On my way back home today, I noticed a sound that wasn't there in the morning. As if I were, now and then, wheeling over a small gravel. I inspected the wheels, and noticed a very strange look of one of them. The sound came from the left, and the wheel in the photo is left rear. I am pretty sure this is new. Look sand feels like solidified molten aluminium, but what can it be?!

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1 Answer 1


From here it looks like bubbling paint caused by corrosion under the paint.

If you press one of the bubbles with a finger nail, does it "give"? Does water come out?

  • Or corrosion under plating. Not aluminum melting. Feb 10, 2023 at 17:32
  • Agree, just aluminium corrosion. That will have been growing for a while. Definitely not new.
    – HandyHowie
    Feb 10, 2023 at 21:44
  • Not just nail, but even pressing with a steel key doesn't cause any visible damage to these “bubbles”.
    – texnic
    Feb 11, 2023 at 17:04
  • I thought aluminium alloys do not rust. Wrong?
    – texnic
    Feb 11, 2023 at 17:05
  • 1
    @texnic The only plausible explanation I can think of for aluminum wheels melting between the spokes is if the flux capacitor in the trunk is leaking gamma rays. But you're driving a Volvo, not a DeLorean, so forget that. ;-)
    – MTA
    Feb 11, 2023 at 17:48

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