By the numbers: Why Paris-Roubaix is such a punishing race

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Paris-Roubaix is arguably the hardest one-day race in the world, a 257km slog over the rough cobbled farm roads of northern France that only the very strongest in the peloton can win. In Sunday’s 2017 edition, the ‘Hell of the North’ well and truly lived up to its moniker, despite great weather and favourable wind conditions for much of the day.

It was the fastest-ever edition of the race with an average speed of 45.204 km/h for the 5 hours 41 minutes it took eventual winner, Greg Van Avermaet (BMC) to complete the race. It was also full of the usual crashes, punctures, mechanical problems and aggressive racing that we’ve come to expect from Paris-Roubaix.

In the following article, former pro and Dig Deep Coaching co-founder Stephen Gallagher analyses the power data of riders in the 2017 Paris-Roubaix to find out just how hard this year’s edition of Hell of the North was, and what it took to post a strong result.

This article refers to the power outputs and power-to-weight ratios of the pros. To put these into context and see where the pros fit in relation to everyday riders, check out this table from Andy Coggan at the Training Peaks website.

The demands of Paris-Roubaix

Before we begin, here are some things to note about the conditions of Paris-Roubaix and how the pave can affect the power and force applied by the riders. Firstly, it is well noted that heavier, more muscular riders perform better at Roubaix than 60kg climbers. This is due to the flat nature of the race — riders need a high power output at Roubaix, rather than the high power-to-weight ratio that’s required in hillier races.

Not only do the bigger riders produce more power, they’re also better at absorbing the vibrations from the cobbles. To be at the front of the race, your body needs to be able to take this punishment better than your rivals’, and not let it affect your overall performance too much. Putting your body through 29 sectors and 55km of pave takes a major toll, as the rider’s ability to recover is reduced and the consistent impact from the cobbles reduces their ability to maintain a higher power/force time after time.

It’s also worth noting how power is produced and force is applied by the riders as they cross the flat cobbled sections at full speed. When we compare riding a 2-3 minute effort at a high intensity on a normal surface to the same effort on the cobbles of Roubaix, we see massive differences in how the force is applied. The cobbles require riders to engage more muscle groups and adapt their position on the bike. This leads to a greater energy expenditure on the cobbles compared to on regular bitumen roads.

Taking the above into account, the overall energy requirement to put out, say, 450W at 6 W/kg, for three minutes on a hard cobbled section like the Carrefour de l’Arbre is far greater than it would be on a relatively good surface. Not only does the body take more of an impact, but cranking out a consistent power is harder with the inability to find a good rhythm and with the wheels lacking a consistent surface to roll over.

Basically, racing on cobbles is damn hard.

Another big difference between Roubaix and other classics is that the start of the race is never a relaxed affair. If we look at Milan-San Remo, the Tour of Flanders and some of the other ‘Semi Classics’ which the riders take on early in the season, we can see that the first few hours are done at a relatively relaxed pace for the team leaders and those domestiques who are normally spared for the end of the race. This is not the case at Roubaix.

Team leaders need to be at the front, out of trouble and in the fight much earlier in the race and this leads to a lot more energy being expended before they reach the final 70-80km. There is no rest in this race and that means that incredible endurance, both aerobically and muscularly, are necessary for success in Roubaix.

We can see this in the data of André Greipel (Lotto Soudal) who was one of the most aggressive riders in the race and went on to finish in seventh place, 12 seconds down on the eventual winner. If we compare his first half of the race to the second half of the race we see exactly why this race is so hard.

First half: 2 hours 40 minutes 302W average 3.57 W/kg
Second half: 3 hours 326W average 3.86 W/kg

That’s a difference of only 0.29 W/kg between the first half and last half of the race.

If we compare this to a rider who fought a similar fight in the Tour of Flanders — Michael Valgren (Astana) who finished 11th — we see a drastic difference between the first and second half of the race:

First half: 3 hours 20 minutes 178W average 2.40 W/kg
Second half: 3 hours 297W average 4.01 W/kg

That’s a 1.61 W/kg difference between the first half and second half of the race.

The early effort put in by many of the main contenders again shows just how hard Paris-Roubaix is.

The hard start is also noticeable by the fact some riders hit their peak powers early in the race. Tim Declercq (Quick-Step Floors) was one of them. To keep his team leader Tom Boonen in a good position and out of trouble, Declercq hit many of his peak power figures in the first 50km of the race, including 10 minutes at an average of 390W (420W normalised*; 5.38 W/kg), after just 19km of racing.

