When Max Levchin was 10 years old and growing up in Communist Ukraine in the mid-1980s, his parents saved up to buy him a junior-size road bike, a rare luxury, and his mother, a cycling enthusiast, taught him how to ride. His family happened to live in an apartment complex that stood behind Kiev's only open-air cycling track. At night, Levchin would sneak into the closed facility, pedaling around the oval, counting each completed lap in his head as he tapped out a steady rhythm. In the darkness of the velodrome, the only sound he heard was the whirring of his chain spinning the cogs on the back wheel of his bicycle.

Nearly three decades later, Levchin still rides, not in a velodrome, but in the California hills. Numbers continue to speed rhythmically through his mind, powering the engineering genius of his work and the data-driven cyclist he has become, logging between 200 and 300 miles a week, often over the steepest hills he can find. And while his state-of-the-art carbon-fiber road bike is a world away from the steel racer he’d ridden as a boy, Levchin's passion for cycling has only intensified. Every day, the 39-year-old entrepreneur — who has multiple hits behind him and more startups now in early stages — competes only against himself.

I have no business riding with Max Levchin.

This thought flashes through my mind as I watch him pedal away from me. Having pushed off at 7 a.m., we're not long into our ride on a cold mid-November morning, and he's already dropped me on the first climb, Camino Alto. It's a quiet, leafy ascent in Mill Valley, north of Levchin's adopted hometown of San Francisco. Camino is not a particularly hard climb, but he's pushing 400 watts and I'm pushing myself into oxygen debt. Eventually I crest the summit and find him waiting on the side of the road. He’s standing over his bike, tapping the display of his cycling computer. It looks like he’s not even breathing.

A pattern emerges. We hit a climb, Levchin blitzes up the hill, I do my best to chase him, and he soars out of view. He waits at the top, I roll up, and we bomb the descent. We match pace on the flats until the next climb, and the cycle repeats itself. Perhaps the hardest thing about doing this ride, known locally as Paradise Loop, is not that Levchin is out-climbing me, which he is, but that he’s so nice about it. Over the course of our ride, he takes the time to tell me about the local roads, all of which he knows intimately. He points out potentially wet or dangerous grates and manhole covers. If he were a jerk and this good on the bike, I could easily dislike him, but he’s not. He’s just very fit and surprisingly laid-back for a star of Silicon Valley. It’s hard to not like him.

Rediscovering a sense of order

Two days before our ride, Levchin — the serial entrepreneur who cofounded PayPal and the game maker Slide, and joined Yahoo's board at the behest of CEO Marissa Mayer — agrees to meet me at his office in downtown San Francisco. There he works on one of his latest startups, Affirm, which aims “to remake consumer finance from the ground up.” It’s a casual, open-space office. Levchin is wearing sneakers, jeans, and T-shirt, and he greets me with a bar of dark chocolate and iced coffee. As we sit down to chat, he opens by saying, “I’m completely obsessed with cycling. It’s the only sport I follow.” That means keeping close tabs on everything from one-day classics like Paris-Roubaix and track racing, to cyclocross and the grand tours such as the Tour de France.

That, thankfully, puts us on slightly more equal footing. Technology is not my beat, but as a journalist I have been to the Tour and Milan-Sanremo and the Tour of California and other world-class bike races, and I've pedaled a road bike since I was a teen, too. Over the years, Levchin and I have both done our share of racing in the amateur ranks, but three years ago he crashed hard at 40 mph. This “pretty permanently” injured his right hip and more or less put an end to his racing; about the same time, I wiped out on a mountain bike, breaking bones in my left leg and ankle. I, too, am pretty permanently injured, thanks to an initial misdiagnosis that, in the end, had me wearing a cast and confined to a couch for nearly a year. Bouncing back from those crashes is something we’re both tackling, though his grueling daily regimen is a tough one to match.

PayPal cofounders Peter Thiel and Max Levchin on February 15, 2002, seconds after the stock market close on their IPO day. Said Levchin: "Peter and I are crowned — the party is really going to start now." He'd made his first fortune. levchin.com

Levchin moved to the Bay Area in the late 1990s, and while he was working at PayPal, he didn’t ride a bike at all. After PayPal, he was “bored” and gained a little weight. His girlfriend, and now wife, Nellie, said to him, “You have a beautiful bike sitting in the garage. Why don’t you ride it? It’ll give you a sense of order.”

But it was a few months before he decided he was ready to take up cycling again seriously. He used to be good at it, he says, and now had to deal with being “fat and slow on the bike.” He didn’t want the frustration of not being able to fly up hills.

As I would learn, Levchin doesn’t care for moving slow. He tackles climbs just as he appears to do business: deliberately and efficiently.

