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Any thoughts on aviation grease?

Weefle

Well Known Member
Someday soon I’ll be packing the wheel bearings for the first time on my 10.

Looking at the Shell aviation grease website there are at least 6 greases for aviation. That’s just Shell, I’m sure Mobil and a few others have their selection too. I’m trying to wrap my head around what makes aviation grease so special besides the price. I’ve packed a lot of trailer wheel bearings with good quality grease and never a problem. Greased a lot of heavy equipment as well. In fact when you think about the abuse a small trailer wheel gets vs a short burst of speed on a RV wheel ...I wonder. Also there are a few other grease fittings that are bushings not tapered roller bearings...nose wheel for example. Do I need a special grease for that too?
I’m not suggesting using a $3.00 tube of Walmart grease.

Please school me.
 
I don't think there is any magic to the wheel grease. I know I routinely drive my car in excess of takeoff and landing speeds for most GA aircraft, so whatever works for that car should work fine for a plane in practice.

That being said, if there was ever an issue (wheel fire, brake fire, landing mishap with a seized bearing or axle, etc), would you rather have the report say that Aeroshell 5 was packed in the bearings or an unapproved substance was packed in the bearings. I think that's what it would come down to. Frankly, seems like that's true of a large fraction of the stuff we talk about, right? Cars tend to have a lot more hours on them than planes, handle much rougher conditions (rough roads / off road vs light turbulence), and get inspected a lot less (no one is doing a complete bolt by bolt inspection of my car every year), yet lots of auto part equivalents (electrical connectors, aircraft grade hardware, etc) are frowned upon in the aviation world.
 
I will probably take some flak but there isn't anything special about airplane wheel bearings. The Walmart grease will work fine especially if you use waterproof grease. I use some high dollar lithium based moly grease made by Schaefer?

The important thing is not to mix different types of grease. Find something and stick with it or clean the bearing completely before regreasing with a different type.
 
Just do it

I have been Greased and greased a bunch of stuff in my life.
Packed thousands of wheels in a past life.
But, the one that gets me is the one that doesn't grease something because they can't decide which to use. Or don't think it is the right one.
If it worked on a trailer that gets submerged it water, I am sure it will work on a wheel bearing that only rotates on ground runs.
It ain't that tough.
I bought an RV-6A a few years back and opened up the front axle to do a proper service on it and found corrosion on the axle cause the guy said he didn't have the correct grease. So he didn't do anything.
Any grease is better than none. Now I'm no suggesting you use shortening or the like. But some nice sticky gooey grease is nice to have.
NO need to spend $$$$ on some special what ever on a wheel that turns very little.
My three cent worth Art
 
I have been Greased and greased a bunch of stuff in my life.
Packed thousands of wheels in a past life.
But, the one that gets me is the one that doesn't grease something because they can't decide which to use. Or don't think it is the right one.
If it worked on a trailer that gets submerged it water, I am sure it will work on a wheel bearing that only rotates on ground runs.
It ain't that tough.
I bought an RV-6A a few years back and opened up the front axle to do a proper service on it and found corrosion on the axle cause the guy said he didn't have the correct grease. So he didn't do anything.
Any grease is better than none. Now I'm no suggesting you use shortening or the like. But some nice sticky gooey grease is nice to have.
NO need to spend $$$$ on some special what ever on a wheel that turns very little.
My three cent worth Art

I think you nailed it....lack of maintenance is a huge factor and often overlooked both in aviation and otherwise!
 
I'll add that many of the Aeroshell grease products are still on backorder from ACS. Though Amazon has it for twice the price
 
Just a thought here, take it for what it is worth. $0.02 at best.

It seems like a lot of the specified stuff in the aviation world is derived from what was used when something was first built/done. Then they just wrote down the name of the product in the certification process and it got carved in stone.

It is not that there is nothing else or better, it is what was used for the original cert and never was updated.
 
I like boat trailer wheel bearing grease. Similar rotation rates, loads and it has the ability to withstand occasional wet grass or running through a puddle. Or complete immersion, if it comes to that.

That said, all the wheel bearings on my RV-3B project are sealed. I don't really enjoy greasing wheel bearings.

Dave
 
Mobil

I plan to use Mobil1 wheel bearing grease from aviation aisle of Autozone. Any reason why I should use something else?
 
Just remember, Alaska airlines lost a 727 because a jackscrew had been serviced with an incompatible grease. Likewise Hartzell recently changed their grease recommendation, but cautioned to keep using the old grease until the hub was disassembled and cleaned. Real world, there are lots of choices, but unless you’re sure of compatibility all the old grease must be removed.
 
I like the Mobil synthetic grease, with a slight preference for SHC 220 over the SHC 100. They are both "extreme pressure" (EP) lithium based PAO (synthetic) greases, NLGI #2; the 220 has a slightly thicker consistency and is slightly better at water washout resistance. I use it in all my heavy equipment, and having not thought about it before Oly's post, will be putting it on my wheel bearings too. If you don't need it to say 'aviation,' do a search on "Mobilith SHC 220" (or 100) and you can find it in 14oz tubes at a much better price...same stuff.

