IGH lubrication; a smoking gun.

[Brucey]

IGHs are still by far and away the most practical kind of variable gearing for utility bicycles. After experimenting with ball bearings, roller bearings etc on the planet pinions, the vast majority of simple IGHs use plain bushings on the planet pinions. Despite this, even simple inexpensive IGHs can still be both durable and pretty efficient, provided they are correctly lubricated.

In the UK the ubiquitous SA three speed gear was fitted with an oil port for about 80 years or so. In exchange for the slight effort required to add a few drops of oil through the hole once a month, an SA three speed gear could reasonably be expected to last a lifetime of commuting or pottering about in all weathers. As the excess oil comes out of the hub, it is likely to carry most of any dirt, water, rust, & wear debris particles with it, thus keeping the internals in good order. These hubs are so long-lived that isn't uncommon to find that the only salvageable part on an old rusty bike is the SA 3-speed hub.

Then, about 25 years ago, someone decided that the hole and the little plastic cap that went into it were clearly a needless extravagance, and that it would be OK to lubricate the hub using a grease of some kind instead. And you know what, they were right. It works just fine, for a while.... But ever since that time it seems more likely that such hubs fail in new and interesting ways; and after a year or so the condition of the grease is liable to be suspect, and of course there is no flushing action of any kind.

Ironically enough you can still add oil to a typical SA three-speed; but it takes a little more effort. You simply select top gear, unscrew the indicator rod, and dribble the oil in there instead. Just go easy with a brake hub; if the oil gets into the brake it won't work at all well. However other IGHs (eg with rotary selectors) are not so easy to keep happy.

As well as all current SA hubs, all Shimano (except for Alfine 11) and all SRAM IGHs are grease lubricated. They appear to use various different greases. SA use something that looks and smells like Castrol EP-00 semi-fluid grease, and SRAM use something that looks similar, but is slightly thicker. These greases eventually separate somewhat; this leaves a soap with less oil in it in some places and an oil with less soap in it in others. On the minus side this leaves blobs of dried grease (soap) that can eventually cause problems, but on the plus side the oil will tend to work its way around the hub to some extent before it leaks out. In practice a shot of grease like this can be OK for a year or two provided nothing inside the hub is wearing, and the water doesn't get in.

Shimano have used 'black grease' and 'white grease' inside Nexus hubs. These greases are a fair bit lot thicker than either SRAM or SA grease, and there is little sign of any separation with either type; I've never seen any liquid oil inside a shimano hub that has arisen from grease separation. Nonetheless the grease fails after a while; it still dries out and it gets pushed away from where it is meant to be, never to return.

A common failure mode in these hubs (and SRAM ones) is for water to enter the main ring bearing and this will fairly quickly kill the hub outright in a short while. Because (unlike most conventional SA hubs) the bearing race is machined into the hubshell, if this bearing is damaged a new hub centre won't be a full repair.

A second common failure mode in these hubs is that the lubrication fails on the planet pinions. These turn all the time you are pedalling (in any gear) and they see substantial loads in every gear other than a direct drive gear. To give you an idea;

Three speed gear (all makes); 2nd- No load, 1st and 3rd, loaded.
Nexus 4 speed gear; 1st gear -No load, 2nd, 3rd, 4th gears, loaded.
Nexus 7 speed gear; 1,2, 6,7 - Load on half of the planet pinions. 3,4,5 - Load on all planet pinions.
Nexus 8 speed gear; 5th - no load, 1, 6,7,8 -load on one set of pinions, 2,3,4 - load on all pinions. [NB 'red band' models have roller bearings on the pinions instead of plain bushings]

Just comparing three speed hubs; SA ones usually have four chunky pinions riding on large diameter bushings of ~1/4" (6.4mm) diameter. Shimano also have four pinion gears but they are narrower, set onto a smaller bushing (~5mm dia) and also set onto a smaller working diameter. Overall the bushing loadings are about 50% higher or so than in an SA hub. SRAM (and previously Sachs) 3s hubs use a similar arrangement to shimano but this time there are only three pinions, not four. Loadings on the bushings are about double what you will see in an SA hub.

