In recent days my fellow Peak Pedalers have offered advice about what to pack for RTR, and how to pick the right kind of lodging.

They are wise guides. Take good notes and heed their advice.

Then, light a votive candle for the Modanna del Ghisallo. For all your careful planning and packing, sometimes it helps to have guardian angel along for the ride, all 513 miles of it.

Kathy and I felt the touch of our RTR angel in 2011 near the top of Rabbit Ears Pass. We had just begun our descent. Several miles of steep downhill lay ahead.

Now, mountain descents are the reason why cyclists get up in the morning, but at the same time, they are serious business, especially on a tandem, because the most urgent reality about a tandem is this: Descents can kill you.

With twice the weight of a single rider on its two wheels, a tandem can quickly get up to dangerously high downhill speeds. With the aid of a stiff tailwind, we once topped out our Burley Duet at 53 mph, but the curves were gentle, the grade was not too steep, and there was plenty of flat, straight runout at the bottom.

That kind of speed on a steep, switchbacked mountain descent is suicide. Brakes? When there are 300 pounds on two wheels pointed down a 6 percent grade, brakes will heat the rims so hot they’ll blow the tubes, sending you 50 mph into a hairpin with a flat tire.

A drum brake on the rear axle keeps the tandem from gaining too much speed.

That’s why, before bike disc brakes came along, tandems were equipped with a drag brake. Fixed to the rear hub, it’s a bike-sized version of the standard automobile drum brake. Activated by a friction lever on the handlebar, the drag brake is like an anchor tossed out behind the tandem, preventing speed from getting too high the first place, making it possible for the rim brakes to do their job without overheating.

Feeling for the lever and testing out the brake is something I do automatically as we begin a major descent. It was no different as we rolled away from the top of Rabbit Ears Pass and began to pick up speed.

We were accelerating past 30 mph. I reached to the end of the drops, and gave the lever a pull. Nothing.

I looked down, in a panic. The brake cable was completely slack.

I grabbed the rim brakes before the situation could become a complete runaway, and brought the bike to a stop. The screw that had held the drag-brake lever under tension was gone. I never saw it pop out while climbing up the other side of the pass. Now, ahead of us was miles of black-diamond steeps, too deadly to ride without the drag brake. Behind us was most of an uphill mile back to the aid station on top of Rabbit Ears — where, of course, we had passed a Shimano van, parked on the side of the road with two mechanics and a bike-shop’s worth of tools and supplies inside.

The drag-brake activation lever — and the emergency parts scrounged off the Shimano van during RTR 2011 that restored its operability.

“You know what we need right now,“ I said to Kathy, looking up to the top of the hill. “We need the Shim–”

And there it was, cresting the hill behind us, rising into view. Ten minutes and some odds-and-ends parts later, we had a functioning drag brake. The blue Shimano van rolled away.

Somewhere along the ride, you might need a bit of good fortune. Or maybe you will be the stranger who appears out of nowhere to help someone who’s in a bind. All sorts of things can happen on the open road, under the open sky, among 2,000 people riding mechanical objects that often break down in unforgiving locations. We plan the little things we can control, so that we can be ready for the big, unpredictable things that will come our way. And those are the moments we will remember.

With our brake fixed, we sailed down the long, winding descent from Rabbit Ears Pass. Toward the bottom, as the road straightened out, I released the drum brake and we shot off the mountain and into the flats, as if on the wings of angels.