The Cessna 120-140 Association Forum

I plan to put 8.50s or 26" ABW on the C120 soon. From what I understand running wheel extenders with larger tires isn't the best idea due to added stress to the gear. I generally don't like how they make the airplane handle when up on the mains. Has anyone done this before? I know I'll need to get a new W&B when this is complete, anything else I should consider? Is this considered a minor and can simply have an A&P do it?

Another thing I know I'll need is to modify my brake lines. Right now they are a solid line that goes directly into the caliper. I'm thinking I can cut the line at the last elbow before the caliper then bend it down to the new position. My other idea was to cut it at the bottom of the gear and use a flex line into the caliper. Is there a preferred method? Photo attached.

As always, thanks for the help.

I am assuming you have the un-swept early style gear, hence the extenders.

If you have the 5/16" holes then you are golden being able to use AN5 hardware. If you have the 1/4" holes then you will have fun finding the proper NAS144 type bolts. Definitely don't use AN4 bolts on the 1/4" holes, they have to be NAS144's (MS20004-xx)

Below is one idea for brake lines, my IA used to work on Dash8's and these came off somewhere on one of those....

Thanks for the photo David. That's basically what I had in mind for the brake line. Seems like that would be the most straight forward way to do it.

You CANNOT use solid lines on Cleveland brakes. (legally). The calipers are floating and need to be free to float.

Removing the extenders is a minor modification. An A&P can do it with a log book entry. As stated, be sure to use MS20004 bolts if you have 1/4" holes. MS20004-28 bolts work in about 99% of situations. Hard to tell from the photo what is in there now, but the extenders were all made with 1/4" holes.

I noticed there are washers under the bolt heads in one of the photos. This is not correct and could be a real issue. there isa fillet under the head of the bolt for strength and a standard washer will create a stress point at the fillet, in addition to being too soft to withstand the maximum tension the bolt can handle, which means the bolts could loosen up (and snap.) The gear legs are machined with a chamfer to accept the fillet on the bolt, so no washer is needed. There is a washer made for that purpose. It is MS20002C4 and has a relief for the fillet and higher tensile strength, but they are not called for in this application. If washers are required to accommodate the bolt length they should be MS20002-4. Also, the nuts called for were industrial grade and are no longer available. An appropriate nut is NAS1804-4, to match the strength of the bolt. Standard MS21044 nuts will fail way below the rated strength of the bolts. It has 12 points instead of 6 flats.

Thanks John,

Does that mean you can't use solid lines at all? Or is the short bit of flex line as pictured above ok?

I do wish someone like you was local and could give this plane a solid once over. Seems like the more I look into the more issues I find.

Yes, all you need is a short piece of flexible line to allow the caliper to move. 12 inches or so will do fine, as long as it's got enough slack that the brake doesn't bind up. Cleveland supplies a drawing. I'll see if I can dig up a copy.

I just realized you have the O-290. You better check the STC requirements. Those extenders may be required... Is your CG at the forward limit?

IIRC the STC just requires maintaining the CG within a range, but I will double check. The previous owner who put the O-290-D in did put 3lbs in the tail to help with the CG. The W&B shows that the CG never falls out of range with the lightest takeoff load or at max gross.

Anyone have any suggestions on where to find SS brake line as pictured in that second photo? Or better yet what is supposed to be used for the Cleveland brakes? I looked through my aircraft documentation and didn't see anything specific. I'm definitely missing some documentation here and there. Aircraft Spruce didn't have anything that looked like SS line.

Thanks,

The externally braided lines are not allowed. They can be near failure and not be detected early because the braid covers the rubber.