SEATTLE -- I don't know exactly how or why it happened, but we are just starting up the hill toward Magnolia Bridge when I turn for some reason, lose my momentum and start tipping over on my bike. Because this happens so quickly, I can't get my cleat out of the Shimano pedal in time and simply tumble over on my side. This happens to me roughly every six months, and it is sometimes painful and always embarrassing. But never so embarrassing as it is now, thanks to the identity of my companion cyclist.

"Are you all right?" Floyd Landis asks, riding over to me. "Did you hurt anything?"

"Only my pride," I assure him. Which is true. I mean, good Lord. I just tipped over on my bike in front of the Tour de France winner. Landis probably thinks that I need training wheels, or that he's riding with Pee-wee Herman. If this is the best I can manage while riding a bike, that story with the Flying Wallendas is definitely out. Ummmm, guys? How about if we just do the interview via e-mail?

After righting myself, I start back up the road. "You lost your water bottle when you fell," Landis says.

I look underneath my bike but I don't see it. Landis points down the road where the bottle is gaining speed as it rolls downhill toward a busy intersection. "Don't worry," Landis says, racing down toward the bottle. "I think I can get it."

This pretty much sums up the past year for Landis. Almost one year ago to the day, he had taken over the yellow jersey en route to his first-place finish in the Tour de France. And now here is one of the world's greatest cyclists, not only riding a bike with a sportswriter 5,000 miles away from his fellow pros in France but also fetching my frigging water bottle.

Of course, whether you see that as a horrible miscarriage of justice or his just desserts depends on whether you believe Landis took performance enhancers before Stage 17 last year.

Landis' 2006 Tour de France was so extraordinary, so compelling, he should have been silhouetted against a full moon with E.T. in his backpack. He showed up for the initial time trial nine seconds late, announced mid-Tour that he needed a hip replacement due to the same condition that eventually ended Bo Jackson's career, lost the yellow jersey when he bonked in the mountains on Stage 16, nearly recovered it the next day in Stage 17 with an epic alpine ride so powerful the peloton might as well have been delivering newspapers on their Sting-Rays, regained the jersey in the next stage and finally rode down the Champs Elysées to extend America's reign to eight years.

And then his world collapsed faster than a sportswriter unable to release his foot from the pedal.

Mere days after winning the Tour, Landis learned he had tested positive for an excessive ratio of testosterone to epitestosterone. Further testing revealed synthetic testosterone in the urine samples. He was kicked off his Phonak team and suspended from competitive cycling. When his initial explanations fell somewhat short of convincing, he became fodder for national jokes, including David Letterman's Top 10 Landis Excuses (No. 3, "Hulk no need excuse," and No. 2, "Frankly, I'd rather be a disgrace than a loser").

Landis vehemently denies he doped during the Tour and is fighting to clear his name and retain his title. He argued his case to a U.S. Anti-Doping Agency arbitration panel in May, mounted a vigorous, detailed "Wikipedia Defense" over the Internet and recently published his story in a very readable book, "Positively False: The Real Story of How I Won the Tour de France."

Essentially, his defense is that the French lab tests were seriously flawed. He makes a couple persuasive points. Sample identification numbers were written down wrong in several instances. Different standards at other labs would not have concluded he had a "positive" doping result. Naturally, the drug-testing agencies have a slightly different view, such as why there was any trace whatsoever of synthetic testosterone in his urine. (And that whole Greg LeMond thing wasn't so good.)

If the arbitration panel finds in Landis' favor, he will retain his title and return to racing. If he loses, he will have his title stripped away and face a two-year ban from cycling. Until then, he flies from city to city promoting his book and pleading his case … and also riding with a sportswriter who can't even stay upright on his bicycle.

"So," Landis says as we begin up the hill toward Magnolia, "what are they going to do about Barry Bonds?"

This unprompted question leads to a discussion about steroids in baseball and performance enhancers in sports in general. Landis says the Bonds' issue is different from doping in cycling because baseball didn't specifically ban steroids, while cycling did. "How can it be cheating if it isn't against the rules?" he asks of Bonds. He complains about how cycling is talking about banning oxygen chambers that simulate high altitude training, wondering where you draw the line on such matters and whether they'll start restricting how much you train. I find myself nodding a lot, partly in agreement but also probably because I'm hyperventilating.

"I never dreamed my name would be linked with Barry Bonds," Landis says with some degree of wonder.

Upon reaching a crest of the hill, we are greeted by a spectacular view of Elliott Bay and the Olympic mountain ranges. I am sweating and gasping for breath. My lungs need a fire engine. Landis is checking his e-mail or something on his iPhone while cycling with no hands.

