The Cessna 120-140 Association Forum

Upon inspecting the axles and bolts, there are worrisome signs. Would like to replace the axles with solid ones and go with 5/16 AN5 bolts. I read a service letter where the 1/4 inch holes can be reamed to 5/16 holes and get a field approval. Anyone accomplished this ? Also after a certain serial number and on the straight legs, Cessna did go to 5/16 size bolts, anyone knows if the early 5/16 legs will fit on the earlier models ?

To make things easier, if you have exisiting 1/4" NAS bolts you can try Grove Aircraft and see if they have made a run on the 1/4" axle holes lately. IIRC they were/weren't but you can contact. Much easier than trying to drill holes in your landing gear and dealing with who knows what paperwork. Grove axles have a myriad of 337's floating around already for the 120-140 (although Portland FSDO locally still hasn't confirmed mine from 2019......)

https://www.groveaircraft.com/5016.html

I think the pattern for our birds is on the right #5016 request 1/4" holes early axles

https://www.groveaircraft.com/axletemplate.pdf

John C here on the Forum can get you the proper NAS/MS bolts and correct nuts as he did for me, easy peasy

https://skyportservices.net/cessna.html

This should answer some of your other gear questions=
https://www.cessna120140.com/Forum2018/ ... f=10&t=121

I would put sleeves in the axles before I'd try to drill out the gear legs. I had a friend with a 170 who tried drilling his and he ruined a number of drill bits in the effort.

Don't know how good it is for the gear legs, either.

Is there widespread concern about the hollow axles with 1/4 NAS bolts?

Age related probably. I did a dye-pen on mine and waffled back and forth on what I saw so got some Groves to let me sleep at night.

NAS/MS bolts easy to get from John C. When I dived into owner maintenance 30 years ago I noted some ham handed mechanic put AN-4s in there. Had to beat them out of the gear leg....

Thank you and good idea - I will do dye penetrant tests next time I've got the wheels off. When I did my gear extender removal I found the same hardware scare - every bolt was AN4 with washers covering/protecting the gear leg chamfers.

dcannon wrote: ↑Fri Mar 28, 2025 2:53 pm Is there widespread concern about the hollow axles with 1/4 NAS bolts?

I wouldn't call it "widespread concern", but it is something you want to keep an eye on. Good NAS bolts hold up well, hollow axles do fine, the vast majority of the fleet had them......for ages. That being said, we lose about 1 aircraft every 10 or so years due to either a broken axle or the landing gear legs breaking at the step attach bolt holes. Both (axles and landing gear legs) every 10 or so annuals. I replaced my axles about 8 years ago due to cracks. I check the step bolt holes every annual......just "cuz".

I recently bought a set of Cessna type axles actually with a 1 and 1/4-in axle. So I could use grove wheels and brakes. I know those are only available through CubCrafters. They had Grove make them and a propriety contract and you can only get them from them. Maybe if you call Grove they might have the one and a half inch ones.