The pinion bushings in N4,N7,N8 hubs are similar in diameter to those inside N3 hubs. Even though they are set onto a larger diameter, they still wear. The photo below shows what happens if the grease fails inside an N4 hub;

three little piggies; (no brick house here)

The numbers below each gear show the measured play in the pinion bushings (in mm!). The wear in all cases is mostly on the pinion, with rather less on the pinion pin. The brown staining on the two most worn is from corrosion. Notably the least worn pinion bushing is also the least corroded/brown stained, and still had the most grease on it. The most worn pinion pins have clearly been rotating in the planet cage for at least some of the time, since they are worn on the ends too; this is not usually seen in well lubricated hubs. It is presumably no coincidence that the teeth on the gear with the most worn bushing are also damaged; it isn't clear in the picture but there are about eight teeth from one gear that are about half the usual height. The shrapnel thus generated had trashed the rest of the hub pretty well too.

This shows very clearly that the shimano grease isn't mobile inside the hub and probably isn't uniformly applied in the first place either. Although there was some corrosion on the planet pinions, this was the only part of the hub that was corroded; the small amount of water inside the hub arising from condensation would be enough to cause corrosion if the grease film were breached, and this seems to be what has happened.

I've seen similarly accelerated wear on the pinion bushings in N7 and N8 hubs, too. In fairness this is usually seen after a few years of use but if water (especially salty winter water) gets inside the hub everything can fail in a few weeks. I don't believe that shimano's oil dip procedure is truly effective, because a) it generally doesn't get done often enough, and b) most of the wear debris is liable to stay inside the hub, causing yet more wear and damage.

So what to conclude? I'd suggest that if you don't do anything else, regularly adding oil to a 3s hub via the toggle chain/pushrod hole (most N3, SRAM 3s, most SA 3s hubs) is a pretty good idea; it is easy enough to do this, too. A good quality gear oil is usually suitable.

Some other hubs (by accident) have holes that allow access; for example SRAM i9 hubs can have lube added via one of the disc mount holes.

With other hubs like N4, N7, N8 hubs, with rotary gear selectors, adding oil regularly is more difficult, but it can be done by removing the LH cone or the RH dustcap. Adding a lube port in an aluminium N7 or N8 hubshell isn't too difficult, but you do need to choose your spot carefully.

If you use oil, monthly top ups are best, just like SA used to recommend. If the hub is fairly well sealed and/or you use a very mobile semi-fluid grease (more mobile than EP-00 even) then the intervals can be even longer between top ups. If you can find a lube with the highest level of corrosion inhibitors (meant for exposed bearings in harsh conditions) then using that will also better protect the hub from water ingress and/or condensation.

cheers

[barrym]

Fascinating read. Do I detect a bias towards SA3s? I'm certainly swinging that way.

Cheers
Barry

[[XAP]Bob]

No need for bias towards a hub which has a century of history, with some examples clocking in that much history on their own...

[interestedcp]

Shimano is kind of schizophrenic about this issue: all their IGH's with 8 gears and less are using grease, but they no longer have instructions on how to re-grease such IGH's, only the oil-bath procedure is documented, effectively turning the hubs into oil-based IGH's.

The reason for this is probably that the re-greasing procedure is very complicated and time consuming. This makes it hard for many LBS' to offer maintenance at a price consumers find acceptable. And preventive maintenance seems to be an extremely hard sell these days, were people prefer to ride stuff into destruction rather than pay for preventive maintenance.

I speculate that there were "good" marketing reasoning behind the removal of the oil port etc. IGH's have been marketed as zero maintenance "sealed units", with a clean and simple design that "hides" everything complicated. So you have people saying that IGH's are simple, even though they are far more complicated than a simple dérailleur, you just don't see that complexity.

