The Giro d'Italia's Monte Zoncolan climb will require the riders to be ready, but also their bikes with gears that will allow them to handle the high and consistent pitches up to 22 per cent.
Chris Froome (Sky) will ride with a 34-tooth front ring and a 32-tooth in the back. Race leader Simon Yates (Mitchelton-Scott) is still deciding.
"We've been up the climb in recon," Sky mechanic Gary Blem said. "It depends in the race. He uses 38 and 30 in a stage with peaks of 15 per cent, but on the day to Zoncolan, he prefers a 32 on the rear and a 34 on the front just to spin the legs a little more.
"We try to give the riders the gearing they require, the stages are long and so it's good to have that extra gear so they don't kill their legs. After the 200-kilometre stages, summit finishes, the guys are tired and we try to give them a little extra."
The road climbs for 10.1 kilometres and averages 11.9 per cent. Many insiders call it the hardest climb in cycling, worse than Angliru or Mortirolo.
"It's constant and steep, maybe the one of the most difficult climbs in Europe or the world maybe," 2011 Zoncolan winner Igor Antón (Dimension Data) explained.
"You need a 34-32, it's better for the cadence. If you need to shift down, you can do it, but if you don't have that easier gear to shift too, it's a problem."
"I don't know what I'll use yet, I still need to decide," Fabio Aru (UAE Team Emirates) said. "It'll be a compact with a 34 or 36, but we'll talk tonight. Behind? I'll decide tonight what to use."
"I'll use a 36 and a 30 in the back," Davide Formolo (Bora-Hansgrohe) said. "I think that will work for me. I've never done the climb, not evening in training. But a climb is a climb, right?!"
Other stars prefer to keep their gear choices to themselves.
"We've decided on the gears, but I'm not going to tell you," Tom Dumoulin (Sunweb) explained. "Yes, it's a secret for my rivals."
"We know the gears, but we are going to keep it secret," Julien Pinot, team helper and the bother of Thibaut Pinot (Groupama-FDJ) said.
"It's one of the hardest climbs in Europe. The climbers aren't used to climbing the hard gradients. Even compared to Angliru it's harder.
"We are going with very easy gears. We prefer the rivals don't know. But we all have Shimano gears, so it's 34 or 36 and then 30 or 32 in the back."
The riders will essentially use the smallest gears possible on their bikes. EF Education says that they tested a Dura-Ace derailleur with a 32 gear and it works fine, other teams say that to use that 32-gear Ultegra cassette that you need to use an Ultegra derailleur – which is heavier.
"We'll use a compact on the front with a 52-34 with and a 11-32 in the back," Geoff Brown, EF Education mechanic said. "Michael Woods and the entire team will use it. The directors like to have all the riders on the same gearing in case a wheel change or bike change is needed for Mike."
"They will be all a 36 or 34 up front, with a 30 in the back. Some on a 32," Mitchelton-Scott mechanic, Tullio Pellicioli explained. "Chaves will use a 34-30. Simon Yates? The same as Chaves or a 36-32."
"I'll be on the smallest possible, so I think it's a 34-32, because it's bloody steep," George Bennett (LottoNL-Jumbo) said. "It's long and steep. I will try to have a small of gear as possible. Also the climbs before are steep as well, so it'll be about saving energy possible."
Lotto-Soudal with Tim Wellens and UAE Team Emirates with Fabio Aru are some of the few with Campagnolo groupsets.
"They can choose what they want: a 32 in the back or 29 and then a 39, 36 or 34 in the front," Lotto-Soudal mechanic Frederik Moons said.
"They make the call and we put it on. They message us in a WhatsApp group. We remind them so we make sure everything is right in the morning.
"Wellens? He's quite difficult to choose. I think a 32 if he doesn't change in the front from a 39, if he does change to a 34 or 36, then maybe a 29. But it's still mystery!"
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Gregor Brown is an experienced cycling journalist, based in Florence, Italy. He has covered races all over the world for over a decade - following the Giro, Tour de France, and every major race since 2006. His love of cycling began with freestyle and BMX, before the 1998 Tour de France led him to a deep appreciation of the road racing season.
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