The time trials: Where the Giro d'Italia could be won or lost

Three time trials, including a mountainous penultimate stage that echoes Pog and Rog’s yellow-jersey swap of 2020, could settle who wins this year’s maglia rosa. It’s why we hooked up with aerodynamic expert Xavier Disley, who’s worked with teams at the Giro, to dig deep into how he feels drag – or lack of it – will influence the remainder of this year’s race…

This year’s Giro d’Italia is notable for the amount of time trials with three sprinkled throughout the 21-day trawl from Costa Dei Trabocchi to Rome. The race of truth makes up 73.2km of the overall course. That’s still only 2.12% of the Giro d’Italia’s 3,448km but, like days gone by, will punch well above its weight when it comes to dictating who’ll wear the maglia rosa in Rome. (Miguel Indurain won five successive editions of the Tour de France, winning 10 stages along the way, all of which were time trials. Time trials matter, though less so in recent years when one, not three, has become the norm.)

Remco Evenepoel dominated the 19.6km prologue, beating Filippo Ganna by 22 seconds. Since then, the Belgian’s relinquished the pink jersey, crashed due to a sprightly canine and reeled back the years with an impressive display of keepie-uppies in Naples. But how will the Giro’s favourite fare come the next time trial on Sunday? Will he regain the pink jersey? Will he dominate once more? And what shape will he and his GC-challenging brethren be in come stage 20’s time trial that could decide this year’s race – the 18.6km mountainous parcours from Tarvisio to Monte Lussari? 

Here, we look to answer those questions and seek further aerodynamic answers with Dr Xavier Disley, founder of AeroCoach, a UK-based outfit who provide aero testing, fitting services and equipment for the world’s best riders…

Xavier, thanks for your time. Have you helped either riders or teams prepare for the time trials at this year’s Giro d’Italia? 

Yes, we have but – and I know this might seem weird – we don’t really talk about it. We work with several riders and teams, developing products and offering aerodynamic advice, and everyone’s fine with that. We treat everyone the same and, of course, keep our work private between them and us. But let’s just say if you watched stage one, you’d have seen much of our kit – wheels, drivetrain components, aerobar attachments, clothing… – at the top end.

Remco clearly looked on form in the first stage. Did you expect such a show of strength?

They had the wind coming from a favourable angle so they blitzed it, especially as it was so flat; that said, the speeds were surprising – Remco touched 58km/hr – but I guess that’s what talent delivers you. 

Remco Evenepoel won the opening stage at this year's Giro d'Italia (Image by

British readers and time triallists might be shocked by some of the speeds the top riders were averaging but they must bear in mind that WorldTour time trials tend to be straight out whereas British time trials are out and back. This means they’re significantly affected by wind speed and wind direction. For instance, if you have any changes in wind, it’ll affect you more on a straight-out time trial than a circuit. I actually think it’s bad to do straight-out time trials for that reason – it can favour some riders and hinder others.

Let me explain more regarding a rider’s shape as it highlights how, in time trialling terms, you approach the event from different perspectives. On one hand, you have potential winners of the stage, who are big, strong riders like Ganna (approx. 1.93m tall and 83kg), or you have smaller GC riders, like Evenepoel (1.71m and 61kg). There’s a massive difference in power output – a bigger rider like Ganna might generate 15% more watts than a smaller rider like Evenepoel – but the smaller rider is more aerodynamic. When you’re travelling at 58kph, a tiny change in aerodynamic drag – through positioning or gear choice – will save a lot in terms of absolute watts, whereas if he was riding slower, it’d favour the bigger rider and their absolute watts because the aerodynamic advantage would be smaller.

Read more: Remco Evenepoel's Specialized S-Works Shiv Disc time trial bike

We calculated that for Ganna to beat Evenepoel in the prologue would have required an extra 23 watts. That’s night and day; it’s not an extra gel, good sleep, bicarbonate or caffeine. It just highlights how much extra effort is required to close those kinds of gaps when you’re travelling that quickly.

One of Remco’s standout gear elements – like many over the past year – was his helmet. Aerodynamic thoughts, please. 

It would have made a difference as it’s effectively a personalised aero helmet whereas most of his competition use off-the-shelf helmets. That said, Ineos Grenadiers have a range of Kask helmets they can choose from. And you’ll notice other teams have slowly started to move away from one aero helmet for everyone. FDJ-Groupama’s sponsored by an outfit called Julbo but you’ll see their riders with Giro, Met and other helmets to suit the course. It’s similar at Trek-Segafredo.

At the top end, it’s really important as it’s one of the first things that hit the wind. It’s why many of the riders will be using rebadged AeroCoach [front] wheels. As it’s struck early, it can make a bigger difference to your drag compared to something outback like a disc wheel.

One final one on Remco, he forwent sleeves for a sleeveless suit. This seems to go against aerodynamic dogma?

