Is my Nexus hub dead?

[mark a.]

My Nexus 8 red-band (model SG-8R25) was feeling rough. Since none of the bike shops around here are keen to deal with hub gears, I manned up and took it apart, with help from hubstripping.

My skills run out about here, though. Is my hub dead? Here are the internals straight out of the shell:



I'm going to take a wild guess and say that brown (and especially brown liquid) isn't what I want.

Here are the internals and the inside of the shell after a quick wipe down with a rag:




Can I do anything from here? I don't particularly want to strip the hub down any further. Can I just give it a further wipe and add a load of grease? Or with that much rust - especially on the bearings - is it dead? The middle ring of the shell looks decidedly brown and possibly pitted, which could be terminal.

Any help would be most appreciated.

p.s. I've already had the rear wheel and hub replaced twice by Halfords (it's a Carrera) under warrantee. I'm not entirely sure if this hub is new or if they have "repaired it" themselves.

p.p.s. sorry about the huge pictures. Photobucket has changed so I can't find the resizing options any more.

[BeeKeeper]

If it is just "rough" and not actually broken, in the sense of something has snapped then it might be possible to get it to run on for a bit longer, but I suspect the bearing surfaces are pitted and it will never be the same again.

I don't think you will lose anything by simply trying to de-grease it as much as possible - i.e. an overnight soak in something like Gunk, although you could use paraffin. You might even be able to persuade a local company to clean it for you if they have suitable facilties.

You then need to try and remove as much of the surface rust as possible from the bearings then re-assemble, and I would fill it with oil rather than grease then take it for a run and drain the oil out, re-fill again and you may need to keep repeating this until all the loose rust has been dislodged. As the seals are probably shot, which is how the water got in, you will probably have to re-pack with grease at the end on the assumption any oil is likely to leak out.

[Brucey]

your hub is in a 'typical' condition for one that has seen a couple of winters (or summers.... ) and not quite enough maintenance.

Comments as follows

1) Your hubs isn't quite scrap yet

2) Dont worry too much about a little corrosion on the centre shell band; this is just for the roller clutch to engage with IIRC

3) the rumbling is most likely from the large ballrace. It will probably rumble (and keep working) for years, but there is a risk that the clip will break up.

I'd suggest that you clean and grease everything you can get at, add a couple of spoonfuls of gear oil, and whack it back together.

After a few hundred miles open it up again and take a look at it; clean and regrease as necessary.

In the meantime keep a 'weather ear' open for any unusual noises that might indicate that the clip is breaking up.

It may not be a bad idea to replace the clipped balls with loose balls (you will need loads...) if they are in a bad state; even with a new ball clip in there, the rough cup and cone surfaces make it more likely that the ball clip will snag and break up.

You are probably fortunate that you caught this when you did; another month or so and it would have been scrap, as it is you have a fair chance of saving it.

In the long term I'd suggest either a repeat stripdown of this kind once every six months, or (easier) adding a lube port to the hub shell, and treating the hub to regular shots of a semi-fluid grease. The stuff meant for land-rover front swivels is good. The excess will come out and make a terrible mess for a few days but it will keep the hub happy inside.

hth

cheers

[Meshuga]

The 8R25 hubs didn't have very good seals. That hub has had water in and I think it will take some work to get it going again as Brucey says.

The 8R36 hubs have better seals and are the same internals and seals as the alfine 8 speed. The hub shell is pitted so I would go with a new hub and get it built in if possible. Otherwise the internals from the new hub can be slotted in without the rebuild as I believe the shells are the same. If it is a Carrera you'll need the Nexus with the roller brake fitting. Rose bikes have the 8R36 hub, sprocket, shifter, cable and new cassette joint for £110 delivered to the UK. You should be able to find someone to build it into the wheel for £30-50, unless you are happy to do it yourself.

[7_lives_left]

A word of warning. I had (still have) an afline hub that was in a similar state when I serviced it. I bought shimano nexus grease to re-lube it. I didn't have the specialised tools to dismantle the inner workings and some of the gear rings/pinions are /hard to see/get at/. What I did was introduce the grease onto these gears using a small bladed pen knife as a pallette knife through a gap. There was already grease there but I though adding a little more wouldn't hurt. This turned out to be a bad move. As well as the gears, there are also some pawls hidden away inside. In adding the excess grease I also got grease on the pawls, not that you can see them. This made the pawls stick so that they wouldn't engage properly. The effect was that when changing from gear 4 to gear 5 the pedals would spin freely without providing any traction until the hidden pawls managed to engage. This isn't desirable in a hub gear, especially is you are standing on the pedals.

Shimano's recommended method of lubing the hub is to dunk it in the special oil. I think I found out why this is so the hard way. That's how I will be treating the replacement hub anyway. If you do decide to regrease it, don't use too much. And use the right sort of grease too.

[mark a.]

Thanks for the help. I'll try and save it for now. If nothing else, it'll be good practice.

It's now my town bike, so isn't used that often nor for any significant distance. So it doesn't need a service purely on miles - or so I thought. Brucey's right in that it's probably about 2 years old. The grinding has been a few weeks of light use and most noticeable while freewheeling.

There goes my theory that these are essentially maintenance free! (My wife has recently bought a Rohloff bike and that will definitely get its oil changed regularly.)

Should I get the official Nexus grease? IIRC the official Shimano oil bath costs a million pounds and is really for workshop (re)use. What oils do people recommend? I've heard automatic gearbox oils, the LR stuff that Brucey mentions and probably a few others. But oils and grease are a mystery to me, so I can't really wing it.

