The Giro d'Italia's Dolomites put the mechanics to work mounting smaller gears so their riders can survive the 2000 metre mountain passes.
We spoke to the riders and mechanics to understand what they use in the last mountainous week.
The Giro's final week crosses several famous climbs, including the Stelvio and the Mortirolo. The route through the Dolomite mountains to Ortisei on stage 18 covers three passes above 2000 metres and gradients often in the double digits.
"This Giro is a 38 or 39 [front inner chainring] by 30 [cassette], that's what we are using through this Giro without steep climbs like the Zoncolan or the Mortirolo from Mazzo," team BMC Racing coach and former rider Marco Pinotti told Cycling Weekly.
He pointed out to the sunny mountains around the start town. He said the roads are statale or bigger state roads instead of smaller local or provincial ones.
"We decided to use a maximum 30 in the back, and a 39/53 up front for everyone through the race, using a 30 in the back always on the climbing stages. This Giro doesn't have sections of 16 or 17 per cent.
"It has long and hard climbs, but they're statale roads.
"Some of our riders always will use 38, a little easier, but that's dependent on the rider, to give them more leverage when they attack."
BMC Racing uses Shimano, like most teams including Team Sky, Quick-Step Floors, Astana and Trek-Segafredo.
Portuguese mechanic Jose Eduardo Santos rushed around the Trek-Segafredo bikes. Others view him with awe as he is supposed to be one of the fastest wheel changers in the group.
"Bauke Mollema uses a 39-28 on most mountain days and a 30 on some other days," Santos explained.
"The other guys will use a 36-30, but Mollema always keeps a 39-tooth ring on, he doesn't use a 36. He'll keep the 39-28 on it as well for the Dolomite stage."
Watch: Bauke Mollema discusses his bike setup
Spanish rider Luis León Sánchez rolled by and stopped. His Astana team uses Argon 18 bikes with Shimano groupsets.
"I have a 39-32 today [stage 17], but I'll make changes every day," Sánchez explained. "I had that same for the Stelvio, a 39-32."
Belgian Iljo Keisse (Quick-Step Floors) trained on his rollers and laughed when he heard that BMC Racing uses 39-30 through the entire Giro.
"I change gears often, for the mountain stages, 38 in front, and 32 in the back. That's what I had on the Stelvio stage and I'll keep using it because I'm done, I had a really bad day [on the Stelvio]. On the steep parts I need the small gears because I have no more power!"
He said that the team mechanics do not need to switch cassettes, but wheels. They have the high-profile wheels with smaller cassettes and the low-profile ones with the climbing gears up to a 32-tooth gear.
Lotto-Soudal uses Campagnolo with different gearing options for their riders like Maxime Monfort and sprinter Moreno Hofland.
"We maybe have more options, but we don't have a 30 gear to use in a back, so it's 29 or 32 in the back, and the difference is a bit too big," Lotto-Soudal mechanic, Nick Mondelaers explained.
"Most of our men will use a 36x29 and some, the climbers with stronger legs, will have a 39 and a 32 in the back. Hofland, our remaining sprinter, uses a 36 by 29.
"On the normal stages or the other mountain stages, they use a 39 in the front and a 29 on the back. And that's more than fine for the normal stages."
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