Well, it depends on your position, the angle of your arms and how the rest of the skin suit interacts, plus the speed you’re riding at. They’d have done enough testing in the wind tunnel to see that it didn’t affect numbers too much, and it’s clearly more comfortable as Remco often goes sleeveless, probably due to cooling. He’d also shaved his arms; someone with really hairy arms racing at the top end would a big no, no! 

Looking ahead to Sunday’s time trial, it’s almost double the stage one distance at 35km. Would you expect a much different result than the prologue?

Whether a rider had a good or bad time trial on stage one, there’s little you can do between then and now. You can’t whip them out of the race of an evening and do some aero testing (although that’s a thought!). If you do make gear or positioning changes, you’ve got to be bloody sure that they’re the right ones, otherwise you could haemorrhage time, which you can’t afford when they’ll be racing at around 51 to 52kph and for around 40 minutes.

This year's Giro d'Italia opening with an uncomplicated TT along the coast (Image by

What’ll have bigger impact is what state they’re in. Riders have had crashes, while some will be more fatigued than others. And that’s what's so interesting about Grand Tour time trials. Stage one everyone goes into it fresh, like they would a World Championship time trial. By stage nine, it’s a different story, especially when you take into account their role in the team. 

Generally speaking, the leaders of each team tends to perform better because they’re more rested after being protected for days and days, whereas you might have a big strong rouleur rider who rode well in the first time trial who’s now knackered because they’ve either been protecting their leader or setting up sprints. As you move through a Grand Tour, that’s one of the key reasons why GC contenders tend to perform relatively better in time trials.

How will pacing strategies vary?

In all honesty, the best pacing strategy is to not die at the end, whether that means riding at a constant pace or speeding up at the end. What you don’t want is to be out of control of your effort. Do that and your power will drop and there’s nothing you can do about it. Again, it’ll come down to fatigue plus their experience of racing Grand Tours, though you find that the real top riders can maintain a high level of performance throughout.

Do you foresee any changes in equipment?

Not really. It’s mainly flat, a little technical but still not too long. You want the most aerodynamic set-up you have, meaning deep rims upfront and disc wheels. That also means lower tyre pressures than times gone by. Teams are really coming around to the idea that they shouldn’t be running 120psi on all of their wheels. They don’t need to run more than 85-90psi because the wheels and tubeless tyres aren’t designed for that. These days, they think of wheels and tyres as a system, rather than two separate components. 

Anton Palzer during his time trial along the coast to Ortana (Image by

Stage 20, an 18.6km time trial from Tarviso to Monte Lussari, features over 1,000m of altitude gain. How do you feel it’ll play out?

It’s in a similar vein to the Tour de France time trial of 2020 that saw [Tadej] Pogačar overhaul [Primož] Roglič, so could be very exciting. It’s flattish for over 10km but the last 7km or so is an 889m climb at 12.1%, so it’ll be interesting what happens in terms of swapping from a time trial bike to a lightweight bike. Maybe some riders won’t swap bikes – maybe the time trial experts who are used to climbing on those bikes – but I’d certainly expect the GC contenders and climbers to do so.

The bigger question might be: will the riders change helmets, too? If it’s a hot day and you have your face fully covered, like Evenepoel, or you have that balaclava thing wrapped around you, do you want to want to ride like that up a mountain? Absolutely not, it’s a terrible idea. But you can’t afford not to wear it for the flat bit because it’ll cost you loads of time. 

It'll be intriguing what they do. Will they leave their helmets on and just ditch the visors to provide more convective cooling? I know some helmets have vents, which you can open and close, so they may just open those come the climb. 

It’s all part of the aerodynamic problem that teams are trying to solve and it’s something many of the teams would have looked into in the wind tunnel. They’d have practised helmet and bike swapping in training, too, though there’ll always be some who’ll wing it and end up with botched bike changes. 

Filippo Ganna came second in the opening time trial (Image by

If temperatures rise as the race rolls on, could that have an impact on who performs in that final time trial?

Maybe if it was super-hot because beyond the lighter rider having an advantage uphill, they’ll have a heat advantage, too. If you have two riders going up a climb and they’re generating the same watts per kilogramme, the bigger rider will blow up first because they’ll be generating more heat. That’s because they might be doing 500 watts and the lighter rider 400 watts, so will become hotter and find it harder to dissipate heat. I don’t think that’ll be an issue in this race but I don’t think a rouleur will win the stage. 

Finally, will you have any further involvement with the teams and riders before the Giro d’Italia finishes in Rome on Sunday May 28?

Teams will ask for advice as the race goes on and we’ll help if we can. I had discussions with teams after stage one, where riders made mistakes, and they won’t do it again! Nothing huge but still enough to have an impact. We haven’t had requests for bespoke gear yet, though, which we’ve had in the past. That certainly challenges you.

Find out more about Xavier and the British outfit at

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