Repair Nexus 8 gear shift

The premium version of the Nexus 8 gearshift fits into the hub body of the Nexus standard hub and can be easily replaced or repaired. Photo: © VELOTOP


The conversion of a Shimano Nexus 8-Gang Standard hub to the smoother premium version is relatively easy, without the hub body auszuschichen from the rear wheel and back.
Bicycle dealers recommend for hub gear repairs for "economic reasons" immediately like a completely new rear wheel with a new, already spoked Shimano Nexus hub. Unfortunately, the dealers are right in many cases, because a targeted repair of the circuit innards after tens of thousands of kilometers is only something for real experts. Since no one dares to really ran and there is too much time for the repair on it, which does not pay for a customer afterwards, because there are simply too many sources of error. The qualitative standard deviation in Shimano hub gears is very high, especially in the simple hub gears with resignation.

But what works is to completely replace the gear unit of the Nexus 8 gearshift, if the hub is not severely worn. This will save you a new rear wheel, or can replace the Shimano Standard Nexus 8 gearshift through the premium version. Depending on the selected gearbox, this results in a higher efficiency of 3-6%, because the individual gear wheels of the planetary gearbox of the Nexus Premium version run with smooth-running needle bearings, while the unfortunately still sold standard version runs with much heavier plain bearings. In everyday cycling this is a noticeable difference, especially for speed and touring riders. An overview of the differences between the Shimano hub gears > is available in this article.

Replacement of the defective Nexus Standard 8 gear shift with the Shimano Nexus premium version

Repair Shimano Nexus hub gear

My Dahon Bullhead with defective Nexus standard 8-gear hub gear. Too bad to stand around, since it was after the replacement of the nexus circuit really fast.

I think the Nexus Premium 8 gear hub is better than their reputation. She likes cracking in the 4. Gang, but still does your job smoothly for over 13 years (or 15.000 km) in my Stevens Cityflyer. On my Dahon Bullhead folding bike, however, the Nexus Inter-8 standard circuit had a quirk since delivery 2011. Grinding and grinding noises, a power-consuming fourth gear and a pedal that always wanted to spin powerfully in the freewheel instead of running free were a disappointment with Shimano's 8-Gang Nexus gears. The rear wheel was reclaimed by me and came again greased and adjusted here again, in winter it was due to the tough fat at low temperatures but more difficult. The warranty expired after that. The circuit actually worked, but not very well - the folding bike just did not work well.

A workshop then swapped 2014 for my oil, better, but unfortunately not as good as the smooth-running Nexus Premium version from my other bike. A detailed article on the maintenance and lubrication of the Nexus 8 can be found here. In addition, the grinding noises were still there. The Dahon Bullhead was barely driven by me, although it is a great folding bike for the money except for the circuit! The superstable diamond frame with comfortable ergonomics is unique among folding bikes. See Dahon Bullhead and Dash review.

400, - EUR for a new 20 inch rear wheel with Nexus Premium 8 gearshift and wide rim as custom-made?

For me, there were only two solutions left. A new Nexus Premium or Shimano Alfine hub, or just a brand new rear wheel - of course for economic reasons ... The 20 "rear wheel should incl including Nexus Premium circuit with a wide, stable rim as a special order on 400, - cost EUR. That was out of the question for economic reasons. 20 "inch rear wheels with premium or Alfine gear are not available off-the-shelf. They are always expensive custom-made products. I wrote several emails to rear wheel manufacturers, nobody wanted to help. I had already resigned myself to spice up such an 20 "rear wheel with Nexus Premium hub on long winter evenings. The last time I spank my bike is about 35 years ago ...

In another extensive Internet research, I came across an older, English-language website, which described that a replacement of the Nexus standard gear unit should be possible against the premium version in the same hub. The website is unfortunately half destroyed, but here is the link to hubstripping.wordpress.combecause there are really some very interesting things to discover for Shimano hub gear experts. According to this website, for example, you can completely exchange the Nexus SG-8R20 offal for the SG-8R25 in one and the same Shimano Nexus hub body. That was exactly the solution to my problem.

