We have had a few questions over the years of people wanting to cycle in Afghanistan. The security situation is obviously reason for concern, and we hope you understand the risks involved.
Here is an excerpt of what the last cyclist we knew wrote to us.
I cycled in Afghanistan for one month and was later captured by government, they thought I was a spy and sent me to jail, finally got deported to Tajikistan. Westerners are being kidnapped and killed every year, please DO NOT travel by bicycle to Afghanistan, since you will bring trouble to your family and your country.
Travelers who survive Afghanistan do not do so because they are smart, they were just lucky. Hope you can advice traveler not to travel in Afghanistan by foot or bike. (this conclusion is based on my discussion with Taliban people in prison).
Questions and reports are welcome in the Afghanistan cycling forum thread.
An exception to this basic rule would be cycling in the Wakhan corridor. A good mountain bike, lots of spare parts and mechanic skills and an above-average level of fitness is required.