lost three of its wheels, and the fourth was almost detached.

The safety and insurance implications are foremost in F1 officials' minds. In 1986 at the Indianapolis Motor Speedway a spectator, Lyle Kurtenbaum, was killed by a flying wheel and his widow received a sizeable pay-out. In 1994 another wheel, from a collision on the start line between J J Lehto and Pedro Lamy in the fateful San Marino Grand Prix at Imola in which Ayrton Senna was killed, actually cleared the main grandstand on the left of the track. As it landed it seriously injured a policeman.

Following that incident the sport's governing body, the FIA, initiated investigation into means of restraining wheels. Before the fruits of that could be implemented, a multi-car pile-up in the Belgian Grand Prix in 1998 raised the issue once again, as wheels were thrown perilously close to spectators.

Single tethers became mandatory in 1999 and initially proved effective. Since then there have still been serious incidents involving detached wheels, even though double tethers came in for 2000. At Monza last year, on the opening lap of the Italian Grand Prix, a wheel from Heinz-Harald Frentzen's Jordan struck and killed a marshal, Paolo Ghislimberti. Debris from Jacques Villeneuve's accident in this year's Australian GP in Melbourne, which included flying wheels, struck and killed a crowd marshal, Graham Beveridge.

This has led to criticism of the tethers and calls for them to be strengthened. However, it is not a simple situation. A lot depends on the nature of the accident.

Currently there are two steel tethers per wheel, with a combined breaking strain of 10 tonnes. It is quite clear, however, that recent accidents have imposed even greater forces.

Initially, the single tethers proved too strong and tended to damage the carbon fibre monocoque chassis, as they tore out suspension mounting points. This was clearly untenable, given the cost implications. But it was only later, when wheels started coming off again during impacts, that the FIA's engineers were obliged to have another look and introduced two tethers.

"The thing is, the tethers have 5,000 kg (11,023 lb) breaking strain, and you can generate forces greater than that, never mind any cutting action or what have you," says the FIA technical delegate, and former Lotus designer, Peter Wright. "So under certain circumstances they are going to fail, and there's not much you can do about that. If you trap a wheel against a barrier or something, and then drag it, you are basically not going to stop the car from tearing the wheel off itself."

That is precisely what happened when Alesi's car trapped Raikkonen's against the wall. The front wheels of Alesi's car were also torn off their suspension mountings in the incident, but remained attached to the car by their tethers.

The difficulty lies in deciding where the tethers should yield. The belt and braces concept of two tethers has proved effective, since breakage of the first absorbs a lot of the energy and therefore gives the second one, which is the stronger, a much better chance of doing its job. But the system is not infallible. Further studies are being carried out, with the possibility that triple tethers may be introduced.

FINAL POSITIONS

DRIVERS' CHAMPIONSHIP

1 M Schumacher (Ger) Ferrari 123pts; 2 D Coulthard (GB) McLaren-Mercedes 65; 3 R Barrichello (Br) Ferrari 56; 4 R Schumacher (Ger) Williams-BMW 49; 5 M Hakkinen (Fin) McLaren-Mercedes 37; 6 J P Montoya (Col) Williams-BMW 31; 7 N Heidfeld (Ger) Sauber-Petronas 13; 8 J Villeneuve (Can) BAR-Honda 12; 9 J Trulli (It) Jordan-Honda 9; 9 K Raikkonen (Fin) Sauber-Petronas 9; 11 G Fisichella (It) Benetton-Renault 8; 12 E Irvine (GB) Jaguar 7; 13 H-H Frentzen (Ger) Prost-Acer 6; 13 J Alesi (Fr) Jordan-Honda 6; 15 O Panis (Fr) BAR-Honda 5; 16 P de la Rosa (Sp) Jaguar 3; 17 J Button (GB) Benetton-Renault 2; 18 J Verstappen (Neth) Arrows-Asiatech 1.

CONSTRUCTORS' CHAMPIONSHIP

1 Ferrari 179pts; 2 McLaren-Mercedes 102; 3 Williams-BMW 80; 4 Sauber-Petronas 22; 5= Jordan-Honda 17; BAR-Honda 17; 7= Benetton Renault 10; Jaguar Racing 10; 9 Prost-Acer 4; 10 Arrows-Asiatech 1.