Police said a ute going in the opposite direction to him near Taupo passed another vehicle.
Mr Slade believed the ute came too close to him and made a finger gesture to the driver.
The ute driver, dairy farmer Joseph Arthur Frederick Roberts, 21, allegedly turned back, passed Mr Slade, got out of the vehicle and pushed him off his bike.
Roberts was charged with injuring with intent to cause grievous bodily harm.
From hospital, Mr Slade said: "Every cyclist has a bullseye on his butt."
Road rage between cyclists and motorists is rare, says Cycle Action Auckland chairwoman Barbara Cuthbert.
Actual violence - such as the hot coffee thrown on a cycle courier by a driver in Canada, or the cyclist who stabbed a motorist with a screwdriver, also in Canada - occurs infrequently in New Zealand.
An American cyclist was tackled off his bike and punched by a motorist in Wellington last year.
More frequent is fist and finger waving, shouting and swearing, when cyclists and drivers assert their versions of who is in the right. And with a near-10 per cent increase in cyclists on monitored Auckland roads and cycleways last year, the competition for space will only intensify.
Bike-vehicle crashes put 300 cyclists a year in hospital, and on average kill 10.
One was Wellington policeman Superintendent Steve Fitzgerald in 2008. That case led a coroner to urge that cyclists be required to wear high-visibility clothing.
A cycling advocate dismissed the coronial recommendation, saying safer roading was needed, such as the separation of cycle and vehicle lanes on busy streets.
Commodore Car Club president Dennis Anderson said that in disputes on roads, "everyone needs to count to 10 before they do anything".
"I don't mind cyclists being on the road as long as they obey the rules. It's just the odd one that thinks they can get across on a red light. It's the odd idiot and, to be honest, there is the odd idiot in cars too."
Mr Cornwell, who is recovering from surgery after he was hit from behind and suffered back injuries, said he had experienced similar incidents to Mr Slade's when training solo in the Waitakere Ranges.
"I've had to pull over and stop in the gutter."
He disagreed with the advice of Cycle Action Auckland to give "a wave and a smile" when motorists behaved badly.
"I'm not going to smile and wave when someone does that. I wouldn't do the fingers. Sometimes it's just a reaction, adrenalin pumping and you yell and swear, but it's not the best thing to do. You need to make them aware, like shaking your fist or throwing your hands up in the air and saying, 'Look out mate'.
"If the driver acknowledges they made a mistake, in that situation you don't want to abuse them."
He had never been chased and confronted like Mr Slade, but he had been followed from one set of traffic lights to the next in an intimidating fashion.
He said cyclists needed to be ultra-defensive and be prepared for every parked car to pull out in front of them or have its door flung open.
