Once upon a time bikes came as single speeds – one gear. Enviolo (formerly Nuvinci) takes gearing to the opposite extreme – continuously variable gears!
Gearing refers to the ratio between the travel of the cranks and the rotation of the drive wheel. High gearing means lots on wheel movement for a little crank movement – great for the flat or downhill. Low gearing means lots of crank movement for a little bit of wheel movement – great for steep hills.
On a high wheeler (a penny farthing) the rotation ratio was one to one. Every time the cranks go round the drive wheel goes round. Because the drive wheel is very big and the cranks are relatively small, the small movement on the crank means a big movement on the ground (a high gear) so you can go fast but will struggle up hills.
Modern single speed bikes have have a single chainring (attached to the cranks) and a single sprocket (cog attached to the rear wheel). The ratio can only be altered by changing either chaining or rear sprocket which is not the sort of thing you want to do each time you arrive at the bottom or top of a hill.
Most modern gear systems offer changes of ratio either by:
- moving the chain between multiple chainrings or sprockets (derailleur gears)
- or doing clever things inside the rear hub which again changes the amount of chain movement needed to rotate the wheel.
With derailleurs you can have up to 30 gear option and 14 for hub gears – though most bikes have less than this. The more options you have, the more you can keep in a ratio you find comfortable – not to fast or slow, not too easy or hard.
Enviolo – now for something completely different
With Enviolo you have an infinite number of gear options. Imagine not just 3rd gear but 3.1 or 3.875 – you select exactly what you want using a twist grip a bit like the volume knob on a radio with no jumps between levels as you get louder of softer.
This trick is achieved by doing clever things with balls as shown below:
All this fits into the rear hub. To find out move about the technical aspects check out the manufacturer’s website.
The assembled hub looks very similar to a standard hub gear set up.
Can I have one?
A number of high end e-bikes come with the enviolo system including Koga and Tern – we sell both.
Koga have also installed an automatic version of the system on their E-Nova Automatic :
With the Enviolo Automatic hub gear system your own custom cadence is maintained, regardless of your speed and conditions. Makes gear changing entirely unnecessary.
The Tern GSD is fitted with the manual version.