Author Topic: Greasing a hub query.  (Read 258 times)

tyreon

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Greasing a hub query.
« on: July 03, 2020, 12:42:44 PM »
Have a Shimano Nexus 8 speed hub. Maybe its 8 years old? Its been on several foreign trips and seems to be all working okay. Howsoever,most recently I've been wondering if/when its should need lubrication. My Dahon has mudguards and has never? been ridden in the rain,and kept in a garage. Its not in regular use as I use my other bikes. When,if or should it be greased/oiled? I wonder if,over time,its internal lubrication become sorta old(e),sticky,not-so-good? Or no,the lubrication is safely in there,the hub shows not signs of trouble,so leave it as it is. How do others see it?

As a PS,I very rarely lubricate my headsets and find them to be fine. Yes I'm not clocking up 5,000 miles a year,but then I see/hear/read others who seem to be dismantling/reassembling/greasing parts every year....which seems to be OTT in my world of cycling.

Your thoughts?
Ta

leftpoole

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Re: Greasing a hub query.
« Reply #1 on: July 03, 2020, 06:18:02 PM »
For what it is worth, I do not think these hubs require regreasing. I may be wrong of course.......

martinf

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Re: Greasing a hub query.
« Reply #2 on: July 03, 2020, 07:33:40 PM »
Shimano sell (or used to sell) a special, expensive oil for relubricating their 3,4,5,7 and 8 speed hubs. They advise dipping the innards of the hub in this oil, then allowing to drain. Which means you have to remove the internal from the hub shell. Not found out how often they recommend doing this.

My own lubricating procedure for Shimano Nexus 8 Premium hubs was to open the hub, remove the internal, then dunk it in synthetic gear oil. This is much cheaper than the special Shimano oil, but using it probably invalidates any warranty. I also grease the large outer bearing on the drive side and the smaller cup and cone bearing on the non-drive side with NLGI 2 marine grease, which I reckon acts as a barrier to water entry. I did this every year for regular use bikes, less often for the ones only doing low mileages.

I have recently changed this procedure. I now drill a hole in the hub shell. The position is critical, as the hole must not be over any of the steel bits inserted directly into the alloy shell. Then I tap the hole to fit a Rohloff drain plug. The idea is to simplify lubrication. Rather than dismantling the hub, about once a year I intend to squirt a small amount of synthetic gear oil in though the hole. I might also try the Rohloff rinse-drain-relubricate method.

I will probably still dismantle these hubs occasionally to regrease the outer bearings, but at longer intervals than previously.

tyreon

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Re: Greasing a hub query.
« Reply #3 on: July 04, 2020, 08:34:04 AM »
Thanks both for replies. I think I will be going with Leftpoole on this one.

martinf's reply maybe reasoned but my practical skills,tools and know-how in this job, could make any self lubing a costly trip to the bike shop for repairs. Sometimes the 5 minute job in the garage turns out to be hours,and my back isnt what it was. I dont think I could trust myself drilling anything  :-[

Ta both

martinf

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Re: Greasing a hub query.
« Reply #4 on: July 04, 2020, 09:50:17 AM »
These hubs are generally sold as not needing any routine maintenance. I reckon they are good for several years of low mileage good-weather use without additional lubrication, say about 5,000 kms. But the original grease will still slowly degrade with time.

In any case, Nexus 8 Premium hubs are cheap enough to be considered disposable (currently 70 for a new one on special offer at SJS cycles), so it may make sense to do no maintenance at all. And certainly not worth paying a bike shop to repair one if it does break.

My own experience is that dipping in oil improves the efficiency compared with the original grease, though this might also be due to some flushing away of the wear particles after the initial running-in period. The oil I use is Mobil SHC 75W90 synthetic, bought locally from a motor supplies shop, this hasn't caused any problems with the plastic parts inside the hub since I started using it in 2011. And as most of the family bikes are used in all weathers I also prefer to regrease the two bearings that are easily accessible. Drilling isn't absolutely necessary, it is a "perfectionist" tweak so that I can be more lazy about wheel removal.

