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Ive been toying with the idea of changing rims. It doesnt seem like a lot of the rim sites have the right offset for my car and I think they mix with the later c4's. Ive done some searching online and the only definitive numbers I can find are from the stocks rims being 8.5 inch width with a 32mm offset and 9.5 inch width with a 38mm offset. So by my logic that changes 6mm a inch of rim width. So a 10 inch wide wheel would be 41mm and a 11 would be 47mm. and a 8 inch would be 29mm Is that correct? Also for those that have done this, what is the widest rim and tire size that fits without rubbing on the front and the rear? Ive always been a fan of keeping all four corners the same, but may go wider on the back. Thanks for your help
I changed the rims on my 86 about 2 years ago. I went with 9.5x18" 40 offset rims on all 4 corners and 255x40zr18 tires so it's a 4 square setup. They fit just like the originals did and there's a whole lot more options on 18" tires than 16". I wanted something that fit just like the originals did and these do. I've had no issues with them since putting them on. One advantage of this setup is if you ever have a problem on the road, you have a lot more options of getting a replacement than if you stayed with the smaller sizes.
Here's where I got he rims I put on my car: http://www.streetdreams.org/oe-replicas-wheels/
I have no connection to them, just passing along where I eventually found rims. It took a long time to find anyone that listed the size and actually had them.
I got what I think was a good price, style and quality, they were very knowledgeable and look great today.
So by my logic that changes 6mm a inch of rim width. So a 10 inch wide wheel would be 41mm and a 11 would be 47mm. and a 8 inch would be 29mm Is that correct?
Unfortunately it doesn't work that way. Basically, an early C4 can tolerate up to about 7.26" of backspacing, but narrower tires than 11" will look a little "set in" with that much backspacing. An 11" wheel on your car will want no more than 32mm offset. Any more and you risk rubbing something on the inside. But if you get wheels with more offset than that (which are more common these days), you can use spacers to move them out. Spacers effectively subtract from offset and backspacing. So for example, if you found later 17x11 wheels with 50mm (which are correct for a later C4), you would use 18mm (or 3/4") spacers to get an effective offset of 32mm.
Also for those that have done this, what is the widest rim and tire size that fits without rubbing on the front and the rear? Ive always been a fan of keeping all four corners the same, but may go wider on the back. Thanks for your help
Generally, the widest tire that will fit within the fenders of any C4 is an 11" wheel with 315-width tire. You can fit those at all four corners with the proper offset (32mm).
Last edited by MatthewMiller; Jul 7, 2019 at 10:29 AM.
ok, that confuses me even more lol. I thought that offset was measured from the center of the wheel to the mounting plate that goes flat against the rotor. So wouldn't as the rim gets wider that number would have to get bigger because the center of the wheel would be moving back as the fender line is static. I would think on a 11 inch rim a 32mm offset would make the rims stick out from the fender by 1 1/4 inches, because thats the same offset as the factory 8 1/2 inch rims ( basically adding a 1 1/4 on each side of the rim if the center stayed static)
ok, that confuses me even more lol. I thought that offset was measured from the center of the wheel to the mounting plate that goes flat against the rotor. So wouldn't as the rim gets wider that number would have to get bigger because the center of the wheel would be moving back as the fender line is static. I would think on a 11 inch rim a 32mm offset would make the rims stick out from the fender by 1 1/4 inches, because thats the same offset as the factory 8 1/2 inch rims ( basically adding a 1 1/4 on each side of the rim if the center stayed static)
The key is that the stock 8.5 et32 has 1.25" of room on the inside and outside before it rubs on the inside or sticks out on the outside. That's a fairly narrow wheel/tire combo in a wheel wheel that can accommodate up to 11". Chevy centered the wheel in the well, though. It has 6.01" backspacing on the inside, so adding 1.25" there puts us right at the limit of backspacing. And on the outside, it the stock whee/tire is about 1.25" inside the fender edge. So keep 32mm offset and adding 1.25" is just right.
oh I don't know.....sunday morn, bored, thought this was a forum.....from now on we'll just listen to you
Way to miss the point. You and anyone else is of course welcome to post here. Just stay on topic. I mean, I could post about sea bass recipes and the Mississippi River flood stage, but that isn't very useful for the OP or anyone else who tuned in here to get info on early C4 wheel offset and width. Or worse yet, you may be confusing the OP by implying that wheel diameter has something to do with the widths and offsets that will work on a C4.
Way to miss the point. You and anyone else is of course welcome to post here. Just stay on topic. I mean, I could post about sea bass recipes and the Mississippi River flood stage, but that isn't very useful for the OP or anyone else who tuned in here to get info on early C4 wheel offset and width. Or worse yet, you may be confusing the OP by implying that wheel diameter has something to do with the widths and offsets that will work on a C4.
Let's see some of your comments regarding 'Mississippi River Flood Stage' and 'Sea Bass Recipes' - You should have left your comments to 'unfortunately doesn't work that way' !! It might have done the OP a bunch more value had you explained why the wheel choice and tire sizes of poster #2 worked regardless if OP's car was 4 -9.5 @ 38 or 2-8.5@32 originally etc.
OP's response to your 1st 'Well that confuses me even more' - So you come back with Chevy 'centered' and rambled on with actually meaninglessly nonsense.and tossed 315's and 11 inch + spacers. I'd bet you don't actually understand what you typed!!! You tried front spacing several weeks ago and 'blew that'. I can't quite see the relevance of the key is 8.5 @32 & 1.25
To close you might have mentioned why the choice mentioned by '@playdixie' was rational regarding 18" rim choice and what offsets that would have maybe given the OP an idea of what really works.
If you get confused again you might point someone to Joby's for a very good comparison of all C4 wheel combinations. I get offset, back spacing, actual vs advertised rim width
WVZR-1, it seems like you have major problem with me. I'm not really sure when and what I did to ruin your day. If you'd like to tell me, that would be fine, but let's take that out of other people's threads. PM me. Otherwise, get off my back.
There's nothing inaccurate in my responses to the OP here. He asked about a variety of widths and what offsets he should look for. After my first response, he essentially asked why the same 32mm offset is proper for both an 8.5" wheel and an 11" wheel, and I tried to explain why. If you can explain it better to him, please be my guest - whatever is helpful is welcome.
Playsdixie then posted that 18" diameter was a good choice. It wasn't really germane to the OP's questions, and I pointed that out. When someone is asking about proper offsets and max widths that will fit a C4, and someone else replies with a recommendation for wheel diameter, I think it's important to point out that larger-diameter wheels don't really change the offset/width requirements on a C4. Again, if you think otherwise then please bring the tech. If I'm wrong, I'll say so.
Early c4 Wheel offset and width question
