TECHNIQUE | 10/05/2024 | 5.31pm
by Claudio Ghisalberti
«I have to get carried away with it a little but it’s a nice compromise». Filippo Ganna Rai microphones comment with these words on what is perhaps the greatest technological innovation of the Giro d’Italia. But what is the Italian time trial champion talking about?
Ganna talks about a variator which replaces the front derailleur and allows you to change the development of the relationship. The system is called “Classified” and allows you to have the advantages and functionality of a double chainring despite having mounted a single chainring. In practice it is about a reduction system. Practically the hub has two speeds: in Direct Drive the ratio is 1:1i.e. cassette and hub have the same speed (the pedaling development is that with the normal single chainring transmission). In Under Drive the ratio is 0.7: it means that for each revolution on the cassette the wheel makes 0.7 revolutions.
The advantages
The heart of the system is located inside the hub and would guarantee – precisely due to the lack of the derailleur – a reduction in air friction. Furthermore, the single chainring avoids disadvantageous crossings of the chain and possible falls of the chain itself. Working with a large chainring (today Ganna used one with 64 teeth, reduced by 46), according to the manufacturer, 45% of the friction in the chain itself would be avoided. The overall weight is approximately 580 grams. It means that the total weight of the bike is more or less the same as that of a bike mounted with a normal groupset.
How does it work
A button, powered by a small battery, located on the handlebar sends a wireless signal. The Smart Thru Axle, located in the thru axle, receives the signal and activates the gearbox located in the hub powered by a rechargeable battery. The hub receives the signal and shifts between 2 gears, similar to shifting a front derailleur between the large and small chainring. The total shift time is 150 milliseconds.
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