What is the mandatory minimum percentage of the tractor's actual gross weight that must rest on the front steered axle for safe driving on public roads?

1. At least 80 per cent of the mass must rest on the front axle
2. No minimum applies, provided the rear wheels are braked
3. About 20 per cent of the tractor's mass should remain on the steered front axle, which is why front ballast is fitted with a heavy rear implement
4. Exactly 5 per cent, whether the road is dry or wet