by Michael Clark » Sun Apr 07, 2013 1:21 am
This is an abbreviated version that was part of a column I did for NZ Classic Car on the 40th anniversary of Clark's death:
Chris Amon (who was a short distance behind the Lotus of Clark in the Scotsman’s final race)– “Jimmy’s death affected me more than any driver I competed against, other than Bruce (McLaren). It was huge - not only am I certain that it wasn’t driver error, I’m virtually convinced that it wasn’t the ‘explosive decompression of a tyre’ – which was determined as the cause at the time. Firestone took it on the chin after the enquiry but I’m not convinced – I’m not sure if anyone considered in the circumstances that existed at the time, i.e. the level of grip required to negotiate the corner in the conditions that any sort of failure of the right rear tyre is unlikely to have caused a loss of control. That corner could have been negotiated at much higher speeds than the cars were capable of at that point on the circuit. I’d still like to see the truth come out – it won’t bring him back but because of his place in history, we owe it to him. You can’t have an ‘explosive decompression’ of something with no air in it. If it was a slow puncture, doesn’t that mean the tyre was low on pressure? So how does it explode? I was the next car behind him – if he was slowing, why wasn’t I catching him? Did anyone check whether the tyre colour changed? Rubber will change colour when a tyre is run at low pressure – even in the wet. In any event, a flat tyre on that curve would not have made a blind bit of difference, as there was a huge margin of error – and the right rear was not the tyre under load on that curve…but a right rear suspension failure would have caused it. A friend of mine is a highly competent tyre engineer who has considerable expertise in vehicle dynamics, having been employed for a period on chassis and suspension development and, at the time of the accident, was employed as a race tyre development engineer. Having done tens of thousands of miles of both tyre and suspension testing, I like to believe I have a basic understanding also of vehicle dynamics. He told me that when he examined Jimmy’s tyres, along with the wreckage, at Farnborough, that he observed large braking flat spots on the left front and right rear tyres, in both cases covering the full width of the tread, very light scuff marks on the right front and slightly more pronounced ones on the left rear. I believe it would be reasonable to assume that this would indicate very heavy braking just prior to impact. These marks simply do not support the view that the right rear tyre was either flat or very under inflated at the time of the heavy braking, but they do support the very real possibility that the left rear suspension had failed and that the left rear was being supported by only the rear anti-roll bar. People suggested bolts in rims to stop tyres pulling off the bead but from memory the tyres at the time were still 4-ply construction and these bolts did not happen until construction went to 2 ply in the early seventies. In all the years that have passed since the accident, I have always had a problem believing that a failure of the right rear tyre was the cause. I was running identical tyres that day, lapping at a very similar speed, and I can say with almost 100% confidence that had I suffered a failure of the right rear tyre at the very same spot, I do not believe it would have resulted in an accident – there was just not sufficient cornering load on the car for an inside tyre failure to have been a major problem at that point. I don’t normally get involved in these sorts of matters however I feel strongly that it would be nice if the circumstances surrounding the demise of a person who was, is and always will be such a hugely important part of the sport and it’s history, had a reasonable chance of being factual.
This is an abbreviated version that was part of a column I did for NZ Classic Car on the 40th anniversary of Clark's death:
Chris Amon (who was a short distance behind the Lotus of Clark in the Scotsman’s final race)– “Jimmy’s death affected me more than any driver I competed against, other than Bruce (McLaren). It was huge - not only am I certain that it wasn’t driver error, I’m virtually convinced that it wasn’t the ‘explosive decompression of a tyre’ – which was determined as the cause at the time. Firestone took it on the chin after the enquiry but I’m not convinced – I’m not sure if anyone considered in the circumstances that existed at the time, i.e. the level of grip required to negotiate the corner in the conditions that any sort of failure of the right rear tyre is unlikely to have caused a loss of control. That corner could have been negotiated at much higher speeds than the cars were capable of at that point on the circuit. I’d still like to see the truth come out – it won’t bring him back but because of his place in history, we owe it to him. You can’t have an ‘explosive decompression’ of something with no air in it. If it was a slow puncture, doesn’t that mean the tyre was low on pressure? So how does it explode? I was the next car behind him – if he was slowing, why wasn’t I catching him? Did anyone check whether the tyre colour changed? Rubber will change colour when a tyre is run at low pressure – even in the wet. In any event, a flat tyre on that curve would not have made a blind bit of difference, as there was a huge margin of error – and the right rear was not the tyre under load on that curve…but a right rear suspension failure would have caused it. A friend of mine is a highly competent tyre engineer who has considerable expertise in vehicle dynamics, having been employed for a period on chassis and suspension development and, at the time of the accident, was employed as a race tyre development engineer. Having done tens of thousands of miles of both tyre and suspension testing, I like to believe I have a basic understanding also of vehicle dynamics. He told me that when he examined Jimmy’s tyres, along with the wreckage, at Farnborough, that he observed large braking flat spots on the left front and right rear tyres, in both cases covering the full width of the tread, very light scuff marks on the right front and slightly more pronounced ones on the left rear. I believe it would be reasonable to assume that this would indicate very heavy braking just prior to impact. These marks simply do not support the view that the right rear tyre was either flat or very under inflated at the time of the heavy braking, but they do support the very real possibility that the left rear suspension had failed and that the left rear was being supported by only the rear anti-roll bar. People suggested bolts in rims to stop tyres pulling off the bead but from memory the tyres at the time were still 4-ply construction and these bolts did not happen until construction went to 2 ply in the early seventies. In all the years that have passed since the accident, I have always had a problem believing that a failure of the right rear tyre was the cause. I was running identical tyres that day, lapping at a very similar speed, and I can say with almost 100% confidence that had I suffered a failure of the right rear tyre at the very same spot, I do not believe it would have resulted in an accident – there was just not sufficient cornering load on the car for an inside tyre failure to have been a major problem at that point. I don’t normally get involved in these sorts of matters however I feel strongly that it would be nice if the circumstances surrounding the demise of a person who was, is and always will be such a hugely important part of the sport and it’s history, had a reasonable chance of being factual.