I’m hoping to shed some light on the subject and perhaps open up a conversation for anyone interested in nerding out on wheel specs. There is already a helpful diagram floating around the forum on various wheel sizes. The diagram is a good general guide, but there are a few things that need to be considered, like staggered front/back offsets and tire sizes.
Rim Offset
Armed with the latest and greatest in measurement technology, I did some offset maths.
The yardstick is right against the fender through the center of the wheel and it’s leveled to the best of my ability from all angles. I used a ruler to measure the gap between the rim and the yardstick on my 20x7.5 +49.5 OEM wheels (I took both wheels off and verified the size stamps on the inside).
Front wheel needs 33.5mm to reach the edge of the fender. The flush offset is 49.5-33.5=16
If this rim was to be flush with the fender, the rim size would have to be 20x7.5 +16
The rear wheel is the same 20x7.5 +49.5 but it needs 38.5mm to reach the edge of the fender. If this rim was to be flush with the fender the rim size would have to be 20x7.5 +11
Now let’s have a look at the offset calculator.
If we go with a 20x9 wheels, the offsets would need to be 20x9 +35 front and 20x9 +30 rear for a rim-to-fender flush setup.
I found it very interesting that the rear is actually sunken in 5mm more than the front, but it seems consistent with member reviews and pictures. All the postings I have seen are from folks who get the same offset all around, whether that’s +35, +35, or +32, and the usual response is that there is more poke in the front than the rear.
Tire Bulge
Now let’s talk tires because that’s where things get a bit less precise. Flush rims are great, but the tires are likely to bulge out a bit on these cars so we need to take that into consideration. That’s where the poke comes in, and how much poke really depends on the tire.
Every tire manufacturer is a bit different, some tires run narrow and other run wide. People also like to upsize tires to 255/50/20, 265/50/20, and even 275/45/20 which all add some sidewall bulge to the wheel. Adjusting offset for tire bulge is a bit tricky but I gathered some pictures from the forum that provide context.
I have not been able to find a great picture for 255 tires, but here are the ones that I did find:
Front 245/50/20 on 20x9 +38 rims (front rim sunken in 3mm / more tire poke)
Rear 245/50/20 on 20x9 +38 rims (rear rim sunken in 8mm / less tire poke)
Rear: 265/50/20 tires on 20x9 +38 wheels (rim sunken in 8mm / less tire poke)
Front: 265/50/20 tires on 20x9 +38 wheels (rim sunken in 3mm / more tire poke)
Rim Offset
Armed with the latest and greatest in measurement technology, I did some offset maths.
The yardstick is right against the fender through the center of the wheel and it’s leveled to the best of my ability from all angles. I used a ruler to measure the gap between the rim and the yardstick on my 20x7.5 +49.5 OEM wheels (I took both wheels off and verified the size stamps on the inside).
Front wheel needs 33.5mm to reach the edge of the fender. The flush offset is 49.5-33.5=16
If this rim was to be flush with the fender, the rim size would have to be 20x7.5 +16
The rear wheel is the same 20x7.5 +49.5 but it needs 38.5mm to reach the edge of the fender. If this rim was to be flush with the fender the rim size would have to be 20x7.5 +11
Now let’s have a look at the offset calculator.
If we go with a 20x9 wheels, the offsets would need to be 20x9 +35 front and 20x9 +30 rear for a rim-to-fender flush setup.
I found it very interesting that the rear is actually sunken in 5mm more than the front, but it seems consistent with member reviews and pictures. All the postings I have seen are from folks who get the same offset all around, whether that’s +35, +35, or +32, and the usual response is that there is more poke in the front than the rear.
Tire Bulge
Now let’s talk tires because that’s where things get a bit less precise. Flush rims are great, but the tires are likely to bulge out a bit on these cars so we need to take that into consideration. That’s where the poke comes in, and how much poke really depends on the tire.
Every tire manufacturer is a bit different, some tires run narrow and other run wide. People also like to upsize tires to 255/50/20, 265/50/20, and even 275/45/20 which all add some sidewall bulge to the wheel. Adjusting offset for tire bulge is a bit tricky but I gathered some pictures from the forum that provide context.
I have not been able to find a great picture for 255 tires, but here are the ones that I did find:
Front 245/50/20 on 20x9 +38 rims (front rim sunken in 3mm / more tire poke)
Rear 245/50/20 on 20x9 +38 rims (rear rim sunken in 8mm / less tire poke)
Rear: 265/50/20 tires on 20x9 +38 wheels (rim sunken in 8mm / less tire poke)
Front: 265/50/20 tires on 20x9 +38 wheels (rim sunken in 3mm / more tire poke)
