PC Russ Wylie was on the wrong side of the road when he hit the Mitsubishi Outlander on the B1362 near Burstwick, Holderness, in April.
An inquest in Hull heard today “only Russ would know the answer” as to why he braked.
The impact threw the experienced officer, who was heading out for a coffee with a colleague while on a break, onto the windscreen of the car and then into the air.
A trainee paramedic who was playing golf at Burstwick Golf Club, was the first to the scene to give him first aid.
The emergency services arrived and he was airlifted to hospital, but the 28-year-old died the next day from the “unsurvivable” injuries.
Martin Oliver, who was playing golf with his son, trainee paramedic Matthew Oliver, said he had been startled by a bang as “loud as a gunshot.”
In a statement read to the court, he said: “All my attention was on the figure of a motorbike rider in the air turning head over heels as he was thrown over the roof, turning a couple of times. He appeared as a blur of yellow jacket and white crash helmet.”
The court that there was no evidence that PC Wylie nor Mitsubishi driver Hilary Green was travelling at an “inappropriate” speed.
Mrs Green, of Wyton Lodge, who described herself as a company secretary for her family business, told the court the accident happened “in seconds”: “I just saw two bikes coming towards me and the left hand one was coming onto my side of the road. It was a matter of seconds from seeing them to the impact. I remember thinking: ‘He’s going to hit me’ - and with that he hit me.”
PC Wylie’s colleague, acting sergeant John Rickells said he had been riding behind PC Wylie but “suddenly” caught up with him half way round the corner and noticed he had gone from a leaning to an upright position.
“I saw a light blue coloured Mitsubishi travelling towards us in the opposite direction,” he continued. “As Russ crossed the central line of the carriageway the bike collided with the vehicle on the front off-side corner.”
Senior collision investigator John Rusted said PC Wylie had applied the brakes at the “most inappropriate moment.” He said: “Why he was unable to maintain the radius he seemed to be negotiating and which appeared safe will remain unknown. Only Russ Wylie would know the answer.”
His father John said in a statement being a police motorbike officer was PC Wylie’s dream job. He had passed his advanced motorbike course the year previously with a Grade One pass.
Coroner Prof Paul Marks, who recorded an accidental verdict, said: “I don’t think we will ever know the circumstances of why he braked on that bend at that particular time. Everyone acknowledges that he was an extremely experienced and skilled motorbike rider.”
Afterwards his family, parents Sue and John and fiancee Roxanne, thanked the emergency services and said they had received hundreds of messages from people he had helped, colleagues and those “whose lives have been brightened simply by a smile.”
They added: “We are extremely proud that he achieved his ambition to become a police officer and served the people of Humberside with such dedication.”