Question pertaining to rear wheel offset
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From: Louisville KY
Question pertaining to rear wheel offset
The offset on the rear C5 is 65.
The offset on the rear C6 is 79.
All the threads I've read says the GM rear C6 wheel will bolt right up to the rear C5 with no problem.
14mm seems like a big difference.
It's got to be either too far in or sticking out too far.
Can someone tell me exactly what difference the 14mm will make?
Thanks
The offset on the rear C6 is 79.
All the threads I've read says the GM rear C6 wheel will bolt right up to the rear C5 with no problem.
14mm seems like a big difference.
It's got to be either too far in or sticking out too far.
Can someone tell me exactly what difference the 14mm will make?
Thanks
Race Director
Joined: Oct 2002
Posts: 16,477
Likes: 26
From: Gone
CI 6-7-8-9-10 Veteran
St. Jude Donor '03
The 79mm offset will stick in too far.
The only application of OEM C6 wheels I've seen on a C5, used a spacer to push the wheel out.
(Edited to remove my mis-stated offset calculations).
The only application of OEM C6 wheels I've seen on a C5, used a spacer to push the wheel out.
(Edited to remove my mis-stated offset calculations).
Last edited by Y2Kvert4me; Jan 23, 2005 at 12:16 PM.
Thread Starter
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Joined: Jan 2000
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From: Louisville KY
Originally Posted by Y2Kvert4me
The 79mm offset will stick in too far.
The only application of OEM C6 wheels I've seen on a C5, used a spacer to push the wheel out.
BTW, the stock offsets for the rear wheels are 55mm for the 9.5" C5 and 58mm for the 10.5' Z06 rear wheel.
That 24mm (7/8") difference is partially negated by the 1/2" (12mm) wider wheel, so expect a stock C6 19x10 rear wheel to be about 5/8" further in the fender than a stock C5 rear wheel would.
The only application of OEM C6 wheels I've seen on a C5, used a spacer to push the wheel out.
BTW, the stock offsets for the rear wheels are 55mm for the 9.5" C5 and 58mm for the 10.5' Z06 rear wheel.
That 24mm (7/8") difference is partially negated by the 1/2" (12mm) wider wheel, so expect a stock C6 19x10 rear wheel to be about 5/8" further in the fender than a stock C5 rear wheel would.
Are you sure about the 55mm? I checked my resources and I still come up with 65mm?
I can live with the wheel being a little tucked in. I guess I should be more concerned about the wheel rubbing or hitting something on the inside.
Thanks
Race Director
Joined: Oct 2002
Posts: 16,477
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From: Gone
CI 6-7-8-9-10 Veteran
St. Jude Donor '03
You are correct about the 65mm, sorry for my misinformation.
Not trusting the online source where I had found that 55mm dimension, I just went and dug one of my OE rear wheels out of the garage to physically measure it. Just using a rather imprecise tape measure and straight-edge, based on the actual measured backspace (7 3/4") I calculated the offset at 64mm. (1mm error with a tape measure can be expected).
The wheel is also stamped "18x9.5 J65" which confirms it is indeed 65mm offset.
The conversion to mm is 1" = 25.4mm.
_______________________________
So lets recalculate this all in inches so it's not as confusing:
79mm offset = 3"
65mm offset= 2.55" A difference of (roughly) 1/2"
If the C6 wheel were the same 9.5" width, the additional offset would stick it in 1/2" more.
But, the C6 wheel is 1/2" wider, so to locate the outside edge, subtract half of that width difference (1/4"), and you end up with 1/4" difference.
The OUTSIDE edge of the 19x10 C6 wheel will be approx 1/4" into the fender more.
I stressed outside edge, as this is mainly an appearance thing. For the consideration of any rubbing or inner clearance issues, remember, you are pushing the centerline of the wheel inwards 1/2" (the offset difference), now where we subtracted 1/2 the wiidth difference to locate the outside edge of the wheel, we also need to add that dimension to the inside of the wheel as well (since the wheel is 1/2" wider). So, add that 1/4" additional width to the 1/2" additional offset, and you will need 3/4" additional inner clearance over the stock C5 wheel.
Whether that presents a problem or not, I do not know.
In short, the C5 9.5" wheel is about a 7 3/4" backspace (I measured this).
The C6 19x10" wheel should be an 8.5" backspace....or, as I explained above, 3/4" more.
Hope all that made sense. If not, I can draw it out on paper, it will make more sense then.
Not trusting the online source where I had found that 55mm dimension, I just went and dug one of my OE rear wheels out of the garage to physically measure it. Just using a rather imprecise tape measure and straight-edge, based on the actual measured backspace (7 3/4") I calculated the offset at 64mm. (1mm error with a tape measure can be expected).
The wheel is also stamped "18x9.5 J65" which confirms it is indeed 65mm offset.
The conversion to mm is 1" = 25.4mm.
