I am not a bicycle mechanic by any means — for years, I had only ventured as far as fixing a tube, or changing a tyre — but my chain broke while doing unnecessary effort uphill, and were it not for my really handy friends, I would have a had a very unpleasant afternoon.

Every opportunity to fix something is an opportunity to learn. Try to keep this in mind, even when you are working on that flat tire, in the rain, at night, in the cold. More than just learning on bike repairs, also try to learn from any issue that needs repair. Leaky faucets, a computer problem, a squeaky door, all things mechanical things offer chances to apply basic concepts of leverage, friction, tension, material strength, bonding and, hopefully, logic.

from Big Blue Book of Bicycle Repair

In the beginning of 2026, as Copenhagen hit the coldest winter in some twenty years, my bicycles faltered in really obscure ways: the green Scott jumped gears and produced drivetrain failures so violent and loud as little metalic explosions, while the Steamroller would gracefully and disinterestedly disengage my pedalling, with my forward motion to fall into an unexplicable void. The latter problem got worse and worse, to a ridiculous point where my pedalling would not always engage the wheel rotation; when it did, I would ride it as if it were a fixie, as coasting would inevitably disengage again.

I now know what the problem is, and I strongly suspect what the causes are. But the solution came by chance, as I told of my struggles to all those willing to listen. A Danish friend proposed a few possible causes, and the last came almost for the sake of amusement, an outlandish hypothesis: due to the sub-zero temperatures, it could happen for the grease in contact with the pawls (...what?), situated in the internals of the freehub (...err...), to expand due to freezing (...I suppose?). It seemed a little absurd and almost folkroric... until I realized that the problems went away after both bicycles stayed just a few minutes indoors.

Here: this is what makes the wheels engage.

Did I fix anything yet? Other than the more-than-a-dozen punctures in 2025 (and at least two as of March of 2026)