Technical FAQ: Tires and pressures at the 2021 Paris-Roubaix

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Dear Lennard,
My eyes were bugging out reading your test on rolling resistance of Paris-Roubaix tires. As a devoted tubular rider, I was blown away that the clinchers smoked the tubulars. That was a big surprise. I guess it shows I’m not as sensitive as I thought. Apparently, I can’t feel 10-watt friction differences — or even twice that — wow! Instead, I thought I was feeling the opposite. I guess your tests of chain friction the last few years already showed me that I couldn’t feel 5-watt differences, so maybe this shouldn’t surprise me. I still love the feel of nice tubulars. You can’t take that away from me, LZ!

Do you know which tires actually were used in Paris-Roubaix this year and at what pressure? Is it still a race for tubulars?
— Will

Dear Will,
As our test foreshadowed, and in an almost-certain sign of things to come, both the men’s and women’s races were won on tubeless clinchers. Yes, some teams were on tubulars, but far from being ubiquitous as in the past, tubulars were probably in the minority.

Super cool IMHO and indicating that science is real, the finish order of the three men and of the first two women was the same relative finish order of their respective tires in our rolling-resistance test. (The third-place woman was on the same tires as the winner.)

Sonny Colbrelli won this awesome, muddy, October Paris-Roubaix on tubeless Continental Grand Prix GP5000S TR tires mounted to deep-section Vision Metron carbon clincher wheels “in 32mm and pressure in between 3 to 4 bars [43.5 – 58 PSI],” according to Continental. This was the tire that took second place in our test of rolling resistance of tires for this race, except we tested 28mm (and 25mm), not 32mm.

We included no 32mm tires in our test. In the three cases where we tested two sizes of the same tire, the bigger tire always was faster, so there is reason to believe that the 32mm GP5000S TR might be faster on cobbles than the 28mm or 25mm ones we tested. Certainly, Colbrelli would have had better traction on the slick cobbles with the 5mm-bigger tire, would have been bounced around less (thus saving more energy), and would have protected his rims better.

At the pressure where their rolling friction was at a minimum, a pair of Colbrelli’s tires in 28mm consumes 34 watts of power to go 35kph on a simulated cobblestone surface with a 40kg load on each tire. The tires of the second-place rider required 41.6 watts and those of the third-place rider required 53 watts. Those are big differences. Imagine putting out 19 watts and 8 watts more than your breakaway companions for 160 miles and then trying to beat them in the sprint. Even if that power difference only occurs on the 34 miles of cobblestones, that’s still a lot more work the third-place rider did than the other two.

Yes, the tires would have required less power to roll on the asphalt sections than on the cobbles, but previous tests we have run at Wheel Energy Oy have shown that, while the magnitude of energy loss would have been less, the relative order of fastest to slowest tire would have remained the same. For instance, Filippo Ganna (Ineos Grenadiers) rode Conti GP5000S TR tires when he won the individual time trial at the road World Championships a couple of weeks before Colbrelli won Paris-Roubaix on a fatter version of them. Also, factor in that the peloton generally rides the Hell of the North’s asphalt sections considerably faster than our 35kph test speed. The faster a tire rolls, the more power it demands, so it’s possible that the power cost would not have been enormously lower on the asphalt sections than on the cobbled sections. Added up over the race, I believe the wattage difference the three riders experienced rolling their tires for six hours could have meant the fatigue difference that decided the final sprint.

Although Paris-Roubaix has been won previously a time or two on clinchers, this was the first time I know that it had been won on tubeless ones. Otherwise, every edition has been won on tubulars.

Our tests found the lowest rolling resistance on simulated cobblestones at 35kph with a 40kg load on the 28mm tubeless GP5000S was at 4 bars; Colbrelli’s pressure range intersects it.

Gianni Moscon of Ineos had looked on his way to a solo victory while riding on the same Conti tubeless tires as Colbrelli was, and leading by 1:15 when he flatted with 25km to go (did he burp the tire?). That flat followed by a crash derailed his effort. He slid out on a straightaway — not much different from hundreds of other spots on the course that he had already successfully negotiated. Moscon said that the spare bike he was given after his puncture had different tire pressure than what he had been riding on and felt different on the cobbles.

