mc510

My "new" (about 250 miles at this point) Shimano Nexus Inter-8 hub drags a lot when freewheeling, and with my hand on the pedal a distinct grinding sensation is transmitted (kind of similar to feeling from a freewheel hub with cones adjusted way too tight). If I give the rear wheel a moderate spin, it comes to a stop very quickly (can you tell from this video clip?) Just had the bike in for free after-sale checkup (at Performance Bicycle) and their head mechanic said that it's normal ... but he also tried to upsell me on a bunch of unnecessary stuff, so he doesn't have a lot of credibility with me. But I'll believe the bikeforumers, so what say those of you with this hub? I need to learn how to service it, especially if there's something that needs adjusting or lubricating right now.

fietsbob

Pull it apart, remove core, clean off the grease, in solvent,

then go to an ATF dunk lube.. plan on doing it more than once..

its lighter, so will drag less..

mc510

You mean clean the grease off the internal mechanism, but keep grease on the external bearings, right?

I see a lot of YouTube videos showing how to do that for an Alfine hub, is it the same for an Inter-8 hub?

Andrew R Stewart 

First thing I think of is chain tension, which is of course no tension. The chain should have a small amount of looseness or it will pull on the cog and therefore the hub's internals. The result of a too tight chain can feel much like that of too tight bearings, because it's really the same effect. Andy

fietsbob

Alfine 11 is made with oil in mind . you have fill hoses to screw in..

My Rohloff uses a flushing oil that is sucked out after a while , then re oiled.. thru a hose . hypodermic

Alfine 8, is as I understand a Nexus 8 core, with a disc brake mount casing..

as far as axle bearing greasing, I have greased them on my S-A AW 3, and oiled the internals

Through axle, hollow for shift chain ...

Generalizing ; I don't have a Nexus 8, do have a Sram 9, no sticky freewheel issues...




....

sweeks

Seems a little early in the hub's life to be needing service. As far as service goes, I agree with Fietsbob about the ATF dip. I have 2 Nexus-8 hubs and 2 Nexus-7 hubs, not all in service at any given time. But one of the 8s has about 10,000 miles on it and runs like new. Once a year I open it up and dip the gear cluster in a container of gear oil. I used to use ATF, but the gear oil is slightly more viscous and I like it better (personal opinion). I never cleaned the grease off the hub, but over the years, the grease has gone away. I *do* place "official" Shimano Nexus grease on the wheel bearings with each service. The Nexus grease appears to be some kind of molybdenum disulfide compound. Over the course of the year, the bearing grease gets washed out by the gear lube to some extent, but the bearing races remain unblemished.
BTW, the wheel spin looks pretty normal to me. Of course, my wheels are 20" so they probably have less momentum. As mentioned ^^ make sure your chain has a small amount of slack in it.
Hope this helps.

mc510

It's been like this from day one, not something that's developed after 250 miles.
Chain has some nice slack in it, I corrected that immediately after purchase.
I'll try the oil dip as soon as my clip-spreading pliers arrive; sounds like it might help and can't hurt. I wonder if the cones are also too tight; oil dip will give me an opportunity to adjust those properly.
Thanks all.

sweeks

I don't remove any clips, though I have done and it's not difficult. I simply open the non-drive side of the hub by removing the locknut and cone, then pull the innards out and dip the whole assembly. It's a pretty quick process.

Andrew R Stewart 

I tend to agree with the shop wrench to a degree. I've found that many of the modern crop of IGHs do have more drag/friction then external geared hubs do, or for that mater then old generation (SA AW, Shimano 333) hubs do.I wish I was more fluent in modern IGHs so I could tell what was the norm. in running freedom. Andy

Dan Burkhart 

Watching your video, that does not look like an unreasonable amount of drag. Note that the hub is not carrying the chain forward as it freewheels.
One common source of friction with these hubs is between the cog and the dust ring. Nothing but wear will improve that.

mc510

Thanks, I guess the directions that I've been reading have been over-complicated. I just did what you described and it was as easy as you said. I went up through step #5 here https://www.sheldonbrown.com/nexus8/pages/13.htm ; is that where you stop disassembling and then do your oil dip? I wasn't set up to do the oil dip today, so just put it all back. The cones seemed a little tight to me, but reassembling a hair looser didn't change anything. As everyone is saying, I guess this is what this hub is like.

Yeah, I was expecting something more like the SA AW3 that I've been riding for the last 25 years, but (not surprisingly, I guess) there's a price to be paid for the five additional gear ratios in the Nexus

Joe Bikerider

sweeks

I'd say I stop at about #6 normally. I like to take off the right-side dust cap to service the large bearing ring. I have gone as far as #10 , but this isn't necessary IMO for routine service.

