What is the benefit of an oil bath or a maintenance in a Shimano Nexus / Alfine 8-gearshift?
In the winter 2017 when pushing my everyday bike Stevens City Flyer suddenly turned on the pedals. For me it was an alarm signal: The internal friction of the Nexus 8 Gang premium hub was suddenly higher than usual after 12.000 kilometers and twelve years of everyday use. At first, I attributed this to the fall of winter temperatures near freezing: probably only the fat was frozen stiff. But I could not remember that ever before. The pedals turned in all gears when pushing, even when cycling even in the freewheel they had since autumn the urge to rotate without feet while rolling by itself.
My guilty conscience reported: 12 years and 12.000 kilometers not serviced on the everyday bike! Shimano's maintenance recommendation for the Nexus 8 circuit is every two years, or remove all 5.000 kilometers, clean them, put them in an oil bath, and then reinstall them in greased condition. Although the major advantage of a hub gear through your encapsulation from dirt is mainly to be virtually maintenance-free, even tiny, abraded metal particles remain in the hub. You can not simply fall off like a derailleur, but permanently sand on the surfaces of the ball needle roller bearings including the bearing surfaces. The hub wears out, so to speak, through your self-generated metal abrasion, which is trapped in old grease and oil in the form of a deep black, metal-coated abrasive paste.
Gear hub oil change on the bike
With the hope to save the hub gear a few more years, Some bike retailers are offering a costly oil change that bothers the bicyclist budget of fabulous 50, - EUR similar to the oil change of a full-sized small car. For this purpose, the inner switching unit of the Nexus (or Alfine 8) hub will turn into a special, wickedly expensive one for a few minutes Hub oil from Shimano dipped. After draining, the ball bearings are still with a white Shimano special fat massaged, the switching unit is reinstalled in the cleaned hub and the rear wheel is mounted again. A matter of a good hour with waiting times. I have now made it unique with my bicycle dealer and was thrilled. The hub runs since then freewheel easier again, the pedals do not turn when pushing, the gears engage a little more precisely.
These positive effects reinforced after a hundred kilometers of cycling yet, A fountain of youth for my Nexus Premium as well as for my legs! The measure is therefore convincing for frequent travelers or bicycle commuters. For my taste but quite expensive, especially with us in total There are three Shimano Nexus gear hubs in the garage. I understand quite well the working time of the bicycle mechanic, special tools, special Shimano oil for gear hubs to the incredible moon price of 65, - Euro per liter (!) With matching oil bath plastic can for diving. In addition, you need the white Shimano bearing grease for the ball bearings. Outrageous? Yes but You can also make the oil bath much cheaper yourself.
Incidentally, the Shimano Alfine 11 gears and the expensive Rohloff hubs have a small maintenance hole with a sealed grub screw in the hub, with which you can make an oil change even without disassembling the hub. There are also individually modified nexus hubs of bicycle freaks, which have been subsequently provided with an artificial maintenance opening for oil change. The matter is more complicated because the hub has to be sealed extra for oil filling. Otherwise, the oil pulls into the tires via gravity or drips onto the rims (brakes!).
I'm a real fan of value, but that's money-making. It also has to be cheaper for frequent travelers. I went to international bicycle forums, bicycle world traveler sites, and bike screwdriver gurus. During the research came out for me: You can do the maintenance for an acceptable price with some Schraubertalent yourself, because the Shimano Nexus hub is also quite maintenance friendly for Otto-standard screwdriver constructed in several modules. The disassembly of the gear unit consists of a single unit that does not need to be further disassembled.
The only special tool required is a vice and a narrow 14er (or 15er) cone key.
Shimano Nexus 8 gear unit disassembly
- Basically you just have to extend the rear wheel with the Nexus 8 or Alfine,
- Unhook the Bowden cable and release the Bowden cable holder with half a turn of the clamping mechanism
- Unscrew the snap ring in front of the pinion (very fiddly with two screwdrivers or / and pliers)
- the hub from the left side (not the pinion side) start to disassemble
- To do this, clamp the axle of the rear wheel on the smooth side in a vise (pinion side is down)
- Unscrew the 15 nut, remove the black plastic cap and the metal collar
- Use a narrow 14er cone wrench and a standard 14er open-end wrench to unscrew the countered nuts
- et voila, then the complete Nexus gear unit can be pulled out of the hub
- If you do not get any metal fragments or brown powder, it's all in butter
Clean gearbox, oil and grease bearings
- Clean hub from inside of old grease and dirt.
