I am looking at getting a new set of wheels for my 1987. It finally got back from the paint shop, though not everything is done yet, so I have some time before it will hit the road.
There really aren't many options available out there that will match the OEM offset requirements, so I have come here to ask if anyone knows what is the lowest amount of offset you can run in the fronts and rears. The intentions is to have flush fitment on both the front and rear, so i really dont want to have the front wheels peeking out too much, if at all.

I do have a set of wheels in mind, they are:
Front --> 18x8.5 +35mm
Rear --> 18x9.5 +22mm

Though I would absolutely prefer to have a square setup, being 18x9.5 +22 around all four corners. If you think this is possible without sticking out, please let me know.

 

The standard wheels are 9.5x16 with a 38mm offset or in some cases the fronts are 8.5x16 with 32mm offset. The fronts are pretty close to inline with the edge of the fenders and the rears are a little further in. In both cases I think those wheels would fit and look ok. The fronts will stick out 3mm more than standard but that’s nothing. The rears will be 16mm closer to the fenders but I think they will fit and look pretty good.

 

First thing first: on any non-ZR1/GS C4, what fits within the fenders in back will also fit up front. These cars have a lot more space for wide wheels/tires up front than most people think. I ran 11s with 315 tires up front on my 96.

Next thing, 84-87 C4s had different offset requirements than later cars, because the width between their hub centers is about 36mm narrower than later cars. So they use about 18mm less offset front and rear than later cars. As noted, your car would have come with 16x9.5 et38 rear, and either those or 8.5 et32 up front (depending on if Z51/Z52 or not).

A completely flush-to-the-fender edge fitment on your car would mean about 4.75" of wheel width on the outside of the hub face (what I sometimes informally call "front spacing" because it's the flipside of backspacing). The 18x9.5 et22 wheels you're looking at will have their outside edges 4.38" from the hub face, so with proper-sized tires (275/35/18) they will still be just inside the fender edges at the top of the arches. That's 16mm further toward the outside than the stock 9.5s, but there's enough room inside the fender well to accomodate. I believe they'd look really nice that way. You will gain 16mm more scrub radius than these cars already came with, which means the steering forces may get a little more extreme and forces such as tramlining will get stronger. You also increase the forces on the wheel bearings by moving the center of the contact patch further way from their centers (increasing the leverage the vertical tire loads have on the bearings). I don't know how serious these effects will be - probably not terrible, but noticeable. But that's just a guess.

Remember the spacers act to subtract offset, and there have been lots of wheels made with more offset than your car requires. So for example, you can use a set of 17x9.5 et56 wheels from an 88-96 Corvette ("salad shooters" or "sawblades") with 18mm (3/4") spacers, and they will sit in the stock locations on your car. That requires extra expense and/or work ("pass-through" spacers or adapters), but opens up a lot of options.

 

Maybe the 'simple' is sometimes not so obvious! You're at an advantage vs many in that you've presented a wheel that 'pleases you'! Determine what's on the car currently(important) and base everything from that.

Drop a string from the hood edge and the rear quarter edge and measure your current outer rim edge to the string. Compare your desired wheel to what's present and measure. If your current rears are 9.5 @38 and the 9.5 @22 outer rim edge is actually 16mm further (MM & I agree) further when mounted, you visualize/determine where the newer will be positioned. Maybe to simplify things move the rear to the front and duplicate the measurements.

There's much information in post #3 that's irrelevant and shouldn't concern you. You're interested in a "SINGLE CAR' - 'YOURS'! A string w/weight and a measuring device answer all questions.

If perhaps those on your car are 'other than' stock then you need to do a comparison vs that wheel. I'd think the 9.5 @22 should work well. It's an unusual presentation so maybe you could share brand & style!

****Are these wheels 'local' or something you're wanting to buy for ship maybe w/tires?

If it's the car in your 'avatar' it doesn't appear to have stock currently. What are they now?

 

This is exactly the kind of answer I was hoping for. I was trying to do some measurements by myself but since the stock tires "bubble" out so much, it is really hard to get a 100% measurement. Thank you for doing the math, the only thing I dont understand is why you would use a 275/35/18 instead of a 255/40/18. Looking at site like "willtheyfit" shows that it might be a better match to the stock sizing. I do have the 16x9.5 +38 all around on mine currently btw.