Oil-ports and dripping oil were probably orthogonal to that kind of marketing, and grease also last much longer than oil in a IGH.

I would like to add that I don't think the marketing departments are the cause of the oil-port disappearance; I do think it is driven by what the consumers think, and that marketing departments just react to that.

But perhaps it would be a good idea for Shimano, to _also_ make a good quality 5, 7 or 8 speed oil-based IGH with oil-port, and an easy way to re-grease the bearings, made for those people who use their bike a lot in all weather and isn't afraid of using an oil can and doing maintenance. Those people aren't well served by the present Shimano IGH strategy.

[mjr]

Ironically enough you can still add oil to a typical SA three-speed; but it takes a little more effort. You simply select top gear, unscrew the indicator rod, and dribble the oil in there instead.

Do I have to lie the bike on its side to do this (which is rather annoying), or is there an easier way?

[Brucey]

Fascinating read. Do I detect a bias towards SA3s? I'm certainly swinging that way.

Cheers
Barry

Both SRAM and Shimano 3s hubs have some clever design features inside them that make (say) some shifts cleaner and more reliable under load. By design the guts of an SA 3s hub ought to be stronger (in any one gear) than SRAM or Shimano. However if you take a hub out of the box and just use it for five years (no maintenance, no accidents, solo use) I'd expect a Shimano N3 hub to give the least trouble.

Obviously past performance is no absolute guarantee of future success here; until comparatively recently all N3 hubs were made in Japan but now they can come from plants elsewhere, e.g. China, Singapore, or the Philippines, and the quality may vary as a consequence, who knows?

Specific problems with SA hubs in recent years include basic processing failures (which result in parts that fail inside the warranty period; these problems appear to be less frequent as time goes on) and some design issues. Current AW hubs are fitted with a thing called an 'actuator plate' and this is likely to fail in any event eventually and may fail very quickly under certain conditions. The part costs about £1.50 and can be replaced in about 15 minutes if you know what you are doing. I'd suggest that inspection (or just precautionary replacement) of this part once every two of three years is a good idea.

If I am biased against Shimano and SRAM 3s hubs (and therefore more towards SA by default...) it is simply because

a) SRAM and Shimano hubshells can be more easily damaged (as described earlier) and
b) many spare parts have not been readily available in the UK for either type of hub.
c) the way the shift control is implemented at the hub often contains more (delicate/expensive/difficult to source) parts than an SA hub.

So the SA hub isn't leagues ahead in basic durability or anything, but the reality of using and maintaining one over a period of a few years is often a lot better than with other similar 3s hubs.

cheers

[Brucey]

Ironically enough you can still add oil to a typical SA three-speed; but it takes a little more effort. You simply select top gear, unscrew the indicator rod, and dribble the oil in there instead.

Do I have to lie the bike on its side to do this (which is rather annoying), or is there an easier way?

If you use a pump-action oil can, and the nozzle fits reasonably well in the end of the axle (so that oil isn't lost e.g. through the 'windows' in the axle nut) then you can just lean the bike slightly to one side when adding oil. Be careful though; it is easy to add a little too much this way.

I don't necessarily agree with the idea that (sensible) people expect anything on a bicycle to be maintenance-free. It isn't difficult to explain to people that tyres need air and that chains need oil. Putting a few drops of oil into a hub at the same time as the chain is not difficult to understand or to do, even if you pay someone in a bike shop to do it once every few weeks when they pump your tyres up and oil your chain.

cheers

[Des49]

Thank you Brucey for a fascinating post.

[barrym]

Be careful though; it is easy to add a little too much this way.

How much is too much? Or rather how much is just right?

Cheers
Barry

[Brucey]

for oil lubrication of such hubs there is no fixed quantity per se. In something like a partially sealed IGH it is more or less the case that 'more is probably better' up to the point at which it simply leaks out too fast. Since the sealing varies from one IGH to another (even in hubs that are meant to be the same) it is probably a question of 'trial and error' on normal hubs and 'proceed with caution' with SA brake hubs.

