Kreuzer

1.5 years ago I bought 8-speed Shimano Nexus hub, shortly after I bought new city/road bicycle for daily commuting.

I became concerned when read on Sheldon Brown's website that these internal gear hubs are improperly lubricated for wet climate. I live in Ireland, and it's very damp here, it rains quite often. Another complication is that my bike is stored inside my house, in a heated space, so when I bring it outside every morning, the air inside the hub obviously contracts as the hub cools down and moisture together with sand and dirt can get pulled inside. This risk is very real since Nexus hubs aren't sealed well, compared to Alfine hubs, for example.

Therefore I followed Sheldon Brown's advice and properly lubricated my hub, in order to prevent water and dirt contamination in future. I did it in January 2015 right after the hub was built into my bike's rear wheel by LBS. First, I removed manufacturer's grease using special spray, allowing hub's parts to dry after that. Then I applied Phil Wood waterproof grease for the outer bearings, white lithium grease for the gears and Phil Wood Tenacious Oil for the pawls and in the hub shell 'to slop around', just like you can see on this photo:

https://www.rideyourbike.com/images/i.../alfineoil.jpg
(picture taken from here) (actually you can see marine grease applied too, where left side outer bearings will sit)

During all 1.5 months of riding (3-7 times per week, making 2 * 6 km trips) I continued having two issues.

First issue is a gear slips now and then (I get sudden 'idle' turning of my pedals for like half or their revolution). It can happen once during my 6-km trip, it can happen twice, or not happen at all. There's no difference which gear is on now. It's especially frustrating when it happens as I'm accelerating standing up on my pedals (and it's always accompanied by four letter words). I know that gear isn't there 100% and this is very discouraging. This makes me in-confident and I don't commit to my full power efforts while riding.

Is this normal? I read somewhere on Amazon, in comments, that a Shimano hub can 'skip' a gear now and then (suddenly go up or down one gear, as I understand), but this is supposedly normal "until the unit 'beds' in". Does this mean that slippage, which I'm having, will also go away when the unit 'beds' in? Did anyone have such experience?

Second issue is the sound I hear on 4th and 6th gears. It's like grinding or something, not too strong as sound, more as vibration I feel with my feet. I am also wondering if this is normal and if it will go away too.

Like I said, I've been riding my upgraded bike for 1.5 months, 5 times per week in average, making 12*5 = 60 km per week. So it's like 60*6.5 = 390 km (242 miles).

Can this slippage be because my rear wheel is a bit askew after hub's installation? Unfortunately, I couldn't manage to correct it, no matter how I tried, even though dropouts are vertical. I didn't have this issue when there was a regular Shimano Altus derailleur...

FBinNY 

You have an IGH hub with vertical dropout. Do you use a chain tensioner, or did the chain just work out right? If no tensioner, is there some slack in the lower loop?

Also do you have the right keyed anti-rotation washers, and do they key to the dropouts properly, with everything aligned?

How and why is the wheel not aligning right, is the axle width wrong, or is something in the way?

If everything external is right, and given that you've opened the hub once already, I'd open it again and see if there's anything obvious such as migrated grease making the pawls sticky, dirt where you don't want it, or any chipped parts or metal chips in the oil sump.

Reynolds 

Don't know about the slipping, but I have a Nexus 8 with 13000 kms and it always felt like grinding in 4th gear. No problems so far, Shimano says it's normal to hear noises in all gears in certain circumstances: SHIMANO Dealer's Manual / User's Manual

Kreuzer

Old chain tensioner from the original rear derailleur (Shimano Altus) is still there. Otherwise I would need an eccentric bottom bracket to adjust chain slack.

Yes, I bought them separately, and I think so, I didn't notice anything unusual at least, looks fine.

