Maybe an image of another newer growth on the Sherman will help determine the cause/reason;

Anyhow the wheels are lovely, I think they are a closer size (by eye) to real though calculation says different. I have wanted these done for a while but the brain didn't click. YHR showed it could be done oh his Sherms so I decided to pester Nick .
Had to find a donor wheel from the 21st C Sherman, annoyingly I sold one a few months back so asked the buyer (panzer3 on rctw) to send me a spare from it and he kindly obliged.

Cheers