Hello, I have a question that search doesn't turn anything up for, and for some reason I can't get this right in my head.

I have a set of 17x9.5 C6 Z06 rims that I got off of ebay. they have a 56mm offset.

I cannot find C6 Z06 rims anywhere in a 17x11 size, so I was wanting to widen 2 of these to 11" to put on the rear of my car. I have a fourth gen width rear axle on there.

My question is, with the offset currently being 56mm, when the rim is widened 1.5" (38mm approx) won't that increase the offset 1/2 of the total amount being widened?

In other words, untouched rim 56mm offset, after widening 38mm, the new offset would end up being 56mm+19mm = 75mm total offset??

I believe that would be waaaay too much positive offset, and I'd end up having to stick the rim outside of the fender with a spacer to make it fit without rubbing and I'm NOT going to do that.

I don't want to look like the guys running 15x10 on a 5.5 backspacing with the stupid tire sticking an inch outside of the fender lip.

If that's what will end up happening, I'll sell these and put my zr1 rims back on until someone makes a c6 z06 rim in 17x11 with the right offset.

thanks for your help, I hope I made sense.

 

Every rim that I have seen widened had the material added to the inside of by the wheel. This means that the offset is increased by the full amount that is added. In your case 56mm plus 38mm. This would require like a 3 3/4" wheel adapter. If you can find the right adapter the tire will not stick out anymore than a Zr1 wheel would.

 

I've been awake all night from work so my mind is a little numb, but that just doesn't make sense to me. The offset is the measurement from the mounting surface to the centerline of the wheel. so if you widen something 1.5", the centerline should only move 0.75", right?

Example: a widget 2 inches wide will have a centerline at 1", but if you widen it 1" to 3" wide, the centerline will be 1.5", HALF of the total amount you widened the widget.

Either way, 56mm+38mm or 56mm+19mm, how would that not make it stick out any more if I ended up running a 3 3/4" spacer? especially with my 4th gen width rear end? That just doesn't make sense to me either... because the offset of a zr1 rim is usually 50mm or 36.5mm for the rear on a 17x11" and I don't have to run any spacer with my 4th gen rear (stock 3rd gen is like a 2" & 1.25" spacer depending on which offset you get I believe) and the tire sits flush with the fender

These would be widened on the inside of the rim, just like you said.
Maybe my only option will be to widen on the outside of the rim, making a "dish", which I'm not too positive I'd like on that style of rim. I don't know if it'd belong.

I've never had wheels widened before, so this is kinda new territory for me

thanks for the help

 

ive always been a little confused with offset, i like backspacing better.

What i would do is this. Sit the rim on the rear, so that the outside edge is where you want it in relation to the outside of the fender( keep in mind tire buldge), and determine any spacers that you would need, since you have a 4th gen rear, probably none. then just get under the car and see how much you can widen it to the inside and how much clearancing you need to do.

many people here have 17x11's, usually the tire is sitting flush with the outside of the car, and they have adequate clearance from the lower control arms.
Is this what you are looking for?

 

I forgot that you have a 4th gen rear. Further your explanation of offset is dead on. Your math is right mine is wrong. As for how it would not stick out the adapter simply serves to center the wheel where you want it. If you would not want the wheel to move closer to the outer edge of the wheel well then you can only use up the space between where the tire is currently and inner wheel well.

 

Just wanted to give a quick update. I talked with Skulte this morning and he told me it will work to widen these. I'll just have to end up running a 1.2-1.7" spacer, depending on what looks best.

This is with a 4th gen rear remember, so if anybody is ever thinking about doing this with a 3rd gen rear, you'll have to run something stupid crazy like a 3.5" spacer or something to make it work just like Souseless suggested
(because of the super high 75mm offset created by widening a 56mm offset rim 1.5")

This is possible because even though the wheel has a 56mm offset, it's a 9.5" wide wheel to begin with, so it doesn't stick out as much as a zr1 50mm offset wheel that is 11" wide. So these wheels sit inside the fenderwell as is.

So I guess I need to send these in to weldcraft and get them on order to be widened! Thanks again for all your help, I'll try to post up pictures once I get these back and mounted.

C6 Z06 17x11 rims - yaaay!!!