system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is it that you cannot fix a flat tire if the hole is on the side?

I was told by the mechanic that I need a new tire because I have a flat that is not repairable because the nail penetrated the tire on the side.  He couldn't explain why.
gpt
The tread surface of a tire is much more rigid because that's the part of the tire designed to make contact with the road.  The sidewall is much more flexible because it is designed to adapt to changes in tire pressure without bursting.  Sealing the tread is easy because the patch will remain relatively still, but a patch in the sidewall will be the weak point for a flexible and high-pressure surface.