How to maintain a Shimano Nexus gear hub?

I have a bicycle with Shimano hub gears (Nexus 7 speed). I would like to know what type of maintenance it needs, besides the normal tuning.

There are four types of drivetrain maintenance you may want to do on a hub geared bicycle:

• Add chain lubricant when the chain squeaks
• Re-tension the chain as it wears and the chain slack increases.
• Replace the chain and possibly the front and rear sprockets when they are too worn
• Re-grease the internal gear hub

Of these, the three first trivial. The problem is the fourth.

I believe it needs some greasing, but I have no idea how to do it.

That's the problem. Few people have an idea how to do it. This is different from derailleur bicycles where the maintenance needed is very simple, although more frequent than on internal geared hub bicycles.

Some instructions are available on the Sheldon Brown web site:

• https://www.sheldonbrown.com/nexus-mech.html
• https://www.sheldonbrown.com/nexus7.shtml

Internal gear hubs are ideal for people who ride short trips, and are unable to perform maintenance on a bicycle and thus want a bicycle where the service interval is long. People who continue walking and push the bicycle when the rear tire gets a puncture (it's almost impossible to change the rear inner tube on an internal gear hub bicycle unless you consider getting your hands oily acceptable).

If I had an internal gear hub, I would just do chain and sprocket maintenance and ship the hub maintenance. If the hub wears out, it may be a sign that internal gearing might not be acceptable for the use case.

In addition to juhist's answer: Re-greasing the hub is possible, but messy. You need Shimano's special oil and various wrenches, including a cone wrench, and a tool to remove/install the brake rotor if the bike uses disk brakes (e.g. TL-LR10 for Centerlock), which in sum isn't exactly cheap. There are various YouTube videos that show the maintenance, e.g. here, here (german). There are also Shimano's service manuals (click on "Show all document types" and then enable "SM" again to view the list of hub gear service manuals) - 3 speed, 5 speed E-Bike, 7 speed, 8 speed, 11 speed.

However, given that the Nexus is the low-price variant, and the price of oil+tools, it's probably not worth it, unless you plan to re-lubricate many of those hubs. I did it with my Alfine 8 (SG-S7001-8), but can't recommend it to someone inexperienced (very fiddly and messy). If you do it wrong, you can end up with grease on the brake rotor if you use disk brakes, which will in turn destroy the brake pads. Also, each hub model is slightly different so you'll have to take a hard look at Shimano's exploded drawing of the hub and adapt the video instructions appropriately - e.g. the use of a hammer as shown in the 2nd video is wrong for some hubs, as they have an additional lockring that would be damaged this way, but the removal of which loosens the gear unit.