The first week of the Tour often means watching sprints and waiting around for something (preferably non-violent) to happen — tedium that is only occasionally punctuated by short, stabby climbs where the top guys compete for a second or three. But this week the Tour is throwing a bit more meat to the hungry wolves.

On Sunday, riders will race to Roubaix in the far north of France, and tackle the fearsome cobblestone sectors of the classic Paris-Roubaix race. On the cobbles, we aren’t talking little gains and losses, we are talking about the potential to completely remake the race.

It’s not often you can circle a stage from the first week of the Tour de France and say that something big is going to happen. Sunday is one of those days.

Wait, cobblestones?

Cobblestone roads, ancient and new, are found throughout Europe, but only in northern France are they a tourist attraction thanks to cycling. But Sunday’s trip to the Départment du Nord is a bit like a pan-American event swinging by West Virginia Coal Country: Cool in a way, if not anything like your typical tourist route.

Culturally, the area around Lille, of which Roubaix is a suburb, is known for being a bit forgotten. It was literally cut off from Paris after World War I leveled everything in its path.

The nickname for Paris-Roubaix is “the Hell of the North,” which comes from the devastation experienced on the battlefields of the Somme. From Valenciennes and westward to the Atlantic is where village names start to sound a little odd, and Dutch can be heard in the markets. The region’s backwardness was at times a source of shame, so much so that after World War II local mayors started to pave over their outmoded cobblestone streets as quickly as they could. Until cycling intervened.

Paris-Roubaix dates back to 1892, and is considered one of the hardest days on the cycling calendar despite being relatively flat. Everyone from the race organizers, to fans, to some of the riders themselves began to speak up on behalf of preserving the old cobbled paths, and even searched out additional routes. The signature sector, the Arenberg Trench, came into the race at the suggestion of rider Jean Stablinski, who had previously worked in the coal mine that ran beneath it.

And as of 2018, the race is as great as ever.

Thanks to the spectacle, the Tour de France has often incorporated portions of the Paris-Roubaix course into an early stage. The wisdom of doing so is a subject of great debate, and the Tour’s interest in cobbles has swung over the years. Not only is riding on cobbles hard, it’s also treacherous.

Crashes happen frequently. Bikes break and riders lose chunks of time waiting for new ones. No less an authority than French legend Bernard Hinault has called the idea “bullshit.” But the Cobbled Classics are in vogue, and the discipline of riding on cobbles is a big enough attraction for the Tour to use them as the setting for some excellent early intrigue.

Why is riding on cobblestones so hard?

Including cobblestone sectors from Paris-Roubaix in the Tour is a huge test for pretty much everyone involved. Maybe the support vehicles are sufficiently practiced in their jobs here, but everyone else will be under serious pressure Sunday.

The pressure starts with the mechanics of riding on cobblestones. To counteract the effect of their wheels bounding every which way, riders need to push an ungodly amount of wattage into their pedals, because every bounce off a stone (roughly one per 0.005 seconds) translates into arrested momentum. If you don’t have any rough cobbles in your neighborhood, try pedaling in sand. It feels about the same.

Larger riders create more force and more momentum than smaller ones, so the lightweight climbers who are expected to compete for the yellow jersey are at a big disadvantage. Heck, larger riders are barely even selected to start the Tour. When cobbles are thrown into the course, however, all that changes.

This is the day that the big guys have been waiting for. And for the smaller guys, Sunday will be a matter of hanging on for dear life.

Unlike the lumpy stones in Belgium featured in the Tour of Flanders mega-classic, the cobbles in France are completely unforgiving. They are jagged, unkempt, and unruly. The roads themselves feature high crowns in the middle and sloping sides that, at high speed, try desperately to steer your momentum into a ditch. Riders cling desperately to that crown, often mere inches wide, until it disappears, leaving even the top guys hanging on for their proverbial lives.