The 10th-place rider and Colbrelli’s teammate, Heinrich Haussler, rode the same 32mm tubeless GP5000S tires, except at 2.6 and 2.7 bar (38 and 39 PSI)! In our test of a 28mm version, pressure that low would have demanded 6-8 watts more per tire than at 4 bar. That said, the low point of rolling resistance for the bigger 32mm tire might be at lower pressure.

Also read: Paris-Roubaix redux — Heinrich Haussler on ‘the hardest race of my life’

Haussler had not planned to go that low, but he rode most of the cobbles on a spare bike following a mechanical. Those pressures were measured in its tires after the finish. He weighs 71kg and with his bike probably 78kg. So, his rear tire probably had more than the 40kg test load on it and his front less.

Some people have written to me that those tires don’t work on some rims. Continental replied that “the previous GP5000TL was not allowed on hookless rims (Zipp, Enve) and those were the only brands where it was not possible – with the new one it is possible with max. pressure 5bar / 73PSI.” The new GP5000S TR replaces the 3-ply casing of the GP5000TL with a 2-ply casing, saving 50 grams (on the 25C size), and is claimed by Continental to be “20 percent faster” and have tougher sidewalls to boot.

Also on tubeless clinchers, Lizzie Deignan won the inaugural women’s Paris-Roubaix the prior day on stock Pirelli P Zero TLRs in 30mm, the same tire that was fifth-fastest in our test. She was riding around 2.7 bar (39 PSI) with a full tubeless-ready setup with inserts, according to Davide Valsecchi, sport marketing manager for Pirelli’s Cycling Division.

Our test predicted it would take 8-11 watts per tire more to roll a P Zero TLR on cobblestones at 2.7 bar than at 4 bar, where it was fastest. However, that test was with 40kg on the tire, and there is no way that Deignan had 40kg (88 pounds) on each tire—I would believe her tires were each averaging 29kg (64 pounds) on board. Deignan’s teammate, Elisa Longo Borghini, rode those same tires to third place, 1:47 behind.

Like Deignan, some of the riders on tubeless tires had foam inserts in them to prevent burping and to pad sharp strikes on cobblestone edges and minimize rim and tire damage at low pressures. Since we didn’t run our test with tubeless inserts installed, I can’t say how much energy would have been absorbed by the inserts. Some tubeless inserts are low and flat, and some take up much of the volume of the tire but are pushed lower by the air pressure above them. Perhaps inserts don’t absorb energy except at pressures low enough and impacts hard enough to compress the tire down to them. Of course, you DO want them to absorb energy from sharp impacts!

Paris-Roubaix is often decided based on who does not puncture, break wheels, or crash, and tubulars have always held the advantage in this race because tubulars resist punctures and pinch flats better than clinchers, tubular rims are less vulnerable to impact damage than clincher rims, and the lower pressures tubulars can be ridden at provide better traction and reduce crash likelihood. However, with inserts inside, tubeless tires arguably exceed tubulars in those same categories of reliability in this race so brutal on equipment and bodies.

Pirelli’s men’s teams (AG2R-Citroën, BikeExchange and Trek-Segafredo teams) “were riding a mix of solutions, mainly: P ZERO Race TLR 700x30c with different inserts based on the inner width of the rims and P ZERO Velo 30mm tubulars. When it comes to pressures of course it really depends on each rider, but we can say that for men the range was 3.5-5 bar (51-73 PSI) for the tubeless-ready and 4.5-5.5 bar (65-80 PSI) for the tubulars,” said Valsecchi, who added, “We did some tests with the teams ahead of the race and together we set a baseline. The pressure was then adjusted according to the poor weather. AG2R-Citroën was the only team that got the chance to test in similar (maybe worse?) conditions in late January.” Our test found the Pirelli tubulars to roll fastest on cobbles at 5.5 PSI and the tubeless Pirellis to be fastest at 4 PSI, so those teams used near those marks.

