What do you have to pay attention to, when jacking up a motorbike on its centre stand?

Both aspects you selected are important for safely jacking up a motorbike on its centre stand.

1. The risk of tipping over is critical; even a slight tilt can cause instability. This highlights the importance of a stable surface and proper technique when performing this action to avoid accidents.

2. The difficulty of jacking up the bike on a steep gradient is a practical concern. On inclines, the bike's centre of gravity shifts, making it harder to manage safely.

Together, these points emphasize the need for ensuring stability and safety when performing maintenance on a motorbike, which aligns with the regulations regarding vehicle maintenance and safety in German traffic laws. The third option, while possibly relevant for comfort, is not as essential for safety as the first two, hence it is not included in the correct answer.