Suspension fork company Fox Racing Shox claims the accident that left mountain biker Russell Pinder paralysed was caused by his own negligence.
The firm's lawyer told the High Court in London that the cyclist should have checked that the quick-release skewer on his front wheel was done up. He insisted the accident had not been caused by any "defect" in Mr Pinder's Fox Float 100R fork.
Mr Pinder, 44, of Blewberry, near Didcot, Oxfordshire, is now confined to a wheelchair after the front wheel of his bike came loose during a ride in the Brecon Beacons, Wales, in March 2003, and he was paralysed from the chest down.
He blames his Fox fork for the accident and is suing the Californian company for millions of pounds. But lawyers for the company are contesting the claim and argue the crash may have been avoided altogether if Mr Pinder had taken more care.
Andrew Prynne QC, for Fox, told the court the accident happened because the QR skewer through Mr Pinder's front wheel had come loose. He said Mr Pinder should have known this and acted upon it.
"Fox alleges that the accident was caused or contributed to by the negligence of the claimant in riding, or continuing to ride, his bike when he was, or ought to have been, aware of and alert to the fact that his front wheel was, or had become, loose," said Mr Prynne. "Fox submit that, if he had been taking the degree of care reasonably to be expected of him in these circumstances, the claimant could and should have noticed any looseness and taken immediate remedial action."
Mr Prynne said Mr Pinder had been riding substantial distances at high speeds over rocky and hilly terrain at the time of his accident.
He told the judge, Mr Justice Plender: "Mountain biking of this kind and at this level is a sporting activity that undoubtedly places stresses and strains upon both the rider and the component parts of his bike, such as may give rise to a risk of injury.
"Accordingly, Fox maintains that the nature of this undertaking called for a high level of care and vigilance on the part of the claimant in terms of checking the integrity of his bike and its components on a regular basis, and certainly after any mishap, so as to minimise those risks."
Mr Prynne added that the accident had not been caused by any "defect" in a Fox component.
Pinder argues design flaw
Barry Cotter QC, for Mr Pinder, has told the court it is his case that "the design of the forks would, when combined with certain disc brakes, in a certain alignment and when using a front wheel secured by a quick-release mechanism, create loosening of the front wheel after repeated brake application, followed by subsequent ejection of the wheel."
He has argued that Fox is liable to pay damages due to its "negligence" in failing to adequately test the effect of combining its Float forks with a disc brake and quick-release wheel.
Mr Pinder, who was wearing a helmet, sustained devastating injuries in the crash, including severe damage to his spine, which resulted in his paralysis. After his accident, he was airlifted to hospital and later taken to Stoke Mandeville Hospital, in Buckinghamshire, where he stayed for six months.
His lawyers say he is permanently handicapped in his social, domestic and everyday life and has only been able to return part-time to his job at Stephen Russell Construction Ltd, in Aylesbury, where he is a company director and chief estimator.
The hearing, which began last Tuesday, has consisted largely of technical arguments. Several days were spent interviewing witnesses in the US via video-link.
The case has now been adjourned for lawyers on both sides to submit their closing arguments to the judge in writing. A judgment is not expected until later this year.