Mooney landing gear shock disk

[dfurst]

I have had my M20K model for 4 years and I had to replace the landing gear shock disks soon after I purchased it.  I now have to replace them again.  This brings up two questions.

 

1) It seems there is only one option? Lord J11968-14 Mooney Landing Gear Shock Disk.  I am surprised none of the aftermarket Mooney people have come up with a better option.

 

2) how long should they last?  I know a 231 is a "heavier" Mooney so they won't last as long as on a C model.  Is 3-4 years normal?  I guess hours is a more accurate measure.

[DonMuncy]

That seems awfully short life to me. My 231 has (to my knowledge) only had two sets in 31 years. I would carefully question the necessity of changing them now. As I understand it, when the plane is put on jacks and allowed to sit with no pressure on the discs for several hours, they are checked to see if they can be rotated by hand. If there is space between them, or they are loose, they need replacement. 

[Bob_Belville]

The disks on my E are still fine as of annual this month. Last replaced 11 years and 450 hours ago. I could not find any earlier entry so I don't know about the previous set. More than 20 years.

 

As I understand it, the hardest thing on the disks in sitting for weeks on end. Since I have jacks, my A&P suggested that if I know I'm not going to fly for several weeks I ought to jack it up and let the disks relax during the idle time. I think he was at least half serious.

[Marauder]

Mine were replaced in the Spring at my annual. My decision to replace them was because they periodically wouldn't expand enough to let the mechanical squat switch get activated. They were replaced last in 1989 (24 years in service).

 

I will look up the part numbers used.

[Earl]

That sounds way too soon.  I replaced mine that were OEM so they lasted over 20 years.  No issues after 4 years with the new ones.  Same shop that did the original replacement?  If not, I would get another look at them to be sure.  Just sounds way too early unless you have done a lot of flying and landings.

[BigTex]

I've heard the original discs were only good for around 5 years. The Lord discs should be good for at least 12 years. The problem we have is determining when to replace them because we get accustomed to the ride due to the length of time they last. Unless you ride in a plane with new discs you may never know it's time to replace them. When I purchased my plane, the prior owner said the discs were in great shape. But during the pre-buy, Don Maxwell said that it road like a tank and he was exhausted just taxiing out. The owner was shocked that it the condition was to the point Don considered then an airworthy item. This find paid for the pre-buy three times over. Reason 56,345 to always have a pre-buy.

[OR75]

what is the reason given for the need to change ?

[Danb]

We are conditioned to keep our tanks full due to the sealant and not wanting a a weeping wing..it is suggested to keep some weight off the gear by not keeping the tanks full....damned if u do damned if we don't...if you had a long body Mooney 3-4 yrs is avg. life. Yikes

[OR75]

and in CA , not a good idea to leave and aircraft on jacks

[Bob_Belville]

and in CA , not a good idea to leave and aircraft on jacks

Earthquake, I guess? I don't think I would actually do it anyway, even in my locked private T Hanger. Murphy rules the world.

[1964-M20E]

Earthquake, I guess? I don't think I would actually do it anyway, even in my locked private T Hanger. Murphy rules the world.

Jacks would add one more thing to do before and after a flight but I guess if you just took some of the weight off the discs not hoist it into the air it might not be too bad.  You could always get an air bag about 7’ square by 2 ‘ high or a few twin sized air mattresses with the pumps set on a timer and put it under the plane and use that to gently lift the plane.

[rgpilot]

I replaced my dics after 20 years. I didn't find any real problems, they finally failed the Mooney spec.measurement.

[stevesm20b]

I think they should last at least 10 years.

[N9201A]

Had my J's disks replaced in 1998 and again in 2012.

 

In my case, the gear wobbled enough when retracting to permit the door to nick the wing fairing behind the mainwheel wells.  This was confirmed when we swung the gear and could move the maingear legs because of insufficient tension in the disks.

[flyboy0681]

I think they should last at least 10 years.

 

Ten years is what I've been told and at 11 years the ones on my J were out of tolerance and were replaced last year at annual. The date of manufacture is stamped on each disk for easy determination of their age, although they may have sat on the shelf for a while. 