_______________________________
So lets recalculate this all in inches so it's not as confusing:
79mm offset = 3"
65mm offset= 2.55" A difference of (roughly) 1/2"
If the C6 wheel were the same 9.5" width, the additional offset would stick it in 1/2" more.
But, the C6 wheel is 1/2" wider, so to locate the outside edge, subtract half of that width difference (1/4"), and you end up with 1/4" difference.
The OUTSIDE edge of the 19x10 C6 wheel will be approx 1/4" into the fender more.
I stressed outside edge, as this is mainly an appearance thing. For the consideration of any rubbing or inner clearance issues, remember, you are pushing the centerline of the wheel inwards 1/2" (the offset difference), now where we subtracted 1/2 the wiidth difference to locate the outside edge of the wheel, we also need to add that dimension to the inside of the wheel as well (since the wheel is 1/2" wider). So, add that 1/4" additional width to the 1/2" additional offset, and you will need 3/4" additional inner clearance over the stock C5 wheel.
Whether that presents a problem or not, I do not know.
In short, the C5 9.5" wheel is about a 7 3/4" backspace (I measured this).
The C6 19x10" wheel should be an 8.5" backspace....or, as I explained above, 3/4" more.
Hope all that made sense. If not, I can draw it out on paper, it will make more sense then.
Last edited by Y2Kvert4me; Jan 23, 2005 at 12:18 PM.
Melting Slicks
Joined: Nov 2004
Posts: 2,275
Likes: 6
From: Lake Oswego, Near Portland Oregon
Originally Posted by Y2Kvert4me
You are correct about the 65mm, sorry for my misinformation.
Not trusting the online source where I had found that 55mm dimension, I just went and dug one of my OE rear wheels out of the garage to physically measure it. Just using a rather imprecise tape measure and straight-edge, based on the actual measured backspace (7 3/4") I calculated the offset at 64mm. (1mm error with a tape measure can be expected).
The wheel is also stamped "18x9.5 J65" which confirms it is indeed 65mm offset.
The conversion to mm is 1" = 25.4mm.
_______________________________
So lets recalculate this all in inches so it's not as confusing:
79mm offset = 3"
65mm offset= 2.55" A difference of (roughly) 1/2"
If the C6 wheel were the same 9.5" width, the additional offset would stick it in 1/2" more.
But, the C6 wheel is 1/2" wider, so to locate the outside edge, subtract half of that width difference (1/4"), and you end up with 1/4" difference.
The OUTSIDE edge of the 19x10 C6 wheel will be approx 1/4" into the fender more.
I stressed outside edge, as this is mainly an appearance thing. For the consideration of any rubbing or inner clearance issues, remember, you are pushing the centerline of the wheel inwards 1/2" (the offset difference), now where we subtracted 1/2 the wiidth difference to locate the outside edge of the wheel, we also need to add that dimension to the inside of the wheel as well (since the wheel is 1/2" wider). So, add that 1/4" additional width to the 1/2" additional offset, and you will need 3/4" additional inner clearance over the stock C5 wheel.
Whether that presents a problem or not, I do not know.
In short, the C5 9.5" wheel is about a 7 3/4" backspace (I measured this).
The C6 19x10" wheel should be an 8.5" backspace....or, as I explained above, 3/4" more.
Hope all that made sense. If not, I can draw it out on paper, it will make more sense then.
Not trusting the online source where I had found that 55mm dimension, I just went and dug one of my OE rear wheels out of the garage to physically measure it. Just using a rather imprecise tape measure and straight-edge, based on the actual measured backspace (7 3/4") I calculated the offset at 64mm. (1mm error with a tape measure can be expected).
The wheel is also stamped "18x9.5 J65" which confirms it is indeed 65mm offset.
The conversion to mm is 1" = 25.4mm.
_______________________________
So lets recalculate this all in inches so it's not as confusing:
79mm offset = 3"
65mm offset= 2.55" A difference of (roughly) 1/2"
If the C6 wheel were the same 9.5" width, the additional offset would stick it in 1/2" more.
But, the C6 wheel is 1/2" wider, so to locate the outside edge, subtract half of that width difference (1/4"), and you end up with 1/4" difference.
The OUTSIDE edge of the 19x10 C6 wheel will be approx 1/4" into the fender more.
I stressed outside edge, as this is mainly an appearance thing. For the consideration of any rubbing or inner clearance issues, remember, you are pushing the centerline of the wheel inwards 1/2" (the offset difference), now where we subtracted 1/2 the wiidth difference to locate the outside edge of the wheel, we also need to add that dimension to the inside of the wheel as well (since the wheel is 1/2" wider). So, add that 1/4" additional width to the 1/2" additional offset, and you will need 3/4" additional inner clearance over the stock C5 wheel.
Whether that presents a problem or not, I do not know.
In short, the C5 9.5" wheel is about a 7 3/4" backspace (I measured this).
The C6 19x10" wheel should be an 8.5" backspace....or, as I explained above, 3/4" more.
Hope all that made sense. If not, I can draw it out on paper, it will make more sense then.
Well stated!