Well, firstly, there was a little too much width between two dropouts, I had to tighten the end nuts to remove that extra width. Secondly, there's a difference compared to the old hub. The axle is not round (it has a specifically shaped cross-section, for use with anti-rotation washers), and its axle's orientation inside the dropouts is almost vertical. Hence there's a bit of freedom, the axis does not sit naturally straight in the dropouts, if you know what I mean. But another problem is that the wheel seems to be offset to one side, I judge by its orientation relative to the mudguard. It wasn't like that before IGH was built into it... And again, no matter how I tried, I couldn't really align the axis in the dropouts so that the wheel is at least straight while being offset...

I'm not really experienced in this, so a question which arises in my mind is: will I have to remove previous grease and oil (if there's no dirt inside) in order to make a second attempt in lubricating the hub? Or I will just have to, say, add extra grease and possibly oil, if there's no grease around pawls?

Do I understand it correctly that probably the pawls simply get stuck in free rotation mode sometimes, which normally happens only when back-pedaling?

Kreuzer

I have a bike with 7-speed Nexus since 2007, no lubricating, no servicing, no problems...
Although, to be honest, I never rode that bike so regularly, more like once or twice a year for couple of weeks, and rest of the time it's stored in a garage.

Dan Burkhart 

No doubt in all your investigation, you have learned that precise shifter adjustment is critical with these hubs, as is free and unfettered movement of the shift cable in the housing. Issues with either of these can cause the problems you describe.
Also, in lubricating the internals with regular lithium grease, you have introduced another problem. The internals need to be lubricated with a semi fluid low viscosity grease, or better yet, with oil.
The reason for this ties in with the necessity for accurate adjustment. In gears 2,3,4 and 6,7,8, shift pawls rise from the axle to couple sun gears to the axle. If the grease lubricating the actuating arm and the pawls is too stiff, it can prevent the pawl from fully extending and completely engaging the ratchets on the inner circumference of the sun gear, which is also what happens when the shifter is slightly out of adjustment. Incomplete pawl engagement will result in skipping.
So, if there is heavy grease in the actuating arm and shift pawls, I would wash it out with solvent and give it a oil dunk lube job, (I've done it successfully with ATF) lube the outer bearings with wheel bearing grease, ensure proper shift cable adjustment, and ride.
Before too many seasons pass, you will have to dig in a bit further to clean and lube the drive side cone, but that's another discussion.

Mr IGH

The Phil Wood oil is too thick, use something thinner such as ATF.

Kreuzer

I never said I have any shifting issues. Shifting between gears works fine.

I didn't add any grease of any kind to the pawls, I used oil type recommended on Sheldon Brown's website. What's 'actuating arm'?
Why can't I use white lithium grease for the gears if that's what they were lubricated with initially?

Which part of hub is that exactly? What's complicated about cleaning and lubricating it?

Is this or this an ATF fluid?

Kreuzer

Off-topic:

Is there some way to remove coaster brake parts from a 7-speed Nexus Hub? I don't want to use this kind of brake on my old bike anymore, but also I want to oil it properly like I would a regular hub, without using special high-temperature grease.

Dan Burkhart 

It's entirely possible for shifting to seemingly work fine with the shifter out of adjustment but the pawls will not be fully extended for complete engagement.

https://www.youtube.com/watch?v=x_Gn...GZxhd1WdyVTi-h


The original grease was white, but it was a semi fluid grease, not your garden variety lithium grease.



https://www.youtube.com/watch?v=Nsn8...GZxhd1WdyVTi-h

Kreuzer

You're talking about those alignment marks (yellow in my case). Well, I know about them and did the necessary adjustments previous time. Thanks for reminding, I'll make sure that they are aligned next time too (and I'll check regularly that they keep aligned).

I used this one. Is it so bad?

I just read on Aaron's Bike Repair website (at the bottom of this page) that they don't use any grease for the gears (ah, I obviously messed up, relying solely on Sheldon Brown's advice), they use Phil Wood Tenacious Oil instead, which they also apply to roller bearings and to the pawls (I applied it to the pawls too). Moreover, they say Do not use heavy grease on the rollers or the hub may slip but I think I used lithium grease for roller bearings, hence possible reason why my hub slips... am I right?