The first hour of racing was done at a ferocious 50km/h with no early break let loose until just before the first cobbled sections at 96km into the race. Mickael Delage (FDJ) was in the three-up break and managed to stay out front over 11 cobbled sections in the 67km he was in the lead. During this 90-minute section, Delage had a normalised power of 345W (4.8 W/kg) and hit a max power of 1,048W early in that period. Delage lost contact with the leading group as they raced over the famous Trouée d’Arenberg.

We can see that in the early cobbled sections that Delage led, he was producing some pretty consistent power numbers:

Section Time Power W/kg
Viesly to Briastre 4:33 310W 4.3 W/kg
Vertain to Saint-Martin-sur-Écaillon 3:12 343W 4.76 W/kg
Verchain-Maugré to Quérénaing 2:27 371W 5.15 W/kg

The Race Blows Apart

As the riders entered the Trouée d’Arenberg the race was already starting to take shape. The peloton hit the five-star cobbled sector full gas with many riders fighting to maintain position. One of those was Ryan Mullen (Cannondale-Drapac) who produced 369W (4.67 W/kg) for the 3:41 it took him to pass over this iconic stretch of pave. He went on to finish 50th, 9:30 down on Van Avermaet.

Peter Sagan made his first major move at the end of cobble sector 17: Hornaing to Wandignies. André Greipel was in the main group at the time and found himself with Boonen as they chased Sagan who had a few seconds’ advantage as he exited this section. Greipel passed over the Hornaing to Wandignies sector in 5:08 at 350W (4.14 W/kg). In the 10km that followed, the riders tackled two more sectors and Greipel could be seen at the front of the chase group, forcing the pace to keep the gap down to the Sagan group and maintain his place at the head of the race.

For the 14 minutes it took to cover this 10km stretch, Greipel averaged 362W (405W normalised; 4.79 W/kg) and hit a max of 1,352W (16 W/kg).

Fight for the Finish

The race’s finale saw many splits at the front, with groups fragmenting and re-merging as they passed over the last sections of cobbles. Of those main aggressors was Daniel Oss (BMC) who paved the way for an eventual victory by his team leader Greg Van Avermaet. One of the other teams well represented at the front was Lotto Soudal with both Greipel and Nikolas Maes, both of whom finish in the main chase group, 12 seconds down on the winner.

Maes was riding the cobbled section of Auchy-lez-Orchies to Bersée at 360W (4.74 W/kg) for the 4:42 it took to get across. He produced a similar effort on the Pont-Thibaut to Ennevelin when he produced 336W (4.42 W/kg), all of this after 220 bone-rattling kilometres on the harsh roads of northern France.

The Carrefour de l’Arbre cobbled section has played a big part in deciding the winner of Roubaix on many occasions, as it comes with only 17km left to the finish. Maes was again in the group chasing the leading five riders at this point and it was on this sector that many contenders fall apart after having burnt many matches over the previous five-and-a-half hours of racing. On the Carrefour de l’Arbre Nikolas produced 355W (4.67 W/kg) for 3:26.

As the riders approached the iconic Roubaix Velodrome the sense of achievement must have been profound for all of those that manged to complete the race in one piece. Everyone is aware of Greipel’s sprinting prowess and he was to put this to good use on the velodrome. In the last 28 seconds to the line the German national champion produced an average of 1,035W (12.24 W/kg) and 58.8 km/h. In this section he hit an eye-watering max of 1,533W (18.14 W/kg) and 61.4 km/h. And remember, this is after 257km and 5 hours 40 minutes racing.

The 2017 edition of Paris-Roubaix will go down as the fastest-ever edition of the race but the effort and energy needed to complete this race is more than what can be shown by speed and power data. The unforgiving pave, the dust, the crashes, the mechanicals and the aggressive racing give Paris-Roubaix mythical status within the world of cycling. Just finishing the race is hard enough, let alone posting a good result.

*To understand what normalised power is and how it differs from average power, this explanation at Training Peaks is worth reading. In short: normalised power “is an attempt to better quantify the physiological ‘cost’ of the harder ‘feel’ of the variable effort.”
The graphics in this post appear courtesy of VeloViewer and Philipp Diegner.


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