Thanks for the tips on not overdoing the grease, 7 lives.

If my repair doesn't work, I'll probably bin the hub and get a cheap 3-speed since it's only my town bike. To get an idea, do you think I should stick with Shimano or get a Sturmey (new or used)? Longevity is the main aim, and it will need to be roller brake.

[7_lives_left]

Should I get the official Nexus grease?

I don't know. It does have to be something that will cope with the extreme pressure. I would avoid degreasing it myself so you keep the original grease. If you have some graphite grease I would use that (it's a dark black). The original nexus grease was black and tar-like consistancy. SRAM do a grease for their hub gears that also has graphite and Moly disulphide in it so I have read. The current nexus grease is white and has PTFE in it. I think it comes in a tube with about 100ml in it and costs maybe £20 ? Not sure of the volume, the label has fallen off mine.

IIRC the official Shimano oil bath costs a million pounds and is really for workshop (re)use. What oils do people recommend? I've heard automatic gearbox oils, the LR stuff that Brucey mentions and probably a few others. But oils and grease are a mystery to me, so I can't really wing it.

I have a shimano oil bath which I purchased at the same time as I got the replacement hub. I haven't used it yet! I could maybe send you some oil in a film canister. Send me a PM if you are interested.

[Brucey]

Re the lube; I suggested grease plus gear oil; this is a 'DIY semi-fluid grease recipe'. The LR grease has all kinds of solid lubricants in it for severe loading, and is a semi-fluid grease anyway. Neither should gum the pawls up, unless we have Siberian winter... I don't see the need for the shimano oil dunking kit TBH.

Older SA gears needed a little oil once a month and would last for years, but modern SA hubs (despite being no better sealed) are greased and are not designed to be serviced without opening them up.

A sturmey archer X-RD3 is a three speed with a nice reliable hub brake; this might do the trick. They do a less expensive steel shelled version too. Adding a grease port is possible but the problem is that excess lube will get into the brake unless an additional seal is installed near the LH bearing. Fortunately an 'O' ring can be installed for this purpose without too much difficulty.

The older AB hub is stronger internally (in some incarnations) but won't necessarily have the correct width to fit a modern frame.

Any of the hub gears under consideration can be converted to use a grease fitting and will work OK with a semi-fluid grease inside them. This can be added using a standard grease gun (I suggest using a Wanner/Wanner-Abnox gun if you want the best) through a suitable fitting. Once a month, takes about 10 seconds to do; it is hardly onerous. Although it is a bit messy, as long as there is stuff coming out, chances are that water isn't getting in....

cheers

[mark a.]

Thanks again.

I have some of this grease in my bike box:


Will this be ok to use, since I have it anyway? It's obviously ok for the bearings since that is what it's designed for, but I don't want it to mess up other internals. Otherwise I'll get the official grease.

Unfortunately greases and oils still confuse me, so apologies if it's like talking to a 5 year old. When you say gear oil, do you really mean a bottle of Castrol used in cars?

The rideyourbike website uses Phil Wood Tenacious Oil and "blue marine grease", but I think that needs a full strip to individual components.

I am learning, so thanks again for your help.

[breakwellmz]

Hi.

I don`t know if you have been unlucky,or i`ve been lucky

Have you read this?-

viewtopic.php?f=5&t=65217&hilit=+leave

Cheers.

[Brucey]

re gear oil;

it is sold badged as 'gear oil'. EP90, Hypoid, GL4, GL5 specifications. The higher the viscosity number the better; a 90W gear oil is fine but you can also get 130W which is probably better for a hub gear.

The finish line grease is OK for gears etc (perhaps not as good as a proper gear lubricant) but it is better for bearings and quite expensive, so I'd save it for that.

Many automotive greases (and the Finish line grease, probably) come with an NLGI grade of about '2'. This is too thick for pawls in hub gears (and freehubs) especially in cold weather, hence the suggestion of adding oil with the grease to make a lubricant of a more runny consistency, using readily available ingredients. The stuff that usually goes in hub gears is ~NLGI #0 or #00 IIRC, and you may well not be able to buy grease of this consistency in your local car spares shop at all, and even if you can, it won't have all the solid lubricants etc in it that make the original Shimano lubricant black from the start.

cheers

[mark a.]

Hi.

I don`t know if you have been unlucky,or i`ve been lucky

Have you read this?-

viewtopic.php?f=5&t=65217&hilit=+leave

Cheers.

Ooh, I hadn't read that before. Thanks the the link as it's answered some more questions. I'm glad yours was more successful than mine!

Thanks once again Brucey. You have been very helpful and patient with me being thick!

[breakwellmz]

Hi.

We are/were in the same boat there re lubricants.

Between you and i,that Brucey is a little gem

Good luck with it.

Cheers

[breakwellmz]

re gear oil;

it is sold badged as 'gear oil'. EP90, Hypoid, GL4, GL5 specifications. The higher the viscosity number the better; a 90W gear oil is fine but you can also get 130W which is probably better for a hub gear.

cheers

Hi.

I didn`t realise you could get gear oil THAT thick.

I`ll admit to expecting the EP90 is used to be `thicker`than it was.

Cheers

[Brucey]

IIRC 130W gear oil is what is required for the final drive on one of my old outboard motors. I'm pretty sure you can get thicker gear oil that that, even.

cheers