Actually removing the internal isn't all that difficult, once you have the wheel off the bike you just need to undo the nuts and cone on the left side. I use a bench vise to hold the flats on the RH side of the axle, and  socket and cone spanners for the locknuts and cone. I then tap the left end of the axle to push the internal out from the right side. The whole thing comes out as a unit. Putting it back together is almost as simple as with an ordinary cup and cone hub, push the internal back into the hub shell, tap the right end of the axle to seat it properly, then adjust the LH cone till there is hardly any play, then lock with the locknut.

This is for the rim brake version, if you have a roller brake or coaster brake this may complicate the procedure a little.

I don't (so far) dismantle a Nexus 8 any further than this, haven't yet needed to, although as I have a total of 5 of them in service on family bikes I did buy the special tools needed for complete disassembly.

For me, the most awkward part of the job is not getting the internal out of the hub shell, but taking the wheel off the bike and removing and refitting the gear cable.


Andre Jute

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Re: Greasing a hub query.
« Reply #5 on: July 04, 2020, 06:49:37 PM »
In any case, Nexus 8 Premium hubs are cheap enough to be considered disposable (currently 70 for a new one on special offer at SJS cycles), so it may make sense to do no maintenance at all. And certainly not worth paying a bike shop to repair one if it does break.

That makes sense. Ten years ago, when I switched over to Rolloff, the Shimano service kit for the Nexus 7 and 8 speed boxes, comprising the oil in a container large enough to dip the entire gubbins of the Nexus hub into (once removed from the shell) plus a deep lid to stand the gubbins in to drip dry, cost Stg pounds 38 plus a hefty slug of postage because none of the kit was lightweight.

But there are millions of these gearboxes doing decades of service in The Netherlands and Denmark and other high-bicycle share countries without ever seeing a drop of oil. Especially now that we've discovered Tyreon isn't a time-served craftsman with a micrometer where other people have hands, I'd take my chances and if the box got wrecked, buy a new complete wheel off Ebay in Germany when the manufacturers sell off surplus complete wheels they didn't use; after Christmas they go as low as Euro 45 with a good rim and a quality machine build, sometimes with Sapim spokes. And I suspect this year will be a bonanza for cyclists who want to stock up on quality components.

BTW, though I've never heard of Shimano enforcing it, I seem to remember the recommended service interval for the Nexus 7 and 8 speed boxes, off a dealer information sheet I found in the German Shimano importer's very extensive archive, is the same as for a Rolloff, 5000km/3000m. On the same sheet I also found the Nexus Premium 8's mean time between failures, basically its expected lifespan, which was then (maybe a couple of years after the turn of the millennium) stated as 50000km/30000m.

martinf

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Re: Greasing a hub query.
« Reply #6 on: July 04, 2020, 07:36:19 PM »
Ten years ago, when I switched over to Rolloff, the Shimano service kit for the Nexus 7 and 8 speed boxes, comprising the oil in a container large enough to dip the entire gubbins of the Nexus hub into (once removed from the shell) plus a deep lid to stand the gubbins in to drip dry, cost Stg pounds 38 plus a hefty slug of postage because none of the kit was lightweight.

That was cheap. When I looked (probably in 2012) it was about 70 Euros plus postage. So just as cheap to get a new hub. Or damn the warranty and use synthetic gear oil, at about 10 Euros for a liter.

BTW, though I've never heard of Shimano enforcing it, I seem to remember the recommended service interval for the Nexus 7 and 8 speed boxes, off a dealer information sheet I found in the German Shimano importer's very extensive archive, is the same as for a Rolloff, 5000km/3000m.

Which concurs approximately with my home brew maintenance schedule.

On the same sheet I also found the Nexus Premium 8's mean time between failures, basically its expected lifespan, which was then (maybe a couple of years after the turn of the millennium) stated as 50000km/30000m.

That sounds good. Though I won't be disappointed if I only get a quarter of that distance.

Two of the hubs are on visitor bikes, so they probably get misused. For this use they are much less faff to maintain than derailleurs, especially the bike with the Chainglider, unfortunately I can't fit a Chainglider on the other visitor bike, which has vertical dropouts and therefore needs a tensioner.