Conversion of the Nexus gear unit into the old hub

Common reason for bad nexus circuits: non-parallel dropouts on the frame. This is where the geometry is right.

First, the dropout symmetry on the frame was measured by my bicycle dealer VELOTOP, and they still fit together neatly - according to Shimano, oblique frames are a common cause of poorly running hub gears. Photo: © VELOTOP

VELOTOPIn my neighborhood, 2015 just opened a new bike shop at the time: VELOTOP. I talked to managing director Andreas Beusker about my problem - understanding, he admitted that you could possibly change the gear unit of the Nexus hubs from standard to premium, but it's just an experiment. After consultation with his technicians Felix and Shimano he made me a fair offer on my responsibility, if the conversion of the circuit unit should not work. There were a few more inconsistencies when replacing the gear unit of my four-year-old Nexus Inter-8 (SG-8R31) with the better premium SG-8R36 hub, which was to be built into the old SG-8R31 hub body. The almost new premium version of the Nexus hub, I have purchased on the Internet from a dealer, since it was already installed in a wheel and could not be sold as brand new.

The new Nexus gear unit is inserted into the old hub

The new Shimano Nexus Premium gear unit is used in the old standard hub, which now runs easily with needle bearings. Photo: © VELOTOP

Short and painless: The conversion of the Nexus gear units in the same hub body worked great. The result is exactly as I had imagined: The folding bike is lighter and noiseless. The pedaling requires noticeably less force with the new Nexus Premium, during a test drive with the folding bike I have now reached 20 km / h despite the 55 inch wheels downhill relatively effortlessly. The Schaltbowdenzug had to be adjusted a bit. The yellow dots are now aligned exactly on top of each other. And last but not least: Even at this wedding of older Nexus hub and the newer premium gear unit crack the fourth gear happy again happy. Obviously this has to be the case with Shimano 8 gear hub gears. Even the Shimano Alfine is not really free from it today. But hey, I can live with that very well. The bike has now become really fast with inflated tires - after all, only after 4 years of ownership!

Attention: Of course, I can not guarantee that this change works in all possible combinations of the Nexus 8-Gang family. There are, for example, resignation versions in which the hub is designed differently due to the design!

Supplement in summer 2018: The replacement of the hub body in my old Stevens Cityflyer year 2005 (Nexus SG-8R25) against a more modern Nexus hub body (SG-8R36) of 2012 was not possible, although the hub body fit perfectly into the hub barrel. She was immediately destroyed on the first kick .... > Details for opening and compatibilities

Adjust the bearings after replacing the nexus offal

Adjust the bearing clearance of the Shimano 8 gear hub after replacing the Nexus gear unit. Photo: © VELOTOP

I would like to thank Andreas and Felix for the repair of the hub and the photos, which they kindly did during the conversion to Nexus Premium in the workshop at VELOTOP in Bielefeld. Certainly, this conversion manual is also good for all cyclists inside who just want to have their hub repaired, instead of buying a new rear wheel. Looking back, I would compare to the premium version never again buy a Shimano standard nexus circuit, The Nexus Standard Inter-8 just runs much worse and harms the image of Shimano as a manufacturer of good hub gears!

Swap Nexus Standard for Premium

Finally, the old Nexus standard gearbox was built into the new Nexus Premium hub body. That too worked fine. Photo: © VELOTOP

Links to the repair and conversion of Shimano Nexus circuits:


www.velotop.de from Bielefeld carried out the conversion and took the photos

hubstripping.wordpress.com Unfortunately, only fragments of concentrated Shimano Nexus insider knowledge

Overview of all current Shimano Nexus 8 hubs on paul-lange.de

Overview of all workshop books from the Shimano Nexus hub on paul-lange.de

Download service instructions to the Shimano Nexus 8 speed shift hub SG-8C20 by Paul Lange


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