I will never be smart.

I’m riding the Soma Double Cross on Tramway this afternoon and on the speedy big-ring drop to Interstate 25 I suddenly hear this high-pitched whine coming from what I’m certain is the front wheel. Sounds like a brake shoe rubbing up against the tire, or maybe Jimmy Olsen’s watch calling Superman. Zee zee zee zee zee.

As this can only end badly on a fast descent, I stop — not once, not twice, but three times — to try to diagnose the problem. No joy. But then, as I turn around at the bottom for the climb back up, the noise stops.

Well, OK, then. Ain’t much bad can happen to me at 10 mph. So on I pedal in blissful ignorance.

Until I shift back into the big ring, get out of the saddle to stretch, and hear it again — zee zee zee zee zee.

A light bulb sputters on, about a 20-watter. I’m running the biggest tires this bike will take, 700×38, and I bet the rear tire is heating up and expanding and rubbing up against the front-derailleur mech. Genius!

Well, maybe not so much.

The Double Cross doesn’t have one of those bulky new Shimano mechs that intrude into the rear triangle the way the NSA does into your life. It sports a svelte old Ultegra model.

And, as I found when I got home, it also has a front-derailleur cable that somehow got itself bent inward, and the cable cap was rubbing the rear tire whenever I shifted into the big ring.

So if you’re ever riding with me and wonder what the funny noise is, don’t worry — it’s just the air leaking out of my head.