What is this stuff?

[Young&Fast]

I pulled the rim strip on my front rim today and got a weird surprise. It looks like the rim flaked apart. Is this common? Any fixes, does it compromise the rim or can I still run it, Anything is welcomed:)

[cosmo]

since the rim is aluminum it's oxidizing,flaking away. from moisture getting in there. If it's real bad,start thinking about a new rim,spokes (Excel!). If it's minimal,wire brush it clean,wipe the rim down with contact cleaner (brake parts cleaner) and duct tape the rim. Throw away the the rim strip (rubber band).

[boothe]

It's a little hard to tell from your photos what's happening. From the pic's it looks like maybe someone may have used duct tape as a rim strip and it just decomposed. The first photo looks like it's gummed up adhesive. As was suggested...clean it up and see if you have an degrading of the rim. If so...better think of a new rim, but i've never seen one degrad that bad. Good luck......

[Wayne_Nosala]

Wild guess.

Since it appears most of the damage is near the valve stem,

I would suspect someone along the line used some kind of
"quick fix" sealer that did not agree with aluminum wheels.

Wayne

[FABRICATOR]

That looks like some pretty deep corrosion around the valve stem hole. If it is and you ride mild and don't jump, it may hold for a while. I you ride aggressively at all, I'd replace it ASAP.