Grease is the word; a complicated word...

General cycling advice ( NOT technical ! )
Canuk
Posts: 1105
Joined: 4 Oct 2016, 11:43pm

Re: Grease is the word; a complicated word...

Postby Canuk » 20 Nov 2018, 5:14am

The utility cyclist wrote:
Canuk wrote:I put copper base gear on everything, even my carbon frames. It's probably overkill but I've yet to experience a problem with anything seizing or getting stuck.

Why would you put copper grease in a carbon frame with a carbon seatpost and/or handlebars, that's actually detrimental and absolutely no need ever to do that. metal on metal, sure, carbon, no way, you could use some carbon paste on the bars if you really want to but that's a different thing altogether. I've been riding dry mounted carbon posts and bars for over a decade on several bikes.


Carbon to carbon bonding is even more likely than aluminium to steel. I got this tip from my lbs who has had the gruesome task of sawing off dozens of carbon posts and delicately reaming out the frame. He says his success rate is only about 20%. The microstructure of carbon fibre is very rough. If you look at it under a microscope you'll see just how rough it really is. Dry carbon into carbon can over time create a fine dirty paste which when it bonds is near impossible to dislodge.

I've been there myself with a Look KG 555. A smear of copper grease would have saved me £1100 on a new frame. In the aerospace industry you'll never find a dry carbon to carbon contact area. For precisely the same reasons. I suppose its like any other mechanical disaster : you never think twice about it till it happens to you!

boris
Posts: 422
Joined: 5 Nov 2010, 1:58pm

Re: Grease is the word; a complicated word...

Postby boris » 26 Nov 2018, 8:13pm

Super essay on grease.

So do I carry on using vaseline or not? The mysterious tube of Lithium grease in my toolbox : does this have unpleasant reactive tendencies as I have always suspected ? I see copper is also being discussed.

I do not understand why metal powder or ions between two other metal surfaces is a good idea.

I had to scrap my 40year old peugeot a few weeks ago so had a good look in the headset , which had never been adjusted or regreased and functioned perfectly. The ball bearings and surfaces were perfect .It was well packed with a transparent brown grease or thick oil which must have magical properties; if only we knew what it was.

Brucey
Posts: 35195
Joined: 4 Jan 2012, 6:25pm

Re: Grease is the word; a complicated word...

Postby Brucey » 26 Nov 2018, 9:14pm

a 40-year old Peugeot could well have had a stronglight headset in it of a type that is basically styled like the old Campag NR headset. There is little to choose in terms of durability between them either. The only black mark against this model of stronglight headset is that it is notoriously difficult to build it up with loose (rather than clipped) ball bearings.

A lot of what happens in a headset or other bearing is simple chemistry; if the conditions (say) tip the pH of the environment very slightly one way, this can favour corrosion of the metal (thus further accelerating the pH change), and in addition degrade the thickener in the grease so that the grease cannot possibly work any more. Depending on the chemistry of the grease one drop of slightly salty water might be enough to set off a chain of events that will result in destruction of the bearing.

I don't understand what you mean by your comment about 'metal particles'. Various EP additives and solid lubricants all work in highly specific fashions and in the main they prevent wear that would otherwise occur e.g. via micro-welding between asperities on the surfaces. None of them might be described as 'metal particles'. Metal particles are used in anti-seize compounds but that is a whole different subject.

Vaseline has its uses for sure but in a rolling element bearing there is always something better you could be using.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

boris
Posts: 422
Joined: 5 Nov 2010, 1:58pm

Re: Grease is the word; a complicated word...

Postby boris » 26 Nov 2018, 9:43pm

Thankyou. I meant in particular copper grease , which looks as though it literally has finely ground copper in it, and is it the same for zinc, aluminium, and molybdenum grease. I suspect that , unlike the truly magical potion added to the peugeot headset, those are sold on a promise that they will somehow reduce reactions that fuse joints and tubes but perhaps they actually increase fusing reactions.

P S yes I have always thought it was a stronglight 1inch headset, but not marked as such. It was of a hardness and overall quality of metal and make that we may never see again. Some old raleigh bikes have similarly tough components.

Brucey
Posts: 35195
Joined: 4 Jan 2012, 6:25pm

Re: Grease is the word; a complicated word...

