If you think about it bikes are perfect for a post apocalyptic scenario, specifically mountain bikes.
- They use standard parts that you can find in an any abandoned bike store or department store
- Great for rough terrain that hasn't been maintained
- Significantly less moving parts and easier to maintain than a car
- You wont get trapped inside a bike
- You won't run out of fuel
- If the apocalypse started recently and infrastructure is still usable you might be able to use ebikes that can go absurdly high speeds
Now lets imagine how it effects the story:
- You can dramatically show someone tired desperately trying to bike faster than a zombie crowd
- You can show cool scenes with people on bikes swerving through a crowd of zombies