Nexus 8 hub durability

Steve Weeks wrote:
The first Nexus hub I serviced was a 7-speed, and I used the "official" Nexus grease. It looked like a molybdenum disulfide type of lubricant. The next Nexus was a "regular" 8-speed (as opposed to red-band) and it was lubed with the same grease. When I opened the red-band Nexus-8, I was surprised to see the white lithium-like grease. I have used the black Nexus grease on all these hubs' bearings with no apparent ill effects.


Most likely I'll just add a little gear oil to the hub and watch what happens.

A really clear example of the behavior that's bothering me happened today.
I was accelerating gently in 4th gear, flat ground with a tailwind, for a
couple hundred feet. Something in the hub slipped, then re-connected in
maybe a quarter pedal turn or less. The rest of the 2 mile trip was perfect.
A dozen or so stops and starts altogether, with accompanying shifting. No
other gearbox malfunctions.

On mixing lubricants, I suspect in the early days when everybody made
their own additive package there was some risk of incompatibility. Now
convergent evolution has probably weeded out most if not all of the
oddball concoctions.

Thanks again to all who replied!

bob prohaska

On Sun, 09 May 2021 01:54:03 +0000, bob prohaska scribed:

Steve Weeks wrote:
The first Nexus hub I serviced was a 7-speed, and I used the "official"
Nexus grease. It looked like a molybdenum disulfide type of lubricant.
The next Nexus was a "regular" 8-speed (as opposed to red-band) and it
was lubed with the same grease. When I opened the red-band Nexus-8, I
was surprised to see the white lithium-like grease. I have used the
black Nexus grease on all these hubs' bearings with no apparent ill
effects.


Most likely I'll just add a little gear oil to the hub and watch what
happens.

A really clear example of the behavior that's bothering me happened
today.
I was accelerating gently in 4th gear, flat ground with a tailwind, for
a couple hundred feet. Something in the hub slipped, then re-connected
in maybe a quarter pedal turn or less. The rest of the 2 mile trip was
perfect. A dozen or so stops and starts altogether, with accompanying
shifting. No other gearbox malfunctions.

When I was riding Sturney Archer hubs, this was clear sign of cable
stretch. fixed by taking out a little slack. sometimes just a quarter of
a turn. YMMV.

On Sun, 9 May 2021 01:54:03 -0000 (UTC), bob prohaska
wrote:

Steve Weeks wrote:
The first Nexus hub I serviced was a 7-speed, and I used the "official" Nexus grease. It looked like a molybdenum disulfide type of lubricant. The next Nexus was a "regular" 8-speed (as opposed to red-band) and it was lubed with the same grease. When I opened the red-band Nexus-8, I was surprised to see the white lithium-like grease. I have used the black Nexus grease on all these hubs' bearings with no apparent ill effects.

Most likely I'll just add a little gear oil to the hub and watch what happens.

That should work just fine. What bothered me and prompted my previous
comment was using ATF (automatic transmission fluid). ATF is quite
different from the much thicker than the official gear oil or grease
normally used by the Nexus hub. The idea behind using a thick grease
is to improve adhesion of the grease and the gear teeth (low sling)
and provide a thicker layer of grease between mating teeth.

"Lubrication 101"
https://www.plantengineering.com/articles/lubrication-101/

"High-viscosity oil is used for low-speed or high-ambient-temperature
applications. Low-viscosity oil is used for high-speed or
low-ambient-temperature applications."

"Grease lubrication is generally applicable to low- to moderate-speed
applications that have operating temperatures within the limits of the
grease. There is no universal anti-friction bearing grease. Each
grease has limiting properties and characteristics. "

On a bicycle gearbox, you're dealing with low bearing speeds, low gear
rotational speeds, low temperatures, low loads, and little friction.
In other words, an ideal application for a grease, but not much for an
oil.

So, what happens if you mix oil and grease? Plenty, but what worries
me is the dilution of some additives and the addition of others. If
you look at the recipe for various oils and greases, you'll see a fair
number of additives most of which are in tiny amounts. I don't know
exactly what might happen if the amount of additives change, but I
wouldn't want to find out. For example, the viscosity of the base oil
varies considerably with temperature. Some of the additives help keep
the viscosity within reasonable limits. Mixing and dilution could
ruin that:
"Viscosity of Automatic Transmission Fluid - ATF"
https://wiki.anton-paar.com/en/automatic-transmission-fluid-atf/
The problem is that you won't notice anything wrong until something
gets worn away because the protective lubricating film on the gear and
bearing surfaces is too thin.

To be fair, a bicycle gearbox is such a light load and low RPM that
one could probably use lard (bacon fat) for lubrication. As I recall,
the Nexus hub has no rubber seals, so you won't need to worry if the
lube will harden or depolymerize the seals. Basically, almost
anything that resembles the official lube grease might work. However,
I would not try substituting or adding a thin (less viscous) oil.

Incidentally, I found this interesting warning on a data sheet:
"LIQUID WRENCH® White Lithium Grease"
https://solvewithb.com/tds/GR014.pdf
"DANGER: IMPORTANT: Do not mix greases of different types. Thoroughly
remove old grease before applying."

A really clear example of the behavior that's bothering me happened today.
I was accelerating gently in 4th gear, flat ground with a tailwind, for a
couple hundred feet. Something in the hub slipped, then re-connected in
maybe a quarter pedal turn or less. The rest of the 2 mile trip was perfect.
A dozen or so stops and starts altogether, with accompanying shifting. No
other gearbox malfunctions.

