I did a look at the parts catalog but not certain which build you have as there are two for that year, so do some checking to verify but it appears there is a release on two vertical metal supports which will let the rack swing down. I've marked what I " think" is the release in yellow and the swivel in blue on these snips.
Maybe remove two lug nuts to swing the rack down to remove the tire?
Full info and parts are here:
https://catalog3d.winnebagoind.com/menu/Parts.htm
First pic is looking down from slightly above and behind, kind of "Superman" style and then a snip from your picture?
Click this picture to get a better look?
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Richard
Why no RV year, make and floorplan on MY signature as we suggest for others?
I currently DO NOT have one!