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Smoothing inside of 1 1/4 in. Outback trailer hitch?

So I was installing a Thule Ridgeline 4-Bike Hitch Carrier on our 2003 VDC Outback H6 3L 1 1/4 in. hitch receiver (“Draw-Tite” brand that came with the car rated to 300 lbs) and couldn’t slide the Thule Ridgeline Hitch fully into the Subaru Draw-Tite Hitch Receiver (needed to get the hitch another 1-2 in. in to lock the hitch with the hitch pin).

Felt around with my fingers inside and it was feeling a little rough (no big bumps, just not fully smooth surfaces), and I was sure there was a bit of rust inside.

Worked around a rag and got out some dirt debris.

Then gave it a good spray with WD40 and worked around a rag - sure enough it came out very rust colored. Did this several times.

Now I’m letting the inside walls of the hitch soak in a good spray of WD40 for a few hours.

I want to get it to the point where I can not only get the hitch fully into the pin-lock position, but so that I’m confident I can remove it when I want to! The way it is now, if I pounded it in it might be extremely difficult to remove it.


  1. After soaking in the WD40, should I also clean the inside walls of the hitch receiver with a stiff metal brush?

  2. Should I apply any coating to the inside walls of the hitch receiver once clean in order to prevent rust? If I coat it and there’s any rust at all left under the coating, will it continue to rust? Will the rust coat interfere with inserting and removing the bike carrier hitch?

  3. What should I lube the inside of the hitch receiver with? Teflon bike spray, WD40, auto grease? I want to be able to regularly put the hitch on at the beginning of a weekend and remove it Sunday evening.

    The local guys at our local Rack N Road store who are supposed to be experts only murmured WD40 and they seemed like they didn’t have a clue.

I think it might be helpful if you edit your post and change the font color back to black…some folks around here might have some trouble reading it.

Another Rack N Road guy from a different store said that some 1 1/4 in. hitch receivers have a notch stamped, usually in the right inside wall, that has to be chisled out to get the hitch all the way into the receiver. Anyone ever see this or hear of this?

ibid cdaquila’s post

I copied it all to a notepad window to read it.

WD-40 will just continue your rust problem. But this is on a new hitch? I guess they didn’t paint the inside, just the outside.

Clean it out as good as you can, if a wire brush will help, use it. Once it’s cleaned out, use some kind of detergent to get the WD-40 out (I like gasoline, but that’s just me). You could paint it, but it’s probably not necessary. You should use something to lube it, though. Teflon spray sounds good, almost any spray grease should also work.

It’s going to rust again. It’s the nature of the beast. Unprotected metal rusts. Period. Remove the hitch on a regular basis (at least once a month) and check it for rust. If you keep it lubed, it should be OK. If you start to see a bunch of rust, clean it out again.


I wouldn’t coat the inside with anything other than keeping it clean and plugging the opening with a rubber plug. I have taken a metal file and filed all the burrs in the opening. With a little work it should respond. All the wd40 isn’t going do anything if burrs or paint ripples coat the inside. Never push the hitch into the receiver with any more effort than your hands. Do not pound it in ith a hammer… You creat more problems then it’s worth. File away.

Btw, don’t neglect to make sure the entire male end of the rack is smooth as well, all the way to the length required. Both should be worked.

I had this same issue with a used hitch I bought for my minivan last fall. It had a plastic plug in it and had apparently never been used in 12 years or so. The inside was full of rust and scale, and it would not accept the male hitch. I ended up using a hammer and chisel to knock much of the scale off, then followed up with a lot of work with a coarse file and sanding drum attached to a drill. Once the male end would go far enough into the hitch to insert the pin, I applied brake parts lube to both pieces and put it together. Using it to tow also seemed to help break up more scale and allow the parts to fit even easier together. This operation took hours of hard work and was not at all fun.

Clean it out with a file (a nice big heavy one) and for future rust protection, the absolute BEST product is Boeshield T-9 found at marine stores…Trailer hitches are not precision equipment. Wire brushes and files are the proper tools to use. PB-Blaster is a far better spray-lube than WD-40, which is just kerosene…PB also makes a spray grease but it’s messy and not as good as Boeshield…


Don’t worry about it…This is a trailer-hitch…it’s 1/4" steel…It’ll take a couple of decades for the rust to become a problem. This is NOT a problem. Any kind of paint or coating you’ll put on the surface will be scraped away every time you put the hitch in and out of the receiver.