How fast and powerfully a top cyclist can climb a steep hill is impressive enough.

What I find equally astounding is how fast they go down hills. As we descend back through Discovery Park, Landis leaves me far behind. I'm going as fast as I feel safe, but Landis is flying far ahead of me as if I were dragging an anchor. How fast would be go if he were actually racing?

This has been a terrible year for Landis. He estimates the doping scandal cost him between $5 million and $10 million in endorsements and other money, while his defense has cost $2 million. Worse, his father-in-law and close friend, David Witt, committed suicide. He says he hopes the Tour fallout wasn't a factor, "but I can't get it out of my head. When I win this thing, it will be for him. That guy was my best friend. He wanted me to win worse than anybody. He supported me when I wasn't making any money, and he always supported me. For him not to get to appreciate that I won, they're going to pay for that."

Not surprisingly, he doesn't have many good things to say about the drug-testing agencies.

"All I want out of this is the next time Dick Pound opens his mouth and says someone is guilty, the rest of the world says, 'We'll wait and see.'"

After a 90-minute ride through Magnolia and over to the University of Washington, we return downtown and roll through Pike Place Market. Landis took it very easy on me, allowing me to pretty much set the pace at 18-20 mph. His hotel is at the corner of Madison and Fourth, which requires a climb up a hill so steep it should have a base camp. Landis powers up the hill. I'm not that embarrassingly far behind, but the crucial difference is Landis not only takes the hill with ease, he could continue climbing to the summit of Mount Rainier if need be. Me, I'm so winded at the top that I can barely speak when I sit down to go over a few of his comments that I didn't have time to write down earlier because I was dying.

"The sad thing is every performance is questioned now," Landis says, acknowledging that might sound hypocritical. "You can't do something impressive because you were inspired or because they worked hard and believed they could do it, and they were smarter. Now every single reason other [than steroids] is gone. … They question everything, not just my performance but performances in every sport."

Well, yes. That's precisely the problem. We want to believe, to be inspired, to feel the sense of wonder that great athletic performances provoke. But we never can be sure these days. Which leaves us exactly where with Landis?

I normally believe the drug-testers, but this has been a difficult one for me since the very start. When Landis won the Tour last year, I was so inspired that I went out and rode a personal best around the south end of Lake Washington (I was also delighted that truck drivers would have a new name to call me besides Lance when they gave me the finger and shouted, "Get off the road … Floyd!") And something about the Stage 17 test result seemed curious to me when the results first were revealed last year. Why hadn't his A samples tested positive before that day? Why didn't they test positive afterward? Why such a huge one-day spike? Could injecting testosterone the day of a race really work quickly enough to be of any help at all that afternoon? I also was impressed by Landis when I met him. He is sharp, funny, engaging and unafraid to speak his mind.

So a large part of me wants to believe Landis, while a cynical part also worries about one day seeing a confessional book titled, "If I Did It." I guess I lean toward the view of Tim Van Mouwerik, a Seattle-area pharmacist who showed up at a Landis book-signing that drew hundreds of fans. "I like to believe he's innocent until proven guilty," he says. "And until the evidence is presented and the arbiter rules otherwise … "

All I know for certain is that I wish I didn't have to wonder.

I ask Landis how he responds when people tell him, "I want to believe you, but I just can't because it's so hard these days."

"I'd say, 'OK, fine. Don't believe me,'" he says. "But take a look at this stuff in the lab and tell me you'd like to be subjected to that type of testing. It's fine if you don't believe me, but just admit that they didn't prove that I doped. Nobody should be subjected to crappy work like that. If I did my job like those guys did theirs in the anti-doping agencies, no one would have ever heard of me. If I write down in my training diary that I rode for six hours yesterday to make it look good when I only rode for one, I wouldn't win any f------ races.

"I'll never convince every single person that I didn't do it, but I will convince them all that the system doesn't work, and it needs to be changed."

So read both sides of the case, and then believe him or not; the choice is yours. Meanwhile, Landis hopes to ride and win the Tour again -- "I would have been happy with one win, but now I have to make a point" -- but if that doesn't happen, he has his take on those who would take away his jersey.

"If I never ride another race, I won the Tour de France," he says. "And if they don't like it, f--- 'em."

Jim Caple is a senior writer for ESPN.com. He can be reached here. His Web site is at jimcaple.net, with more installments of "24 College Avenue." His new book with Steve Buckley, "The Best Boston Sports Arguments: The 100 Most Controversial, Debatable Questions for Die-Hard Boston Fans" is on sale now.