I ride a Speed D7. The gears go from 34" - 92", and I think this is pretty good for most purposes. I bought my daughter an Eco 3, and while it also has seven speeds, it goes from 41" - 77". Everybody who rides this bike says that it is nice but it pedals too easy and it isn't fast. Does anyone know if it is possible to put a Speed D7 sprocket cassette on an Eco 3? The D7 has a Neo derailleur while the Eco 3 has a Shimano.