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Gearing for Monte Zoncolan

  • By Lennard Zinn
  • Published May. 23, 2010

Liquigas using 11-29

After the Giro d’Italia stage up and down Monte Grappa, I visited several teams at their hotels to check out the gearing and wheels that will be used on the bikes for Sunday’s stage finishing atop the brutally steep and long Monte Zoncolan.

The teams I visited will all be using compact cranks. We can all credit Fausto Pinarello for bringing the 110mm bolt circle diameter (BCD) to high-end road cranks; no need for triples anymore.

Most teams were switching cranks, since most of them had used standard 130mm BCD double cranks with 39-53 chainrings (other than the bikes equipped with oval chainrings from Osymetric, which cannot fit as small of an inner chainring on the same spider as a round ring could).

The Rotor ovalized rings, which a number of riders in the race are using, still will fit a 39-tooth on a 130BCD spider and a 34-tooth on a 110mm BCD spider.

Team mechanics were of course also switching cogsets, since the lowest gear most teams used on Monte Grappa was 39-26.

This will not suffice for Monte Zoncolan Sunday or for the time trial up to the Plan de Corones on Tuesday.

An interesting trend was how many teams will be using a 34-tooth inner chainring, yet how few will be using a 50-tooth chainring paired with it. 16 teeth is already a big jump for a front derailleur, and crank manufacturers generally offer just a 50-tooth, and perhaps also a 48-tooth, outer chainring to go with the 34, but no bigger.

The shift ramps on the outer chainring are also designed for such a pairing, and the recommended inner ring it’s designed for is usually imprinted on the outer chainring; it will say 34-50, 34-48, 36-50, 36-52, etc. on it.

However, most riders want a bigger top gear for fear of being dropped on descents, so, even though a high percentage of them will be using an 11-tooth small cog, they still want the big ring to be a 52.

With a little of creative work, mechanics can give it to them, despite both the 18-tooth jump between the 34 and the 52 generally being beyond the specs of the front derailleurs and the shift ramps on the outer chainring usually not being designed for such a combination.

To deal with the possibility of dropped chains when shifting down, many teams use inner stop devices to prevent the chain from falling off to the inside.

FILED UNDER: Bikes and Tech / Giro d'Italia / Road TAGS:

Lennard Zinn

Lennard Zinn

Our longtime technical writer joined VeloNews in 1987. He is also a framebuilder, a former U.S. National Team rider, and author of many bicycle books, including Zinn and the Art of Mountain Bike Maintenance and Zinn and the Art of Road Bike Maintenance, 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 degree in physics from Colorado College. Readers can send brief technical questions to Ask LZ.

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