Postby Brucey » 26 Nov 2018, 10:31pm

you are really talking about anti-seize compounds then. They are not really 'lubricants' per se, not in a bicycle context anyway. They work as anti seize compounds on static parts by inhibiting the reactions that cause seizure, even if it promotes other reactions which you mightn't think are 'harmless' when taken in isolation.

BTW 'Molybdenum' greases usually contain Molybdenum Disulphide; this is a very effective solid lubricant.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

alexnharvey
Posts: 754
Joined: 10 Jan 2014, 8:39am

Re: Grease is the word; a complicated word...

Postby alexnharvey » 1 Dec 2018, 10:16pm

Is Mobil shc460 a good choice for hubs, headsets and possibly BBs? It seems to meet a lot of the requirements. EP, anti corrosion, slow rotation under heavy load. Not too thick overall (nlgi 1.5) and with high viscosity synthetic base.

I think others in the shc range (100, 220, 1500) have been suggested before.

alexnharvey
Posts: 754
Joined: 10 Jan 2014, 8:39am

Re: Grease is the word; a complicated word...

Postby alexnharvey » 9 Dec 2018, 5:49pm

https://ac.els-cdn.com/S0301679X1500461 ... b75777ba06

The LiPAO grease in this study uses a low viscosity synthetic base oil (18cst) yet maintained a good film thickness in their testing. Is there an argument for using such a grease rather than the high viscosity bases we generally discuss here?

Something like skf lgbb2 is the closest I've found at 68cst. Designed for low speed high load applications.

Brucey
Posts: 35195
Joined: 4 Jan 2012, 6:25pm

Re: Grease is the word; a complicated word...

Postby Brucey » 9 Dec 2018, 10:48pm

I would ask 'where is the benefit?' in that at very high speeds there might be a benefit in friction losses but at low speeds they are arguably so small that they are not really worth worrying about in the same way. Possibly there is more lost in the seals (if they are properly wetted with lube) than in the bearings anyway. Also in reality a lot depends on how stable the thickener is, if you are reliant upon that for the low speed film thickness. Plenty of greases start to degrade by the thickener changing first of all. Unfortunately bicycle parts see some pretty horrible conditions and they don't always have perfectly smooth surfaces in the bearings either.

So a grease that works great in a lab test might not work so well in the real world. Ideally you would want to have

- super anti-corrosion additives (clue; the grease is recommended for 'open' bearings and/or gears in mucky conditions)
- grease fluid enough that it keeps seal lips wetted (so the seals can work as intended) but not so fluid that the lube just runs out of the hub (*)
- grease that shears in a particular way so that it doesn't 'ball up' in seals (*)
- EP additives and/or solid lubricants to inhibit wear at the very lowest speeds (they don't even measure at bearing speeds that correspond to climbing in bottom gear)
- a thickener system that isn't destabilised by water, road salt, small amounts of rust, or typical soil chemistries, even under long term exposure.
- a thickener system that works differently under different conditions (**)

(*) the NLGI consistency is rather a blunt tool in relation to what you really need in a bike part. The NLGI test basically measures how easily the grease shears at a certain speed under a drop weight test, i.e. the distance the grease is penetrated is measured. The grease sample is 'freshly worked'; you would get a completely different result if the grease is left for different lengths of time. Nearly all commercial greases 'shear thin' so a small change in viscosity at high speeds affects the test score greatly whereas a large change in the low speed viscosity has a relatively small effect on the test score, even if it profoundly influences the way the grease will work in a bike part.

I've concocted lubes which when sheared, are little more draggy than plain oil is, yet stop flowing under their own weight within fifteen seconds of not being actively worked; to my mind this makes for a pretty good bike hub lube to use in sealed hubs because the lube will keep the seals wetted and coat all the parts inside a hub nicely, but won't allow excessive amounts of leakage to occur when the bike is not in use. In an unsealed hub you would want something thicker than that.

(**) in an unsealed hub especially, how the grease is pushed around by the ball bearings is important. Some greases use additives that tackify the grease and/or make it 'stringy'. In low speed bearings this can help to keep parts coated under conditions that would just push other greases aside.

So the bottom line is that you usually can't just choose a grease meant for another application entirely on the basis of test scores meant for that application; basically you need to do some tests to show that it isn't going to fail (usually in some terribly prosaic fashion) when you start using it on bike parts.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~