Which of the following factors can decrease your motorcycle's grip on the road?

Answer: D — Over-inflated tyres

Over-inflated tyres can significantly decrease a motorcycle's grip on the road. When tyres are over-inflated, the contact patch—the area of the tyre that touches the pavement—becomes smaller. This reduced contact patch means that there is less rubber in contact with the road surface, which can lead to decreased traction. In addition, over-inflated tyres tend to become harder and less flexible, which reduces their ability to conform to road irregularities, further impairing grip. In contrast, other factors such as riding in the rain, slightly under-inflated tyres, and worn tyres are also known to negatively affect grip, but they operate on different principles or mechanisms. For example, rain can create a slippery surface due to oils and water mixing, while under-inflated and worn tyres can lead to uneven tread contact and decreased effectiveness. In this case, focusing on how over-inflation specifically reduces the tyre’s contact with the road clarifies why it is relevant in the context of grip reduction.