Two Tired

The 11-year-old's rear bike tire just can't seem to hold air.
Two days after we bought it, the tire was flat.
"Have you been doing tricks with it?"
"No."

The leak was patched, and days later the tire was flat, again.
"Have you been jumping off curbs with it?"
"No."

Everyday, we'd wake up and the tire would be flat.
So, every day the 11-year-old would get out the hand pump and pump it up again.
"I just can't understand why it's always the back tire," I wondered aloud one day. "Your other bike always got flat in the back, too."

Then, over the weekend, as the boys and I biked to the grocery store, the 11-year-old called out, "Hey Mother! Watch how long I can do a wheelie!"
And he did. For an impressive amount of time.

The 13-year-old leaned over and said to me, "You wonder why his front tire never goes flat?" He gestured toward the wheelie. "It's because he's never riding on it."