[jcolgan]

About to replace my discs.  Currently have (3) Lord J11968-14 on the nose and (4) Lord J11968-5 on each main. I can’t find any information about the J11968-5 donuts, doesn’t appear they are made anymore.  I also need to buy or rent the gear tension rigging tools.  Does anyone know where I might locate these tools? Anyone ever seen or heard of the Lord J11968-5 donuts before?  
original parts manual shows 3CRE714 discs, SBM20-139 installs Lord 530021. I believe J11968-14 is equivalent to 530021, but am not positive.

[Shadrach]

31 minutes ago, jcolgan said:

About to replace my discs.  Currently have (3) Lord J11968-14 on the nose and (4) Lord J11968-5 on each main. I can’t find any information about the J11968-5 donuts, doesn’t appear they are made anymore.  I also need to buy or rent the gear tension rigging tools.  Does anyone know where I might locate these tools? Anyone ever seen or heard of the Lord J11968-5 donuts before?  
original parts manual shows 3CRE714 discs, SBM20-139 installs Lord 530021. I believe J11968-14 is equivalent to 530021, but am not positive.

I believe Mooney switched from using J11968-5s to 3 J11968-14s in 1967.  My 67F came with -14s from the factory. I’m pretty sure your revised IPC calls for -14s all around. I’d be curious to learn the date code on your main gear discs.

[jcolgan]

[Shadrach]

1 hour ago, jcolgan said:

Interesting. Clearly they were made in 1969. Maybe my old ones were -5s. I’ll look this week. 

[LANCECASPER]

1 hour ago, jcolgan said:

It's definitely time, those were made two months after man landed on the moon.

They would buy those in Canada to use for hockey pucks.

[Schllc]

Wow, got your money outa those!

[Hank]

12 hours ago, jcolgan said:

That's when mine were made. I replaced them in Dec. '12. Taxis better, first few landings were much smoother; now I'm either used to it, or my landings just aren't quite as good.

[Shadrach]

On 1/30/2024 at 6:51 AM, Hank said:

That's when mine were made. I replaced them in Dec. '12. Taxis better, first few landings were much smoother; now I'm either used to it, or my landings just aren't quite as good.

Operationally, I felt zero difference between old and new. However, my old disks tested fine until I jacked up the plane on a winter day (high 20s). Lots of slop in the gear for about ten minutes then they were tight again. Mine were still soft and only slightly compressed when replaced.

I “think” the new ones expand better in cold weather, but I’ve not had the plane on jacks in sub freezing temps to verify

[jcolgan]

I got all my shock discs changed and then taxi tested.  The new disc on the nose wheel moved the contact point with the ground far enough forward that it is now unstable at high speeds. Not stable in a straight path at all. I have purchased the spacer from Lasar and it is in route to be installed. Anybody have any experience with this?  From the service bulletin if the center of the nose wheel shaft is more than .06 inch forward of the plumb line you need to shim. Looks to me like mine is about 3/8 of an inch forward of the plumb line with the new discs in place. Wondering if that shim is going to be enough to get it down to less than .06 inch.

Edited March 21 by jcolgan

[Shadrach]

36 minutes ago, jcolgan said:

I got all my shock discs changed and then taxi tested.  The new disc on the nose wheel moved the contact point with the ground far enough forward that it is now unstable at high speeds. Not stable in a straight path at all. I have purchased the spacer from Lasar and it is in route to be installed. Anybody have any experience with this?  From the service bulletin if the center of the nose wheel shaft is more than .06 inch forward of the plumb line you need to shim. Looks to me like mine is about 3/8 of an inch forward of the plumb line with the new discs in place. Wondering if that shim is going to be enough to get it down to less than .06 inch.

Do you still have a compression tool on hand?  Whoever does the installation will need to compress the shock discs.  I would also look closely at the collar.  I am not sure that the bolt hole is centered on the collar. In other words, the dimensions may differ meaning that the geometry of the gear might be affected by on which side of the collar if facing up.  Seems odd that installing new, uncompressed discs on would require a spacer when old discs did not.  There was not a lot of difference in thickness between my old and new discs but there was some. The new disks were definitely thicker if only marginally.