I am planning a month long trip from Beijing to Western Sichuan and back, and I was hoping to put on some more aggressive tires on my Zongshen RX-3. I'm looking for a somewhat knobby tread designed for maybe 60% off road 40% on road, but apparently its very difficult to find this type of tire for a 15" wheel. The bikes wheel specs are below:


Front: 100/R90-18″, Tube Type
Rear: 130/R70-15″, Tube Type

Anybody have any recommendations?

Thanks,
Steve