I wrote this a while ago and posted it on the old forum but forget about it until now. It’s something I thought of and might be of interest.
Anyone who frequently switches between a derailleur and a NuVinci equipped bike may have noticed that there a something different about a NuVinci bike, apart from having no gears. The way the pedals respond when you push against them, there isn’t that feeling of a direct connection you get with derailleur gears.
Having read the topic “Inner gear ratios of the NuVinci 360” it made me think, could this be explained by something that was written about in this topic?
What is the effect when the bicycle is being ridden of having the ratio to some extent dependant on how much torque is transferred through the hub?
It is written in all the N360 specifications that the ratio range is 0.5 underdrive to 1.8 overdrive. However it has been discovered that with an extremely low torque the range is higher at 0.56 - 0.58 underdrive to 2.0 – 2.1 overdrive.
This means that in the “dead spot” of your pedal stroke the ratio will be higher, which is the same effect the Biopace type of elliptical chainwheel was designed to create.
The original elliptical chainwheels are the opposite and have a lower ratio to get you through the “dead spot” quicker.
There have been a lot of debates in the past about the benefits of non-round chainwheels and which type is best. As far as I can tell due to the way the NuVinci hubs work you end up with the equivalent of an elliptical chainwheel whether you like them or not.
According to my calculations the change in ratio between the power part of the pedal stroke and “dead spot” is approximately equivalent of a 42t chainring becoming a 48t.It depends on a lot of factors but it gives a rough idea that what I’m talking about is not insignificant.
As the ratio change is driven by torque could this be like a perfect biopace chainring?
An advantage of biopace chainrings is better traction. I’m convinced that NuVinci hubs have the same characteristic. I have slick tyres on my bike and I’m always amazed at how much traction I have when off-road. The lower the ratio and the harder you crank the pedals the more elliptical the chainwheel that the hub mimics and the more it smooth’s out the power to the wheel.
Anyone who frequently switches between a derailleur and a NuVinci equipped bike may have noticed that there a something different about a NuVinci bike, apart from having no gears. The way the pedals respond when you push against them, there isn’t that feeling of a direct connection you get with derailleur gears.
Having read the topic “Inner gear ratios of the NuVinci 360” it made me think, could this be explained by something that was written about in this topic?
What is the effect when the bicycle is being ridden of having the ratio to some extent dependant on how much torque is transferred through the hub?
It is written in all the N360 specifications that the ratio range is 0.5 underdrive to 1.8 overdrive. However it has been discovered that with an extremely low torque the range is higher at 0.56 - 0.58 underdrive to 2.0 – 2.1 overdrive.
This means that in the “dead spot” of your pedal stroke the ratio will be higher, which is the same effect the Biopace type of elliptical chainwheel was designed to create.
The original elliptical chainwheels are the opposite and have a lower ratio to get you through the “dead spot” quicker.
There have been a lot of debates in the past about the benefits of non-round chainwheels and which type is best. As far as I can tell due to the way the NuVinci hubs work you end up with the equivalent of an elliptical chainwheel whether you like them or not.
According to my calculations the change in ratio between the power part of the pedal stroke and “dead spot” is approximately equivalent of a 42t chainring becoming a 48t.It depends on a lot of factors but it gives a rough idea that what I’m talking about is not insignificant.
As the ratio change is driven by torque could this be like a perfect biopace chainring?
An advantage of biopace chainrings is better traction. I’m convinced that NuVinci hubs have the same characteristic. I have slick tyres on my bike and I’m always amazed at how much traction I have when off-road. The lower the ratio and the harder you crank the pedals the more elliptical the chainwheel that the hub mimics and the more it smooth’s out the power to the wheel.
- Oran