More gravel is needed to fill the hollow in the drive.

And the wheels have artificial intelligence - they can sense obstructions and potholes in the road.

But if you' re doing hairpin turns on a dirt road in the mountains, slow down.

The undulating, cratered terrain proved too much for the suspension on one of the bikes, causing one rider to pull out.

Every bump in the road - and there are many - sends agonising jolts of pain through my midriff and I begin to think that this trip is over for me.