I started using a giant beer mug for the dipping process, but the axle prevents the gear clusters from being immersed unless the mug is pretty much full. So I constructed myself a container that has a tube sticking out of the bottom for the axle. This is made out of a "Talenti" ice cream jar with a plastic syringe (the tube) epoxied to the bottom. The axle drops into the syringe, and a whole lot less oil is required. I just leave the oil in the jar and top it up as needed; the debris settles out into the syringe which has a screw in it for cleaning if I ever feel like it.

The "official" Nexus grease I've bought is black and appears to be a molybdenum grease. One of my Nexus 8-speed hubs (the "Red Band", IIRC) had a white grease resembling lithium grease the first time I opened it. I just dip this hub. The reason I went to gear oil instead of ATF was for the leaking issue. I didn't have much of this problem if I let the hub "drip" for a while after dipping. The gear oil stays on the gear clusters better than ATF. Also, I am using the same gear oil as my Alfine 11. It's a synthetic oil, much less expensive than the "official" Shimano oil, but still$24 a liter... that's why I don't dump the oil after each dip.



Oiler on its convenient "stand"!


Syringe serves as relief for the axle.


Close-up of the syringe. Some settled debris is seen in the bottom.

mc510

Nice @sweeks, just found an old syringe in the garage and am going to make up a container just like yours! I'm actually not a huge fan of Talenti gelato (texture seems a little over-emulsified for my tastes) but I'll figure something out. I have a quart of Lucas 75W-90 100% synthetic gear oil that should be suitable, no?

sweeks

Should work!

paulb_in_bkln

I had a similar question (which is I why I found this thread). I opened, cleaned, and regreased my five-year-old Inter-8 using Shimano's runny grease. There's probably nothing wrong because the hub shifts perfectly and is very quiet. But, I've also noticed that, while coasting, a lot of rotational motion is transmitted to the pedals, carrying them forward very vigorously. And there's quite a bit of friction while backpedaling. The left side bearing isn't too tight, for sure. I don't remember what it was like before I did the service. Could it be the dust cap? It seems to me if something was out of whack inside, the hub wouldn't be shifting correctly and running so quietly.

Dan Burkhart 

Are you sure you didn't get roller brake grease? It is black, but the lube for the Nexus hub internals is white.

paulb_in_bkln

This is positively true. White and runny. Comes in a tube.

paulb_in_bkln

BTW, I saw this website from a Seattle bike shop about how Shimano doesn't put enough grease in the hubs and if you ride it in the rain in no time you'll have the corroded, pitted piece of junk they show in photos, and recommending frequent overhaul. After five years all weather riding on mine this had me scared out of my wits.So I opened the hub and.... it was fine. I cleaned it up with mineral spirits and through a magnifying glass I couldn't find a trace of any damage. I regreased it with the Shimano stuff and apart from the backpedaling friction I mention above it seems to be working perfectly. I think it could go another ten years without any worries, assuming I don't ride it into the ocean.

sweeks

There must have been a switch sometime. I got my first Nexus hub (7-speed) in 2003 and serviced it soon afterwards. I looked far and wide for the "special" grease, and eventually found some. It was black, as I described earlier. In 2006 I got a bike with a Nexus-8 hub ("plain", not "Red Band"). This hub also was lubricated with a black grease. When, shortly afterwards, I acquired a "Red Band" Nexus-8, I was surprised to find the white grease (like a lithium grease) inside. Now, all these hubs get a "dip" in gear oil at an appropriate interval depending on how much I use the hub. The black grease is placed on the hub bearings.
Attached is an image of two greases: Roller Brake and Nexus hub. There's a small smear of each grease by the nozzles.

Shimano Roller Brake Grease and Nexus Hub Grease

sweeks

LoL! On the label: "Volume: 100g"

paulb_in_bkln

Great catch! I hadn't noticed that!

paulb_in_bkln

Perhaps Shimano made the switch in color to avoid confusing the two products.

Winfried

Hello,

I'd like to dip this SG-8R31 Nexus 8 into gear oil to see if it makes it less draggy, but am stuck removing the core from the hub: It won't come out.

Should I loosen something on the drive side?

Thank you.


---
Edit: You just have to hit the axle more strongly :-p

DONE.

sweeks

Be sure to clean all the grit off before you dip it.
Grease the bearings and adjust for *zero* play... easier than with a quick-release hub. There's always going to be some drag though... lots of little spinning gears!