How to put an oil port into an internally geared hub
December 23, 2010
I had an SRAM i-Motion 9 internally geared hub. It died. I replaced it with a Shimano Alfine 8 internally geared hub. Both of these hubs are really well sealed, and come pre-packed with grease (come to think of it, the SRAM was pretty lightly lubed in there). Other hubs, for example everything from a Sturmey-Archer 3-speed, to a Rohloff 14-speed, come with an oil port, so you can add and replace the lubricant pretty easily, and the oil has a bit lower friction than grease. So, some people put oil ports in their sealed hubs. I decided that I wanted one, too.
However, I was a little nervous about tearing apart my hub, and just putting a hole in it. Things could go wrong. So I practiced on the old SRAM shell (3 times), and for the rest of the world’s edification, I made a movie of one of the practice holes. One take, 17 minutes long. 13/64″ drill, 1/4-20 tap, nylon license plate nut.
I’ve since done my real hub, and it now has about 2 tablespoons (30ml) of Mobil 1 synthetic ATF in it. The process was pretty much like this video, except that I was much more careful about the metal bits (which are, however, aluminum, and should get eaten like chewing gum by the hardened steel gears). In the Shimano hub, there are some hardened steel races set into the hub shell itself; don’t try to drill through those. Notice also that I was pretty gentle with the steel punch; you want the tiniest little pit in the surface.
If you try this yourelf and screw up your own hub, don’t come crying to me. Nonetheless, here’s photos showing how to dismantle your hub — you only need to remove the complicated guts, in order to mutilate the hub shell. I think the grease seal may be reverse-threaded; just be aware of this possibility.
Update: I don’t know that I recommend this after all; I could never get the hub to stop leaking oil, even when I only put about a tablespoon (15mL) in. Couldn’t bring it in doors, had to keep cleaning off the brake rotor, just didn’t do what I wanted. I shot some grease in instead.