- Clean gear unit externally with a clean cloth, only use parts cleaner on rusty or extremely dirty hubs, as this dilutes the oil
- For defective bearings or strong running marks (pitting), the ball bearings or bearing shells / cones must be renewed.
- The hub does not need to be disassembled otherwise, the innards - in particular the pawls should never be lubricated with grease - but only oiled.
- As oil bath is simply a commercial gear oil for scooters or motorcycles taken (liter price about 10, - Euro).
- As an oil container for diving, for example, an empty, 0,5 liter yogurt cup can be used, or a cut-open water bottle.
- The Nexus or Alfine gear unit is inserted into it at most up to the taper bearing of the drive side at least 1h, possibly turn the planetary gears in between and dive again.
- The hub must be drained thoroughly to prevent excess oil from running along the spokes into the rims or hoses and tires.
- The two conical ball bearings on the outside and the large ball bearing on the pinion side are additionally coated with high-quality, water-resistant bearing grease. The forums say: Use white grease with a high proportion of nylon or silicone. It must not swell the plastic parts and seals used. Camp game without violence with feeling set.
- Caution when mounted rollerbrake brakes: These can get very hot and the bearing grease melts. Be sure to ask a retailer for the correct, heat resistant grease or use the recommended Shimano special grease. This also applies to Nexus coaster brakes.
- Hub and rear wheel are re-installed, the rear wheel is not easy, the bearing clearance is set too tight and must be corrected. If the rear wheel has a slight play or wobbles easily, the bearing has to be tightened again.
- The pedals should now no longer rotate when pushing, the correct smooth running effect began with me but only after about 100 kilometers cycling.
The bicycle forums use the following lubricants for hub maintenance:
- Oil for automatic transmission
- Transmission oil for motorcycles or cars (my tip)
- High fat nylon (Original Shimano No. Y-041 20800)
- Good rolling or ball bearing grease
The Gretchen question is: What oil and grease can be used to service the Shimano Nexus / Alfine hubs in freewheel, rollerbrakes or resignation versions?
Answer: I'm not sure, but with this article I'm going to encourage you to try it for yourself instead of waiting for the hub to break completely without maintenance. With a bath in gear oil SAE 80W90 you certainly do not do anything wrong first (no guarantee). If you have had good experience with certain lubricants, may please write me, I will publish the information here. Incidentally, the almost maintenance-free rollerbrake brake itself requires Shimano Rollerbrake special grease once a year to function reliably. Visitor Henrik P. has eg over his Scraped Nexus 8 hub annoyed at the e-bike and now dives regularly even in oil. My motto: oil from the aftermarket is much better than none!
New Nexus hub instead of repair and maintenance
Understandably enough, many bike retailers are replacing the entire interior of the Shimano hub with a new gear unit rather than trying to make it workable again - let alone fixing it. The time required and the high risk of a defective hub is understandable. But if you spend some time with your own screwdriver ambition and do not shy away from dirty hands, you can save your hub gearbox with very little tools and manageable effort over many years. I will now increase my hub circuit maintenance cycle from the former 12 years to every two years. I know now how it works and what it brings ...
My subjective conclusion with a Nexus Premium hub from 2005: The Shimano Nexus and Alfine hubs are only "maintenance-free" if their base lubrication is renewed by expert hands every x-thousand kilometers. Whether this really must be all 2 - 3.000 kilometers according to Shimano maintenance plan or whether - like me - more than 12.000 kilometers passes easily, the truth is probably somewhere in between. It can go well with Shimano Hubs even without maintenance long.
A derailleur must be constantly maintained and still with good care: All 2.000-3.000 kilometers do it well, replace the wearing parts. Problems have become known in Nexus winter drivers inside: The right ball bearing velvet cone on the pinion suffers from massive wear by penetrated dirt. A rough run when freewheeling backwards the pedals with the hand in the state announces this evil.
In older versions of the Shimano Nexus hub also likes to say goodbye to the big nexus ball bearing in the vicinity of the drive pinion in the form of zerborstenen bearing items that scrap the entire hub in the shortest possible time when driving through metal particles. Both ball bearings on the pinion side should therefore be kept in mind. Shimano has changed the seals more often over the Nexus 8 series to improve freedom from maintenance. Therefore, many hubs from different years of construction differ in particular by their seal variants. Care when ordering spare parts and when installing the Nexus gear unit in foreign Nexus hubs from other years ...
Links and sources for the maintenance of gear hubs