 

The wheels I am looking at are the "Revolve APVD No. 1219". I am aware that they are drilled to a 5x120 bolt pattern, but I do see that a lot of members run it without any issues. The car in my avatar is just some Japanese BSM Corvette, I will have to get a good pic of mine once it get puts back together in a couple week.

 

5 X 120 makes these wheels a 'NO GO'!!! End of conversation!!!

 

Like I mentioned earlier, I am not worried about it being 5x120. The car isnt hitting the track or dragstrip, it is a daily/cruiser. I know there are wheels that are drilled to 5x120.65, but most, if not all of them, just arent my style whatsoever.

 

For a 18x9.5 wheel you could use either tire size. The 275/35 will be 20mm wider and bit shorter. Either is size is recommended for that width wheel and is within the OE diameters for C4s. It would come down to the availability of tires you want and the width/height you'd prefer.

However, I do agree that I wouldn't get wheels that don't have a proper 4-3/4" (120.65mm) bolt pattern. I know opinions out there differ, but wheel attachment is about as "mission critical" as it gets and I wouldn't play around with it. This where my previous comment comes in: Remember the spacers act to subtract offset, and there have been lots of wheels made with more offset than your car requires. There may not be a lot of options in the proper bolt pattern with offsets in the 22-38mm range, but you can get wheels with more offset than you want (which are more common) and use spacers or adapters to make them fit your car. If you like the split-five-spoke design of the Revolve wheel you cited, then for example you could get reproduction C5 Z06 rear wheels that are 18x10.5 et54, and use a 1" spacer or adapter to make them fit.

 

If i'm not mistaken, aren't most corvettes lug-centric. If so I can understand how some people wouldn't run any 5x120 wheels, given that they are held on by just the lugs.
But if I was to get a hubcentric spacer, wouldn't that take some of the stress off of the lugs? Obviously it wouldnt reduce the fact that the bolt pattern is different, but it could help I think.

 

Not really. The studs/lugs don't actually do the job of holding the wheels in a centered position: once the lug nuts are tightened then friction between the hub face and wheel surface is what does that. Hub centricity doesn't change that. In the case of 20mm bolt patterns, then a hubcentric wheel could at least prevent the wheel from moving off center when you torqued the lug nuts. And I'm not clear on how a hubcentric spacer would help, because that still wouldn't prevent the wheel itself from slipping off center as you torque down the lug nuts. Besides with only 22mm offset, you won't really have space for much of a spacer anyway if you want to keep the tire from poking outside of the fender.

Maybe you meant a hubcentric ring? Is such a thing available for those wheels? If so, it would then act just like a hubcentric wheel. However, you'd still be torquing the lug nuts down to spec and wearing the tapered seat into an oval shape. No spacer is going to change that.

 

Whoops, I definitely meant a hub centric ring. Looking on ebay I was able to find a 73.1 to 70.1 ring. Which would work because the wheels I am looking at have a Hub Bore of 73.10. If I am not mistaken the c4s have a Hub size of 70.1. I would link the ebay listing but I am not sure if that is allowed here.

The idea of using the rings is mostly just to promote the mounting face to be as flat and centered as possible against the mounting surface.

 

It would help keep the wheel from slipping off center radially, yes. What it won't do is prevent the tapered seats in the wheels from wallowing out in a slight oval shape, or the studs from having a bending force. Neither of those is good, even if just 0.65mm. I'm sure lots of people have done this and lived to tell the tale, but I don't recommend it.

 

Wow this has got over complicated. In post two I explained (in one paragraph) that the fronts will be 3mm closer to the guards and the the rears will be 16mm closer to the guards (than stock) but in both cases they will fit. The advice in post four to check with a plumb bob is a good way to confirm.

 

Well the complicated part is that they're the wrong bolt pattern.

 

seriously. That actually makes me laugh out load.

 

If your 87 has the same suspension as my 86 I can tell you what I did. Mine came originally with 16"x9.5" 38mm rims on all 4 corners with 255x50/16 tires. When I replaced them I got some 18"x9.5" 40mm reproduction C6 Z06 rims and put 255x40/18 tires on them. Fit just fine, no rubbing nor issues with them. The rims I got have the proper bolt pattern so they fit just fine.
If you're interested, PM me and I can send info on where i found the rims. Be aware that not all places that list rims in this size actually can get them DAMHIK, I had ordered some from another place and the order was cancelled because those were unavailable.