The tires can be pumped with a handpump or a pump for car tires. The valve can be pushed to the outside for better access. After removing the cap of the valve and attaching the pump to the valve, you can fill the tires with air. The front wheels can be filled to 4,5 Bar or 65,3 PSI and the back wheels can be filled till 2,5 Bar or 26,3 PSI.