Obviously aftermarket wheel. 10.5" backset 25mm with 3/16" spacer=say 20mm works.
Pirelli P-Zero 315/35 106Y (Ferrari Spec). Probably the largest tire we can use without extensive mods inside the wheel well.
Just drove the little torque monster downtown Minneapolis and back early this morning, it was about 50 degrees and it wants to shred those tires at highway speeds! Very sensitive to colder road temps, don't matter how big. Dodge has gifted us with outstanding machines.
A short story on lip dimensions and specs. A 25mm backset on a 10.5" wheel will put the outside lip 3/8" inside of the sheet metal. The OEM 9.5" outside lip with the 18.5 mm backset is 5/8" inside of the sheet metal. Measured the OEM myself with the 305/35 drag radials on it. FYI the tire sides after the bulge of that tire are exactly in line with the sheet metal.
Will the 315/35 R20 tire work on the Hellcat with stock rims and no spacers? I know that I am kind of splitting hairs here, but it looks like the tire height would be closer to what the front tires are.
The problem is backup one step, 315/35 cannot be mounted on the 9.5" wide wheels. Note I bought all new wheels so the back can be 10.5" and get those 315's on the back.
I have not put a 305/35/20 on the Scat Pack rim (I am going to) but on my Camaro SS I put the NT555r 305/35/20 on the 9in wide rear rim and it fit good. It looked really good.