safe lubricant for my main shock disks

[Derrickearly]

My left main is squeaking a lot. Will someone recommend a safe lubricant to use that will not damage the elastomer please? 
 

Update: All fittings were greased today, and the squeak remains. 

Edited September 10 by Derrickearly
Should have included work already done.

[47U]

6 minutes ago, Derrickearly said:

My left main is squeaking a lot.

Not that I’m doubting your statement… when do you hear this squeaking?

Have you hit all the zerks on the gear to make sure it’s not a dry bushing?

Probably some version of silicone spray would not damage the donuts.  Read the label before application.

Someone with better perspective will be along shortly…

[LANCECASPER]

9 minutes ago, Derrickearly said:

My left main is squeaking a lot. Will someone recommend a safe lubricant to use that will not damage the elastomer please?

I would grease the lubrication points on the landing gear assembly with a grease gun.

[Hank]

Check the wheel bushing for lack of sufficient grease. 

[Derrickearly]

I should have mentioned that the gear was greased today; however, the squeak in the donuts remains. 

[N201MKTurbo]

You need to get something down the center post. My thought would be to use some soap water, but that could rust the metal. 
 

My nose wheel in the past has been soaked in oil for years, and didn’t seem to hurt the disks at all. So, I would use motor oil.

[Derrickearly]

Wrote to tech support at Lord, they have never heard of the shock disks squeaking.  Therefore, they didn't have a lubrication to recommend. I asked what was the elastomer, and he responded with "a natural rubber blend". That rules out using engine oil.

[Derrickearly]

Lord also did not recommend silicon oil.  They did recommend P-80 emulsion or castor oil.

[LANCECASPER]

17 hours ago, Derrickearly said:

Wrote to tech support at Lord, they have never heard of the shock disks squeaking.  Therefore, they didn't have a lubrication to recommend. I asked what was the elastomer, and he responded with "a natural rubber blend". That rules out using engine oil.

It's the gear squeaking not the shock discs. There are some less obvious zerks to grease. Make sure you look in the manual and hit them all.

[Derrickearly]

6 hours ago, LANCECASPER said:

It'a the gear squeaking not the shock discs. There are some less obvious zerks to grease. Make sure you look in the manual and hit them all.

Maybe, but the squeak has a rubber on metal sound to it.  

[Bartman]

I would put the plane safely on jacks and have the maintenance and parts manuals on the wing. Have someone actuate the gear while you watch and listen. Locate every fitting, some are not easily seen. 
 

I don’t have my manual with me but I recall @Hank once documented all of the fitting locations. Mine has one missing and I have to use the needle on that one. Also, you may find the fitting takes grease better in a semi retracted position, and may not take grease at all sitting on the ground. Not trying to tell you what to do, and hope this helps. 

[Hank]

8 hours ago, LANCECASPER said:

It'a the gear squeaking not the shock discs. There are some less obvious zerks to grease. Make sure you look in the manual and hit them all.

Yep. Eight zerk fittings on each main gear, plus the wheel bearing. 

[Fritz1]

yes put plane on jacks and then hit all the grease fittings again, some take grease better when the load is off, automotive stores sell rubber conditioner for door seals, maybe that needs to go down center stem, can't imagine that being corrosive, nose gear donuts see lots of oil, personally I have not seen one that was damaged by motor oil

[Derrickearly]

17 minutes ago, Fritz1 said:

yes put plane on jacks and then hit all the grease fittings again, some take grease better when the load is off, automotive stores sell rubber conditioner for door seals, maybe that needs to go down center stem, can't imagine that being corrosive, nose gear donuts see lots of oil, personally I have not seen one that was damaged by motor oil

Lord is recommending caster oil or P-80. I'll try to figure out how to get that to the "center stem".

[N201MKTurbo]

3 hours ago, Derrickearly said:

Lord is recommending caster oil or P-80. I'll try to figure out how to get that to the "center stem".