I've opened up my hub again, you can see some photos below (click to enlarge):



White lithium grease that I initially applied to the gears and roller bearings is mixed with oil now, I really don't want to clean everything using solvent and lubricate gears anew using Phil Wood's oil (I don't have much of it left), so what I'm going to do, I'll remove as much grease as I can using cloth and add more oil instead, and add some of it into the hub's shell again (as seen on this picture), this way I think I'll at least reduce the proportion of lithium grease relative to tenacious oil. Do you think this might help? I'll also add more waterproof grease to the outer ball bearings, because I don't think I used plenty of it last time, which is recommended for a good seal.

Thanks Dan, that's indeed for some other time... I don't have that tool anyway

Joe Minton

Dan Burkhart is the man you should listen to, he knows of what he speaks.

I have been running a Nexus 8-speed hub for 2.5 years and have ridden it about 3000 miles in that time. After the first six months or so, I dismantled the hub and changed from grease to oil. I use a rather thick synthetic ATF (Red Line racing ATF) that closely matches Shimano's own gear oil for viscosity. I believe that shimano now uses its rather preciou$ oil in all its hubs.

I've had no trouble whatsoever with shifting, slipping, leakage, etc. The hub functions as it should.

It is geared lower (higher numerically) than recommended by Shimano (38T front 23 rear). However, I treat it fairly gently; no jumping off curbs, stomping while standing or shifting with anything more than a light load on the pedals.

Many folks have been running ATF in these hubs with apparent success. Your jumping problems would mostly likely disappear with the use of the lighter oil.

These hubs aren't well sealed like many other Shimano hubs. I use Red Line synthetic grease, and a lot of it, in the bearings and under the seals outboard of the bearings. The grease presents a reasonable barrier against water entry.

None of these hubs should ever be immersed. If that were to happen to mine, I would dismantle it to be sure no nasty stuff had gotten inside.

Joe

Kreuzer

Joe, I am listening to Dan. It seems you didn't read our dialogue attentively.

Using ATF instead of oil seems to me like something not proven safe yet. This video by Dan has this in its description:

Obviously he is not 100% sure that ATF should be used for these hubs.

I don't want to experiment, therefore I would rather stick to proven solutions, ok? Aaron's Bicycle Repair guys have enough professional experience and certainly wouldn't recommend using Phil Wood Tenacious Oil for the gears, pawls and cone bearings, if it wasn't optimal for Shimano hubs.

Mine was 48T front 21T rear, I'm going to swap rear for 19T ring now (I've got both). I want it geared close to when I had 7-speed rear derailleur. 21T is not enough for that.

I do jump off curbs sometimes, but carefully and slowly. But I try to never shift while turning pedals (sometimes it happens unintentionally).

I want first to hear Dan's feedback on my assumption that this might be caused by lithium grease around cone bearings and gears. If he'll confirm, I'll re-lubricate the hub as described above.

I know that they aren't sealed well, that's why I use Phil Wood waterproof grease for outer bearings, and under the seals outboard of the bearings, like you do.

Immersed in what?

Joe Minton

water -- thought that would seem obvious.

AnkleWork

Then why not just stick to Shimano's instructions?

FBinNY 

Too late now. The OP chose to take the advice of kibitzers who had "better advice" than the factory. Now he's going to more kibitzers to remedy the situation.

Who's to know if his problem is related to what he did before, or something else, but now he has little choice but to move forward. IMO- he should open, clean, inspect and relube according to factory guidelines (oil) and use that as a baseline to see if there might be other issues.

Dan Burkhart 

Lithium grease will not hurt the bearings or gears, the problem is that a stiff grease will not migrate into the planetary gear shafts which need lubrication too. If your hub is the base model, those shafts do not have roller bearings, whereas the premium (red band) version and the Alfine hubs do. Either way, they require lube which only a semi fluid grease or oil can provide.

Joe Minton

anklework, FBinNy, Dan Burkhart
--- Amen

Joe

Kreuzer

Nice.

Not obvious. There are other options. Oil, kerosene, citrus solvent, etc.