Levchin says he became "readdicted" to cycling after attending some CompuTrainer classes, in which you set your bike up on an indoor turbo trainer and do high-intensity interval workouts. “I ran my Vo2 max and was like, ‘Oh, I’m still pretty good — I can still push 300 watts without breaking too much sweat,” he says. “I was probably stronger than most people in the CompuTrainer group, so I thought I might as well get back on the road.”

"Every couple of years I threaten to get back into racing, but Affirm has taken up a lot of time that I’d normally spend training," he says. "To be competitive, you need to ride 15 hours a week, at least, and I'm not really there anymore, but I still manage 10 to 12 hours consistently, some weeks more. My primary goal right now is to still be the strongest in my pack," he says with a little smile, "though sometimes that might involve editing the pack."

The millionaire who goes to bed hungry

Throughout the 2000s, Levchin pursued cycling while he was building Slide and helping with the launch of Yelp. Then, Google bought Slide, in 2010, for an estimated $228 million. The following year, Levchin came up with a new project: win bike races.

He trimmed down, hitting a low of 153, taking on the lean frame and low body weight of most competitive cyclists. His threshold power, a significant predictor of endurance performance ability, was between 385 and 390, and he could “put real hurt on people.”

Levchin became so thin that one day his wife said to him, “Look, a couple more pounds, and I’m going to look for an alternative husband. There’s not a lot of you left.”

“She threatened to take photos,” Levchin recalls, “because she could count my ribs from the back. I said, ‘All right, just give me a year. I wanna race.’”

During that time Levchin often went to bed hungry in an effort to get leaner. But it wasn’t as simple as riding a bike and eating carefully, because there were things like running a company and leading all-hands meetings. He had to have enough sugar to function. “My goal for about a year was to be the best cyclist I could be, and I worked hard at it,” he recalls, “and I was quite good.”

Today, Levchin weighs 165 pounds, “and that’s if I have a light breakfast,” he says only half-jokingly. He estimates that his threshold now is 365, or about 5% lower than when he was racing. “It used to be like, ‘Hey, there’s a fun hill — I’ll show you how it’s done.’ Now it’s like, ‘Oh man, I’m going to have to really work it.’”

Data as truth

For all his passion for two wheels, it isn’t just pedaling Levchin loves. He also thrives on data and information. It’s helped make him who he is, quite literally. (As PayPal's chief technology officer, he revolutionized the payments system and developed breakthrough antifraud technology.) After hanging out with Levchin, even for a few hours, you get the impression that no matter what he’s doing, he can’t go long without some sort of numbers to process.

Today, cyclists like Levchin have loads of performance information at their fingertips, and quantifying training intensity and recovery is much easier to do. Many amateur athletes, and almost all the pros, have power meters attached to their handlebars, as does Levchin. One of his favorite tools that he syncs with his power meter is Strava. Used by cyclists and other endurance athletes around the world, the Strava app allows you to record your speed, elevation gain, calories burned, power output, heart rate, and more, and then share it online and compare notes with others. A popular feature on Strava is the KOM, or king of the mountain. When you climb a hill, or a “segment” in Stravaspeak, faster than everyone else, you become the king of that climb. That is, until someone pedals up faster and knocks you off.

Strava’s headquarters are in San Francisco, not far from where Levchin lives and works. The day Strava launched in 2009, Levchin signed up as a paid “premium” member. He encouraged his friends to start paying for the service too. “I was like, ‘You don’t want this thing to shut down,” he recalls. “I’m a big fan of products where I’m passionate about the experience, so I’m happy to pay for it. I think Strava is doing fine now.” (That’s true: In October, Strava raised $18.5 million in Series D funding. It also hired venture capitalist Michael Moritz of Sequoia Capital as an adviser.) For data-driven athletes like Levchin, Strava is a must-have.

"My No. 1 competitor is me,” he says. “In the end, the trick of convincing yourself that you’re still good because your buddies are having a bad day and you’re killing them only goes so far. Strava is the source of truth, where you upload your ride and say, ‘Hey, my power up this hill was 5% less than it was last year, when I set my personal record. My heart rate is a bit higher.’ There’s no one to blame but you.

“Then you say, ‘What’s going on here? Oh, you’re trucking around five more pounds, and you’re not training as hard.’ So Strava is a good way to keep yourself completely honest. It’s also a good way to compare notes with other riders. It creates a ladder for me to climb. For most segments on Strava, I know I’m not in the top 10, but I’m frequently in the top 10% or 20%, and that’s a meaningfully high level.”

With the most popular KOMs on Strava, he knows the top riders are pros, but still he’d like to get as close to them as possible.