Just put some on the top of the center stem under the retention collar. 

[LANCECASPER]

On 9/11/2025 at 1:48 PM, Derrickearly said:

Wrote to tech support at Lord, they have never heard of the shock disks squeaking.  Therefore, they didn't have a lubrication to recommend. I asked what was the elastomer, and he responded with "a natural rubber blend". That rules out using engine oil.

 

On 9/11/2025 at 2:00 PM, Derrickearly said:

Lord also did not recommend silicon oil.  They did recommend P-80 emulsion or castor oil.

 

Hmm, so Lord has never heard of the shock discs themselves squeaking and they manufacture them and have for 60+ years and they didn't have a lubrication to recommend.

The Mooney pilots who have responded on this thread who have at least 100 years experience flying Mooneys have said that it's the landing gear that you're hearing squeak and that the only lubrication needed is just to verify that every zerk has been greased, even the ones that are not noticeable at first glance. (And by the way keep giving it grease til the old grease comes out.)

And you're sure that it's the rubber shocks discs that need lubricating, even though you would probably be the only Mooney owner who has ever done this?

Finally Lord said you could use Castor oil if you wanted to.                 Was that for the Mooney or for you that they recommended the Castor Oil . . .lol?

[PT20J]

MLG trunions are sometimes easier to make take grease if you slightly retract the gear and move wheel up and down while greasing. 

[Bolter]

On 9/11/2025 at 11:48 AM, Derrickearly said:

Wrote to tech support at Lord, they have never heard of the shock disks squeaking.  Therefore, they didn't have a lubrication to recommend. I asked what was the elastomer, and he responded with "a natural rubber blend". That rules out using engine oil.

Like others, I had a steady application of engine oil on the nose gear shocks and tire for years.  No apparent compatability issues  

[N201MKTurbo]

33 minutes ago, Bolter said:

Like others, I had a steady application of engine oil on the nose gear shocks and tire for years.  No apparent compatability issues  

I think it kind of preserves them.

[Kelpro999]

Give your shock disc retainers a little shot of graphite powder below the collar.

[PT20J]

2 hours ago, Kelpro999 said:

Give your shock disc retainers a little shot of graphite powder below the collar.

I wouldn’t do that. Graphite can cause galvanic corrosion of steel and especially aluminum. I believe the Air Force prohibits its use on aircraft. 

[Kelpro999]

On 9/12/2025 at 9:35 PM, PT20J said:

I wouldn’t do that. Graphite can cause galvanic corrosion of steel and especially aluminum. I believe the Air Force prohibits its use on aircraft. 

It’s literally specified in the Mooney service manual.

[PT20J]

3 hours ago, Kelpro999 said:

It’s literally specified in the Mooney service manual.

The only place powdered graphite is listed in the M20J service manual is for the locks.

It is listed as an alternate lubricant for the starter drive and the control tube guide blocks, but in both cases it is mixed with kerosene (starter drive) or grease (guide blocks). Galvanic corrosion will only occur when water is present and the the kerosene or grease would most likely prevent any corrosion. Still, the alternative lubricants listed would be a better choice and don't require mixing.

[47U]

4 hours ago, Kelpro999 said:

It’s literally specified in the Mooney service manual.

For the yoke ball joints in the panel.  I think that’s the only application for the C-model.

When I did my yoke shaft service bulletin, I replaced the phenolic balls and applied graphite powder spray.

[Kelpro999]

The C gets graphite in about four locations but anyways, the idea is to lubricate the top of the shock shaft under the retainment collar as it passes through the gear frame then taxi test. If that doesn’t do it, then move onto loosening the shock, lower bolt and taxi again. Eventually bolt by bolt the problem should be found. If it is in fact, the rubber rubbing on the shock shaft, then some tire talc can eliminate that. Without hearing the squeak ourselves, we could be completely wrong and possibly a wing skin, frame or spar issue.