Originally Posted by
alhedges
Many people are happy with 7 and 8 speed IGHs. However, one of my friends experienced premature failure on both a Shimano nexus 7 and later 8 speed hub. (On a trek navigator). The failure may have been related to the fact that he road in dusty conditions, or that his bike was pretty heavily loaded, or to some other unusual reason...
It is the load, not the dust. The Nexus 7sp and 8sp hubs aren't really designed to handle high loads. The SRAM S7 seems to handle them better, although friends have still damaged them with very high torques (using them in combination with a Stokemonkey electric motor). The Rohloff is the only internal hub that I'm aware of which is designed for tandem and cargo loads besides the SRAM 5sp Cargo hub. I do know a number of people who run SRAM S7 hubs on cargo bikes without problems.
I'm curious to see how the new SRAM i9 holds up in use. The design isn't as simple as the S7. It looks like I've sold my Tikit with the S7, so I'll be putting an i9 on the Tikit that I'm keeping.
alex