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Back spacing/offset conversion question
I was wondering if anyone knows if 20x9 wheels with a 6.5" backspacing will fit with out fender modifications on our cars. Backspacing is a new concept to me, but it looks like the proper way to convert backspacing into offset is to subtract the centerline from the backspacing measurement and multiplying by 25.4.
I guess the main part of the equation I am missing is the centerline. Does anyone know what the centerline is on a 20x9 HRE wheel? Thanks:thumbup: |
It's 20x9 +38 for the short answer. This will fit the GS well.
I did that in my head... (aren't I great?) :D The thing most people miss with these calculations is the rim flange thickness. A 20x9 wheel is the bead-to-bead measurement... you have to add in the thickness of the beads to get the true centerline. The HREs are 1/2" per side. Breakdown: 20x9 + 1/2 + 1/2 = 20x10 (overall width) 20x10 / 2 = 5" (centerline) backspacing 6.5" - centerline 5" = 1.5" (this is the "offset" number in inches) 1.5 X 25.4 = 38MM final offset number |
Damn.....
Originally Posted by SoCalSC4
(Post 2802037)
It's 20x9 +38 for the short answer. This will fit the GS well.
I did that in my head... (aren't I great?) :D The thing most people miss with these calculations is the rim flange thickness. A 20x9 wheel is the bead-to-bead measurement... you have to add in the thickness of the beads to get the true centerline. The HREs are 1/2" per side. Breakdown: 20x9 + 1/2 + 1/2 = 20x10 (overall width) 20x10 / 2 = 5" (centerline) backspacing 6.5" - centerline 5" = 1.5" (this is the "offset" number in inches) 1.5 X 25.4 = 38MM final offset number Bob, You are the man!;) -Joe |
Originally Posted by SoCalSC4
(Post 2802037)
It's 20x9 +38 for the short answer. This will fit the GS well.
I did that in my head... (aren't I great?) :D The thing most people miss with these calculations is the rim flange thickness. A 20x9 wheel is the bead-to-bead measurement... you have to add in the thickness of the beads to get the true centerline. The HREs are 1/2" per side. Breakdown: 20x9 + 1/2 + 1/2 = 20x10 (overall width) 20x10 / 2 = 5" (centerline) backspacing 6.5" - centerline 5" = 1.5" (this is the "offset" number in inches) 1.5 X 25.4 = 38MM final offset number :D:D:D:D:D You are the man Bob:thumbup: |
Originally Posted by SoCalSC4
(Post 2802037)
It's 20x9 +38 for the short answer. This will fit the GS well.
I did that in my head... (aren't I great?) :D The thing most people miss with these calculations is the rim flange thickness. A 20x9 wheel is the bead-to-bead measurement... you have to add in the thickness of the beads to get the true centerline. The HREs are 1/2" per side. Breakdown: 20x9 + 1/2 + 1/2 = 20x10 (overall width) 20x10 / 2 = 5" (centerline) backspacing 6.5" - centerline 5" = 1.5" (this is the "offset" number in inches) 1.5 X 25.4 = 38MM final offset number Thank you sir! As I was writing the thread, you specifically came to mind. I estimated 1/2" per side, but really wanted to make sure. Thanks again, you the man :thumbup: |
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