The reptilian brain

What’s most compelling about cycling for Levchin is that it comes down to riding through the pain. “There’s always a moment where you’re like, ‘I can’t do it anymore,’ but it’s never when you’re cresting — it’s when you’re halfway up a climb,” he says. “When your tongue is hanging out on the handlebar and you’ve still got another five k to go. You just have to fire that extra gear, or climb off, which is sort of pathetic.”

That skill is mirrored in successful entrepreneurs, he says. "When I'm in the middle of a really hard ride, it's a bit like starting a company," he says. "Am I going to slow down, or am I gonna go all in? And you just grind. On the bike, I'm no [Tour de France champion] Chris Froome, but I work very hard. I'm willing to suffer. I ride every day, no matter what."

Still, even Levchin admits that in both entrepreneurship and cycling, sometimes you have to know when to give up. “In a bike race, if you know you’re not going to bridge to the front group, you don’t want to burn yourself, because you know there’s another race tomorrow,” he says. “In entrepreneurship it’s the same thing: You can spend five years trying to find an elusive market that doesn’t exist. The parallels are fairly frequent, but the one that appeals to me the most is this getting through the barrier of ‘I just can’t do it anymore.’ That’s just not an option. It’s very true in bike races, and it’s very much true in entrepreneurship.

“The one thing that happens when you’re at the limit on the bike is that you get this diminished reptilian brain,” he tells me. “There’s no room for neocortex, there’s no room for middle-brain activity. It’s like [makes heavy-panting sounds] — Make it stop! And the only way to make it stop is to get to the finish line.”

Whereas some people might burn out with so much data passing through their reptilian brains, Levchin can’t seem to get enough. And that can be a problem: All the data he picks up feeds into his tendency to over-train, and it’s hard for him not to work hard. He even gets annoyed whenever he has to ride slow.

“My No. 1 enemy is the power meter,” he says. “If the number has not cracked 300 [watts] I am not OK with that.”

He recalls a recent workout at home on his indoor trainer. It was supposed to be a recovery workout during which he’d go easy, give his body active rest, and spin out lactic acid. But after warming up he found himself looking at his power meter, which read 190 watts. He decided that was pathetic, so he pushed harder and was soon at 250 watts. Not long after he was hammering at 300 watts. He literally could not pedal easy.

“It’s very easy to be very focused on one thing,” Levchin tells me. “If you’re focused on being the best cyclist you can be, it’s easy to deprive yourself of conversation, food, wine, whatever it is that interferes with being the best cyclist, because you need your eight hours of sleep and your carefully measured calories.

“When you’re training and running a company and you’re trying to be a good family man and have friends, inevitably you have to make a decision where you say, ‘Well, it’s stupid not go to this great dinner party, because I’ll see all my friends and I’ll have a great meal and it will be fun, and yeah, I’ll stay up late and I’ll still ride in the morning, but I’ll feel crappy and be two pounds heavier than I would like to be, and probably slightly hung-over.”

Levchin used to ride every other day outdoors and the rest on the indoor trainer. These days, he typically does five days on the trainer and “sneaks out” for longer rides on the weekend. That, in part, is because he and his wife, Nellie, now have two kids.

“They’re a lot of fun,” he says, “and they need me and I need them. Today, for instance, it was very tempting to just go out and ride, but I wanted to be with them, so I just banged out an hour on the trainer doing intervals.”

Riding with Levchin reveals his intensity. When he wasn’t pushing it on the climbs, we sprinted for town signs. When a magnet used for his computer’s sensor became dislodged from his chainring, Levchin, the meticulous engineer, spent several intense minutes to try to fix it on the side of the road, as if he feared he might miss the opportunity to capture some ride data.

Coming full circle

Our three-hour ride ends at one his favorite coffee shops. Levchin checks his computer to see how far he’s ridden, and checks his phone to see who has been texting him. He’s got a little more time to ride, he realizes, before he and Nellie take their kids to a party that afternoon.

I’m cooked, and I’m content to sit in the sun and sip espresso. Sure enough, Levchin tells me he’s going to take a quick spin up and over a nearby climb and that he’ll be back shortly. I watch him reset his computer for his next workout, and off he goes.

Inside 30 minutes Levchin returns, with the extra climbing workout done.

As we head back to San Francisco, over the Golden Gate Bridge, he’s already talking about his next ride.

“For someone as competitive as I am — foolishly competitive or correctly competitive — it’s sometimes hard to reconcile having a family life and a great experience with my friends and a nice meal with a great glass of wine, and the prioritization is pretty hard,” he says.

“I’m getting better about knowing what’s important, but in the morning I still want to be the fastest guy up the hill.”