The TOUR Tech briefing for the 21st stage of the Tour de France 2025

Robert Kühnen

 · 26.07.2025

The TOUR Tech briefing for the 21st stage of the Tour de France 2025Photo: Getty Images/ANNE-CHRISTINE POUJOULAT/AFP
From 5 July to 27 July, the best cyclists in the world will compete in the Tour de France. Victory or defeat on the roads of France will be decided not only by the legs, but also by the equipment. The TOUR Tech-Briefing for the 21st stage.

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Tour de France 2025 - 21st stage: Mantes-la-Ville - Paris | 132.3 kilometres | 1100 vertical metres

The elevation profile of the 21st stagePhoto: A.S.O.The elevation profile of the 21st stage

The curtain rises on the final stage: the Tour traditionally ends on the Champs-Élysées, but this year with a three-lap loop over the Montmartre climb, which was also a central element of the Olympic race.

This changes everything. The classic sprint finish becomes a race in which puncheurs can pull away on one of the three crossings of Montmartre. After the 62 metres of elevation gain, the course drops slightly towards the finish. It is impossible for sprint trains to organise themselves here.

Already on the approach to Montmartre, the field will stretch out and tear itself apart on the climb.

The ascent to MontmartePhoto: A.S.OThe ascent to Montmarte

In our simulation, we assume an attack on the last crossing of Montmartre. After such an attack, which bilke is mathematically the best basis for an escape?

The number of the day: One second

The fastest bike for the attack on the Montmatre and the extension of the escape to the finish is the most aerodynamic bike in the field: the Van Rysel RCR-F Pro narrowly wins out over the Cervélo S5.

The (almost) complete field at a glance*

tour/stage21-25_0ab2b8249477ba80e427d790fdea2027Photo: Robert Kühnen

*) The calculations are based on the bikes tested by TOUR in the laboratory and wind tunnel. The bikes at the Tour de France may differ in some details. Of course, we have also not yet been able to analyse last-minute prototypes. Background to the simulation.

Our expert

                               Photo: Robert Kühnen

Robert Kühnen studied mechanical engineering, writes about technical and training topics for TOUR and develops test methods. Robert has been refining the simulation calculations for years and they are also used by professional teams.



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Robert wurde 1964 in Düsseldorf geboren und fuhr seine ersten Straßenrennen mit 17 Jahren. Zum Spitzenrennfahrer reichte es nicht, aber zu späten Nischenerfolgen. 2011 gelang es Robert, Zeitfahrweltmeister der Journalisten zu werden. Nach seinem Maschinenbaustudium in Essen führte ihn sein Weg bereits 1993 zur TOUR, wo er anfangs mit der Legende Hans Christian Smolik zusammenarbeitete. Heute ist Robert freiberuflich für TOUR und BIKE unterwegs, mit den Schwerpunktthemen Aerodynamik, Messtechnik und Entwicklung neuer Prüfmethoden. Motto: Geht nicht? Gibt‘s nicht. Robert berät auch die Radindustrie und Profiteams, coacht Athleten und kümmert sich um den Radsportnachwuchs. Als Radsportler mag es Robert kurz und schnell, auf schmalen wie auf breiten Reifen.

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