Shimano Nexus 8 - disassembly, repair, maintenance or replacement

Disassemble Nexus 8 hub: Unscrew only three nuts, that's it!

Not all Shimano Nexus 8 hubs are compatible with each other. If you want to install a newer hub body or a premium version in an older hub and rear wheel, you should pay attention to one important detail: Is the Nexus pawl or Nexus centrifugal version installed?

The exchange of the hub body in my old Stevens Cityflyer year 2005 (Nexus SG-8R25 Premium) against a more modern Nexus hub body (SG-8R36 Premium) was not possible because the old versions of the Nexus Inter-8 are equipped with pawls. It does not matter if premium version or not. "Newer copies" of the Nexus 8 - at some point after 2005 - have a centrifugal clutch in the form of a roll cage made of plastic, with a similar appearance of a needle bearing.

Removed Nexus 8 hubs

The differences of the modern hub body Nexus SG-8R36 compared to an older Nexus SG-8R36 are hardly recognizable at first glance from the pinion side right. Worn or broken nexus hub bodies can be easily replaced, but only if they are compatible. As a result, no new rear wheel has to be purchased, just a matching spare part of the Nexus hub body of the Inter-8. Replacement hubs are sometimes new or used on Ebay or Ebay classifieds. Repairing or replacing the hub body is almost always cheaper than buying a brand new rear wheel with a Nexus 8 (premium) hub.

Incidentally, you can even get such a standard Nexus version Convert later into a Nexus 8 premium version with needle bearings, After all, the friction differences between the two hubs are around 4-6 percent, which are very noticeable in everyday use. Anyone who has ever driven the Nexus Premium version will certainly never want to worry about the standard version of the Nexus Inter-8 again ...

Nexus 8 hub body from 2005 and 2012

The old Nexus versions can be recognized by a Hub drum with obliquely machined grooves in the back area (on the right in the picture under SG-8R25). Here, the pawls can intervene. On the hub body itself, the pawls "in the form of a metal crown" are slightly off. When swapping the old hub body with the pawls and a newer hub body with the centrifugal drive (in a wrong hub drum), the Nexus breaks immediately on the first kick! Unfortunately, when installing the Nexus hub of this absolutely nothing to feel, because the parts fit exactly. Incidentally, I was able to save my old Nexus Premium hub with a cleansing and new lubrication of a rusty ball bearing. It was dipped in oil last year by my bike dealer, but over the wet winter, the water was probably back in the Nexus. The pedals now no longer rotate when pushing, the freewheel sounds präsiser, the wheel rolls again easily.

When replacing the Nexus 8 hub body, pay attention to the compatibility of the transfer bearing

Nexus SG-8R25 with pawls and Nexus SG-8R31 / 36 with centrifugal bearings in comparison

The older SG-8R25 with pawls can not be installed in a newer hub drum. The newer SG-8R31 or SG-8R36 has a smooth centrifugal bearing, which finds itself in the hub as a suitable counterpart. The same is probably true for the rare resignation version of the Nexus 8, which I have never had in my hands. There, the hub probably will not be the same inside.

Nexus 8 hub inside

The differences are also evident in the hub drum. The older SG-8R25 with pawls can not be installed in a newer, "round" hub drum. The newer SG-8R31 or SG-8R36 in the picture above transmits the power in the hub as a smooth centrifugal bearing (looks like a needle bearing). In the older Nexus drum are clearly visible metal grooves, in which the pawls can engage. It's like so often in life: If you know it before, it's obvious. Who does not pay attention, scrapes the hub.

Disassemble the Nexus 8 gear unit

Still, I'd like to encourage all screwdriver inside to quietly open the nexus hub when it makes a tick. In principle, it is quite simple, in addition to a 14er and 15er open-end wrench you only need a flat 14 cone wrench to hold the tapered tapered bearing nut (4., Bottom of picture). Contrary to all doubts, you do not even need a vise, but you can also hold the thread axis of the Nexus with a simple (10er?) Open-end wrench. However, the pinion with the fiddly snap ring must be removed from the hub body, two small screwdrivers help a lot, if necessary also with a. The more modern seals on the pinion side are made of metal and plastic, the older ones (8.) Only made of plastic. The newer seal version seals better and probably allows a slightly better freewheel with less resistance between pinion and freewheel body - that is, if you roll without kicking.

The Nexus 8 hub is not 100% sealed

Shimano Nexus 8 > Problem hub / Photo: Henrik P.

It goes without saying that a well-running Shimano Nexus 8 gear hub is not dismantled for fun. With fair-weather cyclists, a re-lubrication in the first year is not worth it at all. Such hubs are better left together. For cyclists, who often drive in the rain, regular maintenance is much more interesting: water and metal abrasion can not get out again. This creates a kind of "inner grinding paste" that likes to rust because of its tiny particles. In winter, aggressive de-icing agents can also penetrate and cause irreparable damage. A few drops of salt water are then enough to destroy the filigree mechanics over the years.

So there are often good reasons to disassemble the hub:

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