Superduty
Adventurer
The radius to the top arc is right at 20". This would be measured from the horizontal center of the tire mount. So if you made a 40" diameter circle, and cut it in half, and taped the flat edge along the horizontal centerline of your spare, it should give you a decent representation. The "wing" on the passenger side is down about 3" from the top, the passenger side "wing" is about 7" wide, and goes straight down the side. The wing for the fuel cap is down about 2-1/2" from the top, and is about 3" wide.
Measuring from the vertical center to the sides is about 18" to each side.
Measuring from the vertical centerline to the bottom is about 9-1/2", and it slopes up towards the passenger side.
And it's about 5" thick, to where the spare tire would sit.
Hope this helps.
You have spare tire, trekker, extra Jerry can holder and cargo rack ALL on the JKs back door?
Can it handle that kind of weight?