==dave==
N102FM
 
I like boat trailer wheel bearing grease. Similar rotation rates, loads and it has the ability to withstand occasional wet grass or running through a puddle. Or complete immersion, if it comes to that.

That said, all the wheel bearings on my RV-3B project are sealed. I don't really enjoy greasing wheel bearings.

Dave

I don’t think water is the issue. Biggest difference aviation has from any other wheel bearing grease is touch down after long flight. Grease maybe very cold from flying at altitude and at touch down wheel goes from zero to 60kts at max load in a millisecond. Not something a boat trail or car experience. That is were your bearing wear will occur Similar to starting your cold engine.
 
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There will be grease on all the bearings and the race at that time, so what would cause would the extra wear? After all, the wheels were rolling until they stopped after take off.

I've landed in tall, wet grass and have observed wet tires and wheels, in my C180. Water resistance is a factor in my opinion. Someone who always operates off of paved runways may not have that need.

Dave
 
Many Hartzell props require Aeroshell 5 or 6 ONLY; no mixing with other lubricants, don't know why. some are discontinued in foreign countries due to back ordering. Hartzell has an alternative #22, but only if the hub is totally cleaned and retrofitted with the new synthetic grease, or is one of the newest hubs.

DAR Gary
 
Marine Wheel Bearing Grease.

Sta-Lube SL3121 Water-Resistant Marine Grease - 14 oz. Tub , Blue
Less than $10 on Amazon or your local Wallmart or Auto Parts store.
Been using on a 1994 RV6 & never have had any corrosion.
It rains a lot in the Pacific West Coast.
 
NGLI #2

As others have said, what's more important is that you actually grease the bearings, and don't forget the nose wheel...

Rather than named aviation brands, I've been using this stuff for many years with great success. Lucas Marine Grease

Any good quality NGLI #2 grease will be fine for this use.
 
Specific differences, but no link to failures due to lube.

There will be grease on all the bearings and the race at that time, so what would cause would the extra wear? After all, the wheels were rolling until they stopped after take off.

I've landed in tall, wet grass and have observed wet tires and wheels, in my C180. Water resistance is a factor in my opinion. Someone who always operates off of paved runways may not have that need.

Dave

Dave, I think the loads are similar, the RPM near the same as smaller trailers, but a cold bearing with near instant load means some inertia on the rollers just as the load is applied. Sliding of any rolling element bearing means higher need for boundary lubrication offered with good EP characteristics. I use SHC 100 Mobil recommended by Parker. I get it in tubes from Grainger and it is cheap that way.

All said, a good lube regularly attended and a sterile application should yield good results. The marine lube may address the odd corrosion failure mode.
 
Just remember, Alaska airlines lost a 727 because a jackscrew had been serviced with an incompatible grease. Likewise Hartzell recently changed their grease recommendation, but cautioned to keep using the old grease until the hub was disassembled and cleaned. Real world, there are lots of choices, but unless you’re sure of compatibility all the old grease must be removed.

Big difference, the jack screw failed due to lack of servicing. Also the requirement for a grease operation at -40 c is a lot different than a wheel bearing on an rv. My jet ski trailer runs hours on end at 80 mph after being doused in saltwater, I think that grease will work on my rv that run maybe 10 miles a month.
 
Correct Facts On "Grease Incompatibility" Accident Theory

Just remember, Alaska airlines lost a 727 because a jackscrew had been serviced with an incompatible grease. Likewise Hartzell recently changed their grease recommendation, but cautioned to keep using the old grease until the hub was disassembled and cleaned. Real world, there are lots of choices, but unless you’re sure of compatibility all the old grease must be removed.

This post is totally wrong in multiple respects.

It was not a 727. It was an MD-83, N963AS, an n-number that happens to appear in my personal logbooks shortly before the accident.

Most importantly, mixing brands of grease or grease incompatibility was absolutely not a factor in the accident, in any respect, as determined by the NTSB after exhaustive analysis.

In fact, after looking at the "mixed grease" issue, the NTSB stated in the accident report at page 141 that the "mixed grease" exhibited lower wear rates on the components that the original "unmixed" grease.

The NTSB did conclude that removing old grease increases the effectiveness of new grease that is subsequently added.

The actual cause of the accident was insufficient lubrication, caused by the airline, manufacturer and FAA approving the extension of lubrication intervals, leading to increased risk of accelerated wear on the component.

See the actual NTSB accident report here, starting at page 178, Conclusion 21 for those not inclined to read the voluminous full report.

https://www.ntsb.gov/investigations/AccidentReports/Reports/AAR0201.pdf

The “mixed grease” theory became a popular urban legend perpetrated mostly in airline crew layover watering holes around the time of the accident. Although totally debunked by actual facts, the theory gained a certain cachet among self styled aviation cognoscenti.

