My son has acquired a best friend. This friend is so good that when the two of them are together in my house, I am hardly aware of their presence. Chris’ temperament is reasonably mellow, and so is Ethan’s. This means that instead of trashing my living room by breaking furniture or shooting soccer balls into the TV, they trash my living room by building Star Wars way stations with Legos, magnets, Lincoln Logs and railroad tracks pilfered from old Thomas the Tank Engine parts. They then don Harry Potter attire and conquer the universe in the backyard.

Ethan, however, rides BMX. Ethan’s mom, even, rides BMX. I find this totally cool, especially since I know squat about BMX and so rely on her expertise to introduce my son to the sport. Keep in mind I don’t even know what BMX stands for (bicycle moto-cross?), much less what a BMX bike looks like. This becomes apparent when we stop at a local bikery to pump up the tires of his “normal” bike and I ask how much they sell BMX bikes for. “About $300,” says the clerk, and I go, “Oh,” in that sheepish way you do when you know there is no way in hell you are going to pay that much money for something. But with the bravery of the naive, I caress the handlebar of a nearby steed, and ask Chris, within embarrassing earshot of the store clerk, “is that a BMX?” No, he says, it’s a plain old mountain bike. I decide I really ought to stop faking it, and head us off to the track.

Revelation occurs once I figure out where the track is (this involves, of course, calling Ethan’s mom). Until then, I had stuffed BMX under a subheading of ATV wannabes, as if one might train on BMX just to graduate, somewhere in high school, to loud, mechanized vehicles of the sort that destroy wilderness or any quiet experience of it. But what greets me instead are concentric circles of sculpted dirt hills of varying heights and lengths. Watching Chris swoop around those is a bit like watching a kid self-powering a roller-coaster. It looks like a blast. Pedal really hard up the hill and then SWOOSH! down, bottoming out your stomach. I want a BMX bike at this point.

While he exerts himself in the morning sun (fantastic, I think; he’ll be tuckered out the rest of the day), I ogle a For Sale sign posted up by the bleachers. $125 for a used BMX. Feeling bold, I call the guy. “Do you still have the BMX bike for sale?” I ask.

“Which one?”

Which one? I draw an utter blank, the kind that can precede panic if you’re not careful. He’d only mentioned one bike, or so I thought, on the sign. “Uh,” I say. But then he says, “I only have the Mini left. I sold the other one.”

What’s a Mini? Jeez! By now I’m knee-deep in my own doo-doo. “Uh,” I say again. “What size is a Mini?”

“How old’s your kid?” He asks this in a kindly voice, as if he knows by now he has a clueless parent on his hands.

“Nine,” I say, relieved to have a question I can answer with certainty.

“Yeah, Mini’s are for five-year-olds or so.”

“Ok, well, thanks.” End of call.

I sit there faintly dizzy from dipping my toe in such strange waters. But I did it! I called a guy out of the blue about something I had no idea about! And I learned about Minis and pricing and what I would do for my kid if it’s something that turns out to be healthy and fun, and is tied to a deeply important relationship.

Chris smiles at me from across the track as I fold my cell phone back into my purse. It is truly glorious, this spot by the river. Two little tykes show up — one cannot be older than five — and promptly whip Chris’ butt. But he doesn’t care. He just sits there grinning at me between laps, and all of a sudden I’ve got this kid pedaling us both off into next frontier of bicycles and friendship, and pleased as punch about it.

Katharine Niles is the author of the award-winning novel The Basket Maker.