Something didn't slip. Something got stuck and then broke loose. My
guess(tm) is there's something floating around loose inside the hub.

On mixing lubricants, I suspect in the early days when everybody made
their own additive package there was some risk of incompatibility. Now
convergent evolution has probably weeded out most if not all of the
oddball concoctions.

Yep. When engine oils that included a detergent became available,
putting it into anything that previously had been running on a
non-detergent oil, would cause all the accumulated tar to break loose
from the engine walls and obstruct oil flow. That's not going to be a
problem with a bicycle hub. However, the risk today is rendering the
various additives ineffective, which MIGHT not be a problem in a hub.
For example, if whatever additive is used for rust prevention, you
might eventually have a problem.

The MSDS for Shimano hub grease doesn't show much because only toxic
ingredients need to be listed. I think this is it:
https://si.shimano.com/content/safetydatasheet/PremiumGrease_Eng.pdf
It only lists:
2-ETHYLHEXYL-ZINC-DITHIOPHOSPHAT ;
REACH registration No. : 01-2119493635-27-000 ;
EC No. : 224-235-5;
CAS No. : 4259-15-8
https://en.wikipedia.org/wiki/Zinc_dithiophosphate
It's an anti-wear additive and corrosion inhibitor. There's probably
some in whatever oil or grease you decide to add, so you're probably
safe. If that's the only additive in the Shimano grease, then you
don't have to worry (much) about interactions. That leaves the lower
viscosity and thinner lubricating film problems of the ATF + grease
mix, which I consider to be serious.




--
Jeff Liebermann
PO Box 272 http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann AE6KS 831-336-2558

On Sat, 08 May 2021 20:56:48 -0700, Jeff Liebermann
wrote:

The MSDS for Shimano hub grease doesn't show much because only toxic
ingredients need to be listed. I think this is it:
https://si.shimano.com/content/safetydatasheet/PremiumGrease_Eng.pdf
It only lists:
2-ETHYLHEXYL-ZINC-DITHIOPHOSPHAT ;
REACH registration No. : 01-2119493635-27-000 ;
EC No. : 224-235-5;
CAS No. : 4259-15-8
https://en.wikipedia.org/wiki/Zinc_dithiophosphate
It's an anti-wear additive and corrosion inhibitor.

Looks like there's more than one type of Shimano hub grease:
https://ebike.hu/download/3acbec1a38ed6d34/internalhubgrease-clp20191209.pdf
It lists a different collection of ingredients or which 3 are deemed
proprietary. See Pg 3:
Lubricating oils 70 - 90%
Calcium dihydroxide 5% 10%
Bentonite 2.5 - 4.1%
White solid lubricant 2.0 - 3.5%
Quaternary ammonium salt 2.0 - 3.4%
Additive 1.0 - 2.0%
Antioxidant 0.5 - 2.0%
Quartz (SiO2) 0.3%

The lubricating oils are probably mineral oil.
Calcium DiHydroxide is slaked lime. I have no idea why it's there.
Bentonite is a type of clay formed from volcanic ash. Used to improve
heat resistance.
White solid lubricant is probably a white lithium stearate or black
molybdenum disulfide.
Quaternary ammonium salt is basically water softener salt.
Additive? No clue.
Antioxidant? No clue.
Quartz is an abrasive used to help break up oxides and provide some
resistance to local heating.

Kinda looks like the Shimano Hub grease is not as simple as I
originally thought. Offhand, I would guess(tm) that most of the above
additives are to extend the maintenance interval and life of the hub.
I'm not certain, but diluting these with ATF sounds like it might be a
problem later in the hubs life.

https://www.mcmaster.com/lubricants/additive~quartz/
Click on "About Grease"

--
Jeff Liebermann
PO Box 272 http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann AE6KS 831-336-2558

On 5/8/2021 10:04 PM, News 2021 wrote:
On Sun, 09 May 2021 01:54:03 +0000, bob prohaska scribed:

Steve Weeks wrote:
The first Nexus hub I serviced was a 7-speed, and I used the "official"
Nexus grease. It looked like a molybdenum disulfide type of lubricant.
The next Nexus was a "regular" 8-speed (as opposed to red-band) and it
was lubed with the same grease. When I opened the red-band Nexus-8, I
was surprised to see the white lithium-like grease. I have used the
black Nexus grease on all these hubs' bearings with no apparent ill
effects.


Most likely I'll just add a little gear oil to the hub and watch what
happens.

A really clear example of the behavior that's bothering me happened
today.
I was accelerating gently in 4th gear, flat ground with a tailwind, for
a couple hundred feet. Something in the hub slipped, then re-connected
in maybe a quarter pedal turn or less. The rest of the 2 mile trip was
perfect. A dozen or so stops and starts altogether, with accompanying
shifting. No other gearbox malfunctions.

When I was riding Sturney Archer hubs, this was clear sign of cable
stretch. fixed by taking out a little slack. sometimes just a quarter of
a turn. YMMV.


Good point.
On an SA gearbox (or Shimano or Sachs) a kinked gear wire
wrecks shift position accuracy. Some of the shifter pull
merely straightens the kink without moving the clutch. An
'adjusted' gearbox with a kinked wire will be different in
low gears than in high.

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971