Sharing the men’s podium with Colbrelli and his tubeless Contis, Lotto-Soudal’s Florian Vermeersch (second place) and Alpecin-Fenix’s Mathieu Van der Poel (3rd place) both rode Vittoria Corsa Control 2.0 graphene tires. However, Vermeersch was on tubeless clinchers with inserts, while Van der Poel was on tubulars. The same sizes and models as tires in our test, Vermeersch’s Corsa Control 2.0 TLR tubeless clinchers were 28mm, and Van der Poel’s Corsa Control 2.0 tubulars were 30mm; tire pressures are secret. Again, Van der Poel would have been putting out on the order of 19 watts and 8 watts more than Colbrelli and Vermeersch, respectively, and their finish order was the same as that of their tires in our rolling-friction test. Was van der Poel’s dusting in a sprint that we otherwise might have predicted him to win indicative of those extra energy costs in fatigue over six hours? What might have happened had he ridden the same tires as Vermeersch, which were also available to his team? All three riders rode aero bikes and aero helmets, so there was no power cost in aerodynamic drag to tally up over the race.

In seventh place, on similar but not identical tires to van der Poel, Jumbo-Visma’s Wout van Aert rode 30mm Dugast tubulars with the same Vittoria Corsa Control 2.0 4C Graphene tread glued to the casing as the Vittorias on the podium. Marianna Vos (also Jumbo-Visma) rode those same 30mm Dugast-casing/Vittoria-tread tubulars to second place the day before. Inquiring minds wonder if Vos might have closed that 1:17 gap if her tires had not required 12 watts more power (or something similar) over the entire 116km than Deignan’s tires to go the same speed, as our test showed. While we didn’t test this exact tire, and the Dugast casing may be a bit more supple than Vittoria’s, it’s the same basic construction method and is still a tubular with the same energy loss at the glue joint with the rim and the cotton base tape. I doubt that its rolling resistance is significantly different from the Vittoria tubular.

Specialized’s 28mm Turbo Cotton clincher lined with a latex inner tube won our Paris-Roubaix-simulating rolling-resistance test and was the tire used by Deceuninck-Quick-Step, the team that won the 2021 UCI World Team Ranking and was a heavy favorite to win Paris-Roubaix. Missing the podium for the first time in ten years, its best-placed rider was arguably the strongest man in the race, Yves Lampaert. He won the sprint for 5th from Van Aert’s group after three punctures (putting a question mark on the idea of non-tubeless clinchers on big cobblestones). Can Specialized transform that fast tire to tubeless by April? DQS pumped the inner tubes inside their Turbo Cotton clincher up to 4.2–4.6 bar (61-67 PSI). However, our test showed 5 bar (73 PSI) to be where that tire’s rolling-resistance is at a minimum on cobblestones, which would have greatly reduced the potential for pinch flats and cracked rim walls.

Bora-Hansgrohe also uses Specialized tires, and Peter Sagan was its highest-placed rider; he crashed and finished 57th. Even though Bora-Hansgrohe reconned the course on Turbo Cotton clinchers, it raced on 30mm Turbo Cotton tubulars, which tied Deignan’s Pirelli P Zero TLR tubeless clinchers for 5th-fastest in our test. BHT’s tubulars were pumped to 4.2–4.7 bar (61-68 PSI), according to Specialized, while our test showed them to be fastest at 5.0–5.5 bar (72-80 PSI).

The eighth and ninth placed riders, Tom Van Asbroeck and Guillaume Bovin (who crashed out of the winning break at 20K to go) from Israel Start-Up Nation, probably were on the 30mm Maxxis Velocita tubulars that came in 7th in our test (the second-fastest tubular after the Specialized Turbo Cotton tubular). I haven’t been able to get an answer from Maxxis about what tires and what pressures they used. The other rider in the top ten, sixth-place Christophe LaPorte of Cofidis, would have been on Michelins, which we did not test.

The VeloNews rolling resistance test was clearly awesome for understanding Paris-Roubaix better. For something more applicable to riding you might do, look for the upcoming article I wrote on testing the rolling resistance of popular gravel tires, and for that test I’m investigating the rolling resistance difference between butyl, latex, and polyurethane inner tubes.
― Lennard

Lennard Zinn, our longtime technical writer, joined VeloNews in 1987. He is also a custom frame builder (www.zinncycles.com) and purveyor of non-custom huge bikes (bikeclydesdale.com), a former U.S. national team rider, co-author of “The Haywire Heart,” and author of many bicycle books including “Zinn and the Art of Road Bike Maintenance,” “DVD, as well as “Zinn and the Art of Triathlon Bikes” and “Zinn’s Cycling Primer: Maintenance Tips and Skill Building for Cyclists.” He holds a bachelor’s in physics from Colorado College.

Follow @lennardzinn on Twitter.