Tanzania at 15 M.P.H.

THE sun is sinking, the air is cooling and our legs are pumping up and down, powering us toward a horizon unbroken by a cellphone tower, a house or even a fence. I'm looking over the bicycle's handlebars at the veld unfurling in front of me - the baobab trees in bloom, the hawks circling, a miniskyline of anthills rising in the distance, thinking that 15 miles per hour is about the perfect pace to soak this all up.

The tandem bike, ridden by the author, in white, and his friend Roko Belic, passed charcoal sellers near Kintinku on their 16-day trip.

And then along come the flies.

All of a sudden, dozens of sizzling black flies descend on me, crawling into my eyes and dive-bombing into my nostrils. I claw at my face and swat my ears and nearly wipe out trying to defend myself. My friend Roko Belic, who just finished making a movie about Hindu spirituality, tells me "be one with the flies."

I just want to be one with the fly swatter.

But that's the deal with biking. Especially in Africa. For better and for worse, it guarantees a certain degree of intimacy - with the bugs, the bumps, the hills, the heat, the people and the mind-blowing, almost spiritual, emptiness.

As you pedal along, you catch all these little details, like the lines in people's faces as they watch you pass by. You feel how the land climbs and sinks, how huge clouds creep across the earth. And you come in contact with all types, like the time we shared the meager shade of a thorn tree with some Masai herdsmen, who, save for their plastic sandals, were still following an itinerant life that is hundreds, if not thousands, of years old.

I'd always wanted to take a trip like this. I don't bike much at home - as a matter of fact, I don't even own a bicycle. But I'd been to Tanzania several times before, having studied Swahili in college and worked for Save the Children in Ethiopia, and the area always struck me as ripe for bike travel because of the temperate climate, the empty roads and the exceedingly friendly people.

The exercise angle was also a big draw. It's one thing to duck inside a gym a few days a week to run in place. It's a whole other to sync up with the sun, embrace the elements and use that cardio time to actually get somewhere.

And now comes the twist. Instead of lighting out for the countryside on two mountain bikes, Roko and I concluded it would be more fun to do it on one - a double bike. Why? I don't think we had a really good answer.

Our friends thought it was kind of juvenile. Our girlfriends thought it was kind of weird. But the two of us had logged thousands of miles together and we were banking on the fact that our friendship could withstand our spending an entire vacation inches apart.

And so for our trip last fall, we mapped out a course of about 770 miles, a mostly straight shot west from Dar es Salaam, on the Indian Ocean, to Kigoma, on the shores of Lake Tanganyika, a ride that could take about 20 days.

Tanzania is a bit of a mzungu (or tourist) playground because of its spectacular wildlife, though I've always felt the country doesn't get the full credit it's due. It may be dirt poor, but it's more or less equally dirt poor, without the class or tribal strife that has ripped apart so much of Africa. Whatever the leaders of Tanzania have done wrong since it was formed in 1964, they've done a few things right, like instituting the use of one language (Swahili), creating a sense of nationhood and delivering decades of peace.

"Hakuna vita," is a favorite expression. It means there is no war, and when your borders touch Rwanda, Burundi, Mozambique and Congo, that's no small feat.

Before we set off, I flipped through a book called "Bicycling in Africa: The Places in Between," by David Mozer. It outlines the basics, like what to bring, how fast to pedal and how to avoid getting sick or hurt.

In the book, Mr. Mozer emphasizes that you don't have to be Lance Armstrong to enjoy a long-distance bike trip. You can adjust the itinerary to suit any level of fitness, from a few miles a day to more than a hundred. Mr. Mozer has led countless weekend riders through all parts of Africa from Tunisia to Botswana, and he told me that his customers, "tend not to be flashy bicyclists or the type to worry if their gloves match their helmets."

Sticking to that spirit, we bought a 0 Raleigh Companion from a San Francisco bike shop, where Roko lives, and outfitted it with saddle bags, extra pumps, fortified rims and Kevlar tires that were allegedly thorn proof. There's actually a number of double bikes that would have done the job. We just picked the cheapest.

The first day was a cinch. (Well, almost a cinch, except for the throbbing pain in our rear ends.) The roads were as smooth as any in the States. The skies were mercifully overcast. And the temperature no more than 80.

JEFFREY GETTLEMAN is reporter for The New York Times.