BTW if the hub has dried grease in it already, this will soak up oil, but it won't soak it all up at once. It may take a few days for the dry grease to absorb all the oil that it is ever going to. IMHO this is a further shortcoming of the Shimano 'oil dip' procedure; you can reassemble a hub internal that has been dipped and that looks well-oiled, but a few days later there may be no free oil in the hub, because the grease has soaked it all up.

cheers

[St_Ophe]

For me the Nexus/Alfine 8 spd is a paradox. The Shimano marketing fellas quite rightly say that it isn't worth selling many individual spare parts because in the target markets the cost of repair labour is usually higher than replacing the entire internals sold as a complete unit. But the design fellas came up with something that is very repairable.

For instance, the other day when I was tinkering with one of these hubs, I was delighted to find that a large circlip holds the pinion pins in place. Once removed, this circlip allows the pins, planet gears and roller bearings to drop out. So clearly the potential to replace even the smallest of parts is there. But this is strange for something that is supposed to be thrown away. Perhaps it 's cheaper to assemble hubs using this mildly fiddly circlip but other manufacturers seem increasingly to be going for rivetted sub-assemblies.

Perhaps the Shimano designers are looking forward to an age when repair labour becomes cheaper relative to factory assembly. An economist acquaintance of mine is convinced we all get paid far too much and that an adjustment is due (being an economist means that he is almost certainly wrong). Or perhaps Shimano is looking at markets like India, where recreational cycling seems to be taking off. Or perhaps I've totally missed the point. Probably the latter...

So why does SA still offer so many individual spare parts for its older designs? Perhaps it just likes to preserve its heritage. Whatever the reason, I'm very glad that they do.

Brucey - excellent post as usual. What is in this magic semi-liquid grease that you've formulated? Is it a commercial secret? And what are these clever shifting mechanisms that Shimano and SRAM employ in their three spds?

[robc02]

I have only one new - i.e. no oilport - SA hub. Before building it into a wheel I drilled and tapped the shell and fitted an oilport, so now I can maintain it like all my old hubs

I did manage to get oil into the brake of a hub a while ago. I wasn't aware that I was over-oiling, but clearly I was, though the bike was probably left leaning the wrong way (i.e. towards the left) which wouldn't help. I cleaned the linings and drum with white spirit which restored much of the braking performance but its still well below what it should be.

[rjb]

I have only one new - i.e. no oilport - SA hub. Before building it into a wheel I drilled and tapped the shell and fitted an oilport, so now I can maintain it like all my old hubs

I did manage to get oil into the brake of a hub a while ago. I wasn't aware that I was over-oiling, but clearly I was, though the bike was probably left leaning the wrong way (i.e. towards the left) which wouldn't help. I cleaned the linings and drum with white spirit which restored much of the braking performance but its still well below what it should be.

An old trick with drum brakes on my old A35 was to scuff up the brake shoes with a wire brush to remove the glazing. This did improve the braking usually before the MOT.

[Brucey]

I've run several SA brake hubs with 5s and 3s internals. In recent years I've used a rather runny thixotropic semi-fluid grease in them. This stuff is mobile within the hub and will crawl over surfaces etc. It is a pretty good lube, but it gets everywhere if there are any gaps or holes. To deter this from migrating to the brake, (I've used a generous fill of the stuff) I've made an improved LH seal.

Once drum brakes are contaminated with oil, it is almost impossible to get it all out again. I have an idea that you could do it better using a partitioning effect between two solvents, but I've not had the brains to work out which solvents, leave alone the patience to carry it out.

cheers

[robc02]

I concluded that oil lubrication needed to be very sparing in a brake hub - or use some form of grease. I bought some Penrite Semi fluid grease as an experiment. I've yet to try it on the brake/IGH but I've used it in a bottom bracket set on a bike that was seeing off Campag Chorus BB bearings every winter or two.

I've made an improved LH seal

Would you mind giving us more info on this?