Bare with me kinda long. I ordered 18" A.R.E. iroc replica's only to find out with the 4th gen rear they hang out past the fender. 0mm offset and they dont make a diff. offset for the rear. So I have decided to go with the C6 rims and for 2 days I have tried to search and read and measure and search and read somemore but to no avail. I'm CONFUSED!!! I want 18" front and rear. And I don't know what to get. -56mm or 58mm, will 9.5" work on the front blah blah blah..... HEADACHE!!! Please help me. I found the ones on ebay for $620 and don't understand which ones to order. I know I will need a spacer up front. But do I need a spacer with the rear? Really I have searched and read so much I just can't comprehend all this. Any help would be greatly appreciated!!!

 

bump. Please help!!!

 

This been covered a million times, you do a search yet? I have 17x9.5 +56mm with my 4th gen rear, 2in spacers up front

 

I don't want to get into a dispute, but why spacers and not a more wicked offset?

Edit: I went through about 50 arguments and 10 days of reading about fitment and the correct offsets on my Z31 boards. We dislike spacers over there...ha ha. My head hurt too.

 

Lets look at the facts-

Aftermarket IROC wheels will fit on stock rear end. THey are 0mm offset and 8" wide. They stick out 16mm wider than the factory 16mm positive offset wheel, but fit nicely under the lip still and give that slightly wider stance by 16mm outward or roughly 5/8". 4" + 1/4" lip is 4.25 backspacing on an 8" wheel.

Stock "rear" factory IROC wheel has a 4.9" offset and sits inward 16mm more than the aftermarket ones you bought. Factory "Front" are 0 offset and again are 4.25 backspacing.

you now have a 4th gen rear that is 4" wider overall or 2" wider per side.
1 inch = 25.4mm so you now need a positive offset wheel with at least 51mm more. At most being another 16mm back to stock at 67mm offset.

So there is your range- 51 to 67mm offset. Lower the better bringing the tire lip outward to the fender lip. on the rear. So now you add those figures to the 4.25" original and you now have 6.25 to 6.9 offest on an 8" wheel.

You need to buy an 8" wheel with 6.25 to 6.75 range of back spacing Lower the # the wider the car will look. I would personally buy the 6.25.


Now, add 9.5" wide wheels. We DO NOT want to change the outer lip where the wheel fits under the fender lip so we add the 1.5" extra of the wider wheel to the inner fenderwell. Here's where it gets a little confusing for most. The 8" wheel was 0 offset, SO.... if you had 4.25 backspacing, you have 4.25 front spacing also. The whole wheel is 8.5 wide with the wheel lips.

Gotta go, I will finish later. Sorry

 

I would love to do a nice offset but the C6 rims are only 56 or 58 offsets. I cannot fit what I want (18" irocs) so I have to go to the next option. I.E. C6's. Therefor I need spacers in the front. I have read all of the posts on this but I keep getting confused. I think with 56 or 58mm offset front and rear and LS1 front brakes with 2" spacer it will be ok. I'm just not sure if it's 56 or 58. I really do appreciate all those who took there time to help me and hopefully I can figure this out before monday.

 

WE NEED THIS ON OUR SITE.

Its nice to be in 2 types of car worlds.

Z31 Wheel Fitment Site

NOTE: In each section some people state direct fit, which isn't FLUSH but is direct fit. They fit under the correct fender lip. But if you roll the fenders (technically opening them up to their actual size), that is how you attain TRUE FLUSH. Also factor in lowering a car and camber settings/changes when driving. Also key points in flush fitment.

 

The width of the 9.5" wheel is 10" considering the inner and outer lips. The center line of the wheel at omm offset is 5" backspacing. THis means the front sapcing is 5" also. Lets now move the offest to 4.25 frontspacing like the 8" rim and you are left with a 3/4" positive offset move /or 19mm. Now add the 2" or/ 51mm to the 19mm and you have a total of 70mm offset or/ 2.75 off center towards the positive outer edge. You are now again 2.25 frontspacing just as the 8" wheel was. You backspacing for a 9.5" wheel is 10" overall - 2.25 frontspacing = 7.75 backspacing on the 4th gen rear. You could go as high as 8.25 to give a range but that will set the tire inward looking narrower stance, yet would not rub. Offset range on a 9.5 wheel is 70-82mm giving a 1/2" margin of play under the fender lip.

There are slight descrepencies in factory wheel lip thicknesses that can vary up to a 1/4" in wheel overall width that will vary the final outcome.

The 58 mm offset on the 4th gen rear will sit you out 12mm outer the fenderlip. If I recall, Zepher had that same setup and his wheels looked slightly outward of stock with his 4th gen rear and I believe ZR1 wheels 9.5" wide.

 

I just looked at your cardomain site and can see in this pic it verifies what I just listed. Your wheels are just like Zephers and they sick out slightly too much. Your car would rub if the tire tries to travel up into the rear fenderwell. You are Aporx 12mm outward too much by looks of the bottom picture on this page.

http://www.cardomain.com/ride/2224542

 

Oh yeah, I forgot, rear fenders are rolled, and the front spacer is 2 1/4 inch, not 2 inch. They actually fit better with the 4th gen rear than with the 3rd gen rear with 2 inch spacers. IIRC, the last picture, I just put on the wheels on the passenger side for a test fit.

 

I cant tell for sure but if you had to roll your fenders you achieve what I call TRUE FLUSH fitment. Rolling the fenders is the only way to do so. I HATE battelship fitment.

Nice fitment but you need better pictures kris, showing it. Looks good though.