For fitment confirmation I thought I'd calculate the total amount of working room in the front. When doing so, something surprised me. Since tires are changing, I realized I need to be measuring tire section width and not wheel width. All measurements not stated are in mm.
Toyo A36 225/55/19
Section width on a 7" wheel: 9 inches or 228.6mm
Outside distance from tire to flush: 20
Inside clearance: ~35
Total: 283.6
Continental DWS06 Plus 245/45/20
Section width on a 9" wheel: 10 inches or 254mm
Remaining clearance: 283.6-254 = 29.6
Wait, why do I have over an inch of clearance left? I increased the wheel width by 2 inches and I only have 2.2 inches in total.
...it's because the section width of the stock tire is quite wide, at 2 inches wider than the stock wheel. The width of the new tire will only be 1 inch wider than the wheel. There's the extra inch! And it's probably the cause of the squishy stock feel.
It doesn't look like it, but I can't deny the numbers. I went out and measured the Toyo and sure enough, it's 9" wide at the sidewall. This confirms there is
plenty of room left for a 245 tire on a 9" wheel. Now to find the new offset.
If current flush fitment (front) is section width 228.6+20mm spacer
Then
New flush fitment would be section width 254-228.6 = 25.4/2 = 12.7 each side +7.3 = 20
So the offset needs to be quite different than I thought, at 45-7=38. This isn't making sense to me because according to
https://www.1010tires.com/Tools/Wheel-Offset-Calculator# that would put my wheels out by 32mm.
We know this kind of offset causes serious poke so I must be doing something wrong.
Here's a 20x9 +35. Thank you,
@ziggi.
My measurement from front wheel to flush with fender is 24mm. Logic would dictate that the 9" wheel would already be flush at 46/47 offset (from 7 to 9 inch wheels is a 1 inch increase to each side = 25.4mm out). But it goes further, because I'm looking for flush tires, not flush wheels.
I think I'm losing it...