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#21
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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 |
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#22
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Nexus 8 hub durability
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. |
#23
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Nexus 8 hub durability
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 |
#24
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Nexus 8 hub durability
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 |
#25
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Nexus 8 hub durability
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 |
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