Good stuff. It's great to see some actual side-by-side experience cited as empirical evidence.As an example I have 2 bikes that are very similar. Both have 70cc (true) motors with the same hp modifications right down to the same style expansion pipe. Both have street tires and are well maintained. The biggest difference between them is that one has a Nuvinci hub and the other has a conventional derailleur. The Nuvinci bike has more top end and accelerates better.
July 25, 2008 at 12:09 pm
Switching from derailleur to shimano nexus -8 has reduced my average speed on a 14 mile commute by 6%. This indicates an efficiency reduction of over 15%, considerably more than you state above. We are getting definitive efficiency measurements done for greenpower electric car racing & I will try to post results here. Results from that forum suggest that the Nuvinci CVT is significantly less efficient still. Note that the shimano alfine now has roller bearings on its planet gears and their advertising proudly boasts “our most efficient hub yet”. With those bearings & OEM grease replaced by automatic transmission fluid, this hub might get up to rohloff standards for efficiency, which would be a profound improvement!
I think it's more of having the "right" gear with the NuVinci. 6th and 7th gear on a derailer bike are pretty much unusable with most of these motors - there's simply not enough power to keep going faster. Now if you have a nuvinci, you can get a slightly different ratio and eek out that little extra speed that there is still power for.Would it not stand to reason then that the higher top speed you mentioned with
the NuVinci is simply because of the higher overall gear ratio of the internal hub over
the traditional cog set?