Nakano Air Hubs are a wonderful invention. The hub acts as a small air pump. A tube from the hub to the tube valve stem keeps the tire continuously inflated to 95 PSI.

Here's the explanation from the Nakano Iron Works in Japan:

Being a specialist of bicycle hubs, we have been always monitoring the customer's opinions and noticed that the most important factor that the cyclists are worried about is a flat tire. We have come to know through our investigation that most of the cyclists ride a bike with tires of air pressure at 1.8atm in average in spite of the required 3.0atm.

Less air pressure causes a flat tire, but leakage of the air is inevitable as long as rubber is used inside the tire. An idea to keep pumping the air while riding a bike has flashed into my mind and it seems better to make such a mechanism rather than waiting for a rubber maker to produce leakless tubes.

After spending a lot of time, we have finally developed a hub continuously supplying the tire with the air while cycling.

Here's a Nakano Air Hub installed with its air hose going from the hub to the valve stem.

Nakano Air Pump Front 36-hole Hub. New, $70.00 each

Part# 52045

Here's the hub with its hose and valve connector

Just the Air Hub

Side view

Nakano Air Pump Rear 36-hole Hub, 130mm. New, $70.00/each

Part# 52046

Hub, hose and connectors, it's all there.

Side view of just the hub

Here's the other side

Top view

Another close-up