Do bald tyres increase or decrease braking distance?

Bald tyres increase breaking distance.

Bald tyres have significantly less tread than newer tyres, they therefore have much less friction. Less friction results in slower negative acceleration, which means that the car takes longer to slow down, thus increasing the breaking distance.

Bald tyres significantly increase braking distance. This is due to a reduction in grip caused by the lack of tread. Bald tyres also increase the risk of aquaplaning, further compromising braking ability. Aquaplaning occurs when a layer of water builds up between a vehicle's tyres and the road surface, causing the tyres to lose traction.