Seeing it here so many years later provides an example of how easy it is for misinformation to be promulgated online by superficially understanding the actual facts.
 
"The actual cause of the accident was insufficient lubrication, caused by the airline, manufacturer and FAA approving the extension of lubrication intervals, leading to increased risk of accelerated wear on the component."

And those intervals 'may' have been extended even further than the "approved" schedule because it was a difficult/messy job that most mechanics didn't enjoy doing, so it may have been accomplished in the break room drinking coffee :eek:
 
It seems I’m guilty of ‘watering hole stories’, and I apologize for any misinformation. Nonetheless, I stand by my conclusion: Hartzell forbids mixing its new (Nyco) grease with its old choice (Aeroshell). Unless you remove all the old grease, you should not mix greases unless you know they are compatible.
 
I don't think there is any magic to the wheel grease. I know I routinely drive my car in excess of takeoff and landing speeds for most GA aircraft, so whatever works for that car should work fine for a plane in practice.

That being said, if there was ever an issue (wheel fire, brake fire, landing mishap with a seized bearing or axle, etc), would you rather have the report say that Aeroshell 5 was packed in the bearings or an unapproved substance was packed in the bearings. I think that's what it would come down to. Frankly, seems like that's true of a large fraction of the stuff we talk about, right? Cars tend to have a lot more hours on them than planes, handle much rougher conditions (rough roads / off road vs light turbulence), and get inspected a lot less (no one is doing a complete bolt by bolt inspection of my car every year), yet lots of auto part equivalents (electrical connectors, aircraft grade hardware, etc) are frowned upon in the aviation world.

To be clear, I’m not advocating the use of aviation grease over appropriate grades of commercial or automotive greases. However please be careful making assumptions about aviation applications as you have above. Specifically, our RV’s have tire diameters that are significantly smaller than most cars, therefore the the wheels see higher rotations speeds than a car that is traveling at similar speeds.

Skylor
RV-8
 
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Aeroshell 5

Sure the Walmart wheel bearing grease will work fine but get a tube of Aeroshell 5 for your next tire change. It's the best.
 
Sure the Walmart wheel bearing grease will work fine but get a tube of Aeroshell 5 for your next tire change. It's the best.

What makes it "best" and what makes it better than something that works "fine"?

I used Aeroshell 22 last month on my RV.

-Marc
 
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What make it "best" and what makes it better than something that works "fine"?

I used Aeroshell 22 last month on my RV.

-Marc
I look at it like this, I certainly wouldn't ground my airplane if all I had in my shop was Walmart boat trailer bearing grease when repacking my RV7 wheel bearings, aeroshell 22 is fine also, its certainly recommended by Aeroshell as an aviation wheel bearing grease.
In the aviation Maintenace industry we mainly use Mobil 28 or aeroshell 5 for wheel bearings and aeroshell 7,17 and 22 are generally used for actuators, and landing gear lube etc. I guess one has a favorite. My Goto is the aero 5. I prefer the thick consistency of it. Just my personal opinion it's worked very well for me for 25 years.
 
Great point that servicing is more important than grease choice.

In our case I like to use AeroShell 5 in all airframe bearings and zerk maintenance fittings. Some wheels (like ABI/Scott tailwheels and main wheel bearings) come new with the great Mobile 1 SHC red wheel grease. I tear down, inspect and re-pack tailwheels every annual inspection which includes washing down bearing and re-packing with AeroShell 5 (along with new seals on the Scott type tailwheels). So that's when the original red SHC is washed away and replaced with AS 5. AeroShell 5 is also one of the most common aircraft greases found at airports and having the commonality is a plus. So if somebody grabs a grease gun to give a shot to a zerk chances are it's AS 5 and should be more tolerant of type mixing. Also, the Mobile 1 SHC only comes in butter lube cans and not in grease gun tubes so if it is desired to use for grease fittings the end user has to pack his own gun tube which is a mess. Great stuff, I just need KISS.

When there is a specific grease called out such as the above case mentioned with respect to propeller hubs then naturally that will be used. But for all other items, including wheel bearings, I like to use AeroShell 5.
 
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My day job is at a helicopter manufacturer, and helicopters have at least 9 million bearings, of every size and type. As a result, we've become grease-ologists. We are always trying new greases, and the results are not always what you may think. In certain applications the new synthetics were great, but in other applications the old dinosaur grease outperformed them.

Bottom line, this is one where I'd be inclined to follow OEM recommendations. While it's true those recommendations may just be based on "that's the way we've always done it", there may be real reasons behind some of these. Absent OEM guidance, I use old school Aeroshell. And to be honest, our RV's use so little grease that even if it the aviation stuff is more expensive you aren't blowing through that much money.
 
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