SORRY, I'M A NEWBIE, I didn't find Shimano instructions on how to lube the hub properly for wet climate. Instead, I found instructions on Sheldon Brown's and Aaron's Bike Repair websites. Not everyone is as experienced as you are!

https://www.rideyourbike.com/images/i...nexus8rust.jpg
https://www.rideyourbike.com/images/i...manonexus8.jpg

Internal Gear Hub Service

I'm a daily commuter in damp and rainy Irish weather. I don't want to risk having to buy a new hub after riding few years with cheap manufacturer's lubrication inside the hub.

Dan, thanks. I thought doing this will ensure that the parts where grease didn't get to, will be 'washed' by this oil...

My hub is SG-8R36, how to check if it's the base model?

Could you please comment the photos that I published? I didn't find anything strange inside, except oil together with grease made a weird coloured mixture and marine grease around outer bearings on non-drive (left) side became grey (but around opposite bearings is still green...).

AnkleWork

Nothing to do with experience, but speaking to your statement about experimentation. I mean this as friendly advice: pick a lane and stay in it -- either experiment or don't.

FBinNY 

My point in referencing kibitzers was that one should give great weight to manufacturer instructions. They made the product and usually know best how to care for it. That doesn't mean one shouldn't be free to go other ways (I'm a repeat offender) but one shouldn't go another way without understanding the implications.

You say, you were concerned about performance in the wet, which is legitimate, but without knowing that there was in fact an issue (ride a while and find out), and without understanding the properties of lubricants -- things like whether they flow well or not --, and/or the mechanical needs -- where lube is needed, pawl spring strength, etc. -- one is working blind. Without understanding as a basis for making decisions, it's like driving when lost with your mother and mother-in-law in the back seat giving directions.

There'll always be a large spectrum of opinions on any bike related issue, it's the nature of the business. But you need to have a way to know who to trust, and in the final analysis, the factory should be the default.

In a way, your situation is like that of a doctor seeing a new patient on a number of meds and with a hard to diagnose condition. A standard method is to carefully withdraw all the meds, and see what's what, then to administer only those needed. In your case, I might have suggested axle flex (based on your reports of alignment and dropout issues) as a possible cause, but there's too much clutter in terms of lube or adjustments, so I suggested going back to square zero and moving from there.

Kreuzer

I said I don't want to experiment. I want to do the same as professionals in bicycle shops do for tens or hundreds of hubs, for which they are getting paid or not paid if it doesn't work (this ensures they stick to efective solutions). I don't want to do anything that just MIGHT work, I want to do something that WILL work.
If you haven't noticed, I am 'staying in a lane', regardless of conflicting advice that I get.

Dan Burkhart 

You have the premium model. Don't have time right now, I'll take a closer look at your pictures later.

Reynolds 

I drilled an oil port in my hub and injected 20ml ATF on it, drained and refilled every 5000km or so. I'm hoping the ATF reaches the drive side cone - it's not sealed from the rest of the hub, and as there are small leaks to the outside, not drops but rather an oil mist, probably the gears stir the ATF enough to get to every place on the inside. What do you think?

Kreuzer

Thanks, FBinNY.

Presence of such issues simply reduced weight of manufacturer's advice in my eyes.

I don't know about you, but I'm a kind of person who would do something to prevent an issue rather than wait until it happens and it might become too late to do something about it.

I know who to trust — mechanics who deal directly with issues their clients have, in contrast to manufacturers who only makes their product and not always know all the nuances of maintenance.

But consulting with people on a bicycle forum just helps thinking process, I never take such advice as unquestionable and self-sufficient.

Wrong, I understand how different lubricants work - otherwise I wouldn't have made a 'puddle' of oil inside the hub's shell, which I did specifically so that lubrication gets into all parts of the hub, including those not covered by too viscous lithium grease.

Could you please extend on axle flex topic for me?

Dan, take your time, there's no rush. My bicycle will stay disassembled for 3-4 days anyway, until I get the new tyres that I ordered online.