The main skill for riding here at the ridiculous speeds of the pro peloton is fearlessness, followed by incredible bike handling, followed by more fearlessness. These are traits you can develop with enough practice, but the Tour de France mountain men have often not practiced nearly enough.

Oh, and factor in bad weather — as is often the case in the boggy northern France climate — and cobbles become a nightmare for even the very best bike handlers. Here’s Italian Francesco Moser losing the crown of the road, sliding sideways and keeling over in the 1985 Paris-Roubaix:

Moser had won three previous editions of the race. In Paris-Roubaix, nobody is spared for long.

So how will cobbles affect the Tour?

Cobbles are modular: they come in sectors from 500 to 3000 meters in length, with smooth, flat roads in between where riders can recover and regroup. If disaster doesn’t happen and a rider remains upright, then the cobbles will still eat up a lot of energy he was hoping to conserve. The number of sectors, along with their length and difficulty, determine how many matches get burnt on the day. The winner will be the rider who can handle the stones as efficiently as possible so that he has something left in his tank for a sprint finish.

One thing is certain: There will be time gaps all over the road. The cobbles themselves, even without any crashes, tend to spread people out, and that’s before you consider how often bad luck occurs. Here’s how cobbles significantly affected the Tour in the past:

2014: Vincenzo Nibali goes for broke

Possibly the most memorable cobbles stage in Tour history, Vincenzo Nibali basically won the entire Tour here. Nibali is a lot of things — mostly he’s a great bike handler, and mentally stronger than anyone I can remember — but he’s not the world’s best climber or time triallist. So when he blew out his three-second lead to multiple minutes over the nine cobbles sectors (15.4 kilometers total), his (injury-depleted) rivals had no answer.

2010: Frank Schleck upsets Alberto Contador

After their tepid reintroduction in 2004, the cobbles returned in force for the 2010 race. Fabian Cancellara, the star of that year’s classics season, shepherded Andy Schleck to safety while chaos reigned in their wake. A crash on the first sector split the peloton, and Schleck was able to put a minute into Alberto Contador, who was favored over his fragile Luxembourger rival.

Contador would go on to win the Tour by attacking Schleck during a chain malfunction, only for his title to be vacated almost two years later by the CAS, long after fans had gotten sick of everyone involved.

1985: Last of the great battles (for a while)

Henri Manders and Teun van Vliet pounded away over 10.5 kilometers of cobbles in ten sectors, with a massive 20-minute advantage at one point, only to see it whittled away to mere seconds. Manders hung on to win with the chasers just 11 seconds back. The overall favorites were guys like Bernard Hinault, a former Paris-Roubaix winner, and Greg LeMond, who had just finished on the podium of Paris-Roubaix that spring. Those were different times, when the stars of the Tour were the stars in every discipline of cycling.

After this stage, cobbles were absent from the Tour for nearly two decades.

1983: A absolute brute

With 28 kilometers of cobbles, the 1983 stage was one of the toughest ever. The Colombia team dropped tens of minutes on the road, and Robert Millar of Scotland crashed and dumped 17 minutes. Information is a bit scant, but the danger factor definitely got people’s attention, and two years later the Tour was done with the idea of such madness in the middle of the Tour.

1980: Bernard Hinault is fueled by hate

On stage 6, the peloton rode from Lille to Compiègne, the reverse order of Paris-Roubaix, in deplorable conditions. Bernard Hinault — who would go on to race Paris-Roubaix a year later, fall seven times, and win before anointing the race “bullshit” — took the stage by more than two minutes.

There is no predicting what will happen next

We are deep into the era of rider specialization, but we have also seen a few rounds of cobbles in the Tour recently, so teams should have learned the lessons needed to prepare wispy men like Chris Froome and Nairo Quintana for what’s to come. I don’t think the race will be decided by incompetence, but even the stars of Paris-Roubaix will tell you that the key to success is simply to not have bad luck.

Someone will have bad luck. If there’s one thing to expect on cobbles, it’s that. Splits will happen, and it will be incredible drama all the way through. And the riders will be in hell.