ervinc

first of all i cant edit the heading but is 1/2 over , i hate to see anything obviously out of sync , and looking at the rear of my c4 i'm automatically drawn to the fact the passenger side tire is 1/2 inch further inset than the drivers side which is flush to fender with the current wheel setup i have , i want to know as anyone addressed this issue , i hear its common , i have measured everything and the problem lies in the mount for the bat wing. It looks like i could drop the bat wing and redrill the mounts over a 1/4 inch or get serious and replace the attachments points all together , but i don't want to go that in depth , any ideas or solutions done in the past would be helpful , and this is with 9.5 inch z06 c5 replica wheel . thanks.. also since im planning the mods to install 17x11 oem ZR1 wheels i feel this needs to remedied before starting the big doggie mods .

Churchkey

Sounds like a lot of difference maybe check the backspace on both rear wheels you may have an early & a late wheel they are different offsets.

hcbph

what he said.

If it was mine, I'd jack it up and support the rear on jackstands and take off the wheels. I'd then start measuring everything on it and see if it's actually out of whack or something else.
Another option would be to pay a frame shop to go over it. They should have the equipment and measurements to confirm if it's correct or not.
Another thought might be the car could have been hit in the past and a not-the-best repair was done and the body panel might be misaligned vs the original position.

MatthewMiller

Assuming it's not a problem with wheel offset (see replies above), it's probably aligned properly with the front subframe, and you're just seeing the body that didn't line up properly. The quality control on C4 body panel measurements and alignments leaves something to be desired, but I think the frames and subframes are usually fine. Check with diagonal measurements from front to rear subframe reference points. If they are equal, then leave it alone. If you move the rear batwing to one side, you'll end up with significant thrust misalignment. If it's just the body panels, you can try to get a body specialist to line them up carefully for you.

gerardvg

Hi

First check your rear wheel camber, the offset bolt / washer camber adjustment can move. If one wheel has negative and the other positive camber it can look wrong.

Use a piece of string with a heavy washer and hold to top side of the tire, and see if the camber is ok by gap between top and bottom of tire.

Usually the trailing arms (dog bones) are bent or the bushes are bad, the easy to bend them. just as easy to fix one that is slightly bent.

KSA Aaron

This is very common on the C4 vettes. Assuming the frame is true and square (which I will bet it is), the bodytub was not perfectly aligned with the frame causing the fenders to not set true to the tires from side to side.


You will have big issues if you start trying to move the batwing relative to the frame, as the rear wheels will no longer be true to the location of the front wheels.


Unfortunately, without removing the rear bodytub from the glued mounting to the rest of the body and relocating, there really is no practical solution.

DMITTZ

I've also noticed this about the rear wheels on my C4 and it bugs me also.

In my opinion, moving the batwing mounts is going to be a big project since you will likely have to modify a bunch of stuff to make it work... more trouble than its worth.

Proabbly the best bet would be to just use a 1/2 hub-cebtric wheel spacer on the side that is further inboard to even things up.

Also I don't know if you noticed this but the front wheels (on my C4 stock) stuck out more than either rear ones. That bugged me too...

rocco16

Yep. ^ Providing the camber is correct on both rear wheels, and the wheels are correct, the easiest, cheapest, quickest, best way to correct this is a 1/2" wheel spacer.

MatthewMiller

I wouldn't even recommend a wheel spacer, except maybe for car shows where appearance matters more than function. If you space just one wheel out, you've still jacked up certain aspects of suspension geometry. It would be worse on the front, where you'd introduce asymmetric steering geometry and probably create a pull. But it's also not ideal for the rear.

Again, unless you can actually verify that the subframes themselves are out of square with one another, just accept that it's the body work being misaligned and/or see if a Corvette body expert can address the misalignment.

ervinc

i believe its figured out, i spoke to prior owner, he according to his memory sometime back he had a bad bearing in the rear hub passenger assy , so he got a good deal on a complete hub assy and replace it on the passenger side , he thinks it was from a 87 corvette, which may explain why the 17x11 zr1 wheels were even with passenger side fender but stuck out on drivers side, this is leading me to believe if i can find a 87 rear hub assy for the drivers side i may be able to use my ZR1 wheels and avoid all the machine work for the big doggie mods . wheels are equal in width , all alignments has been checked , all checked good , no drift or pull , just cosmetic. I'll try and locate a 86-87 spindle assy and realign it and see what happens . so much just because i dont like the look of it.. i need to get it figured out or learn to accept it so i can get ready and have it painted this winter.

MatthewMiller

Sorry to burst your bubble, but Autozone and Rockauto both show the same exact rear bearing/hub for a 1986 and a 1996 Corvette: AC Delco 513013. So that's not the issue...unless it's coming apart. I doubt it is, but double check it anyway.

ervinc

the difference isnt the hub bearing but the spindle assy itself, if you look up the article on how to do the big doggie mod, i think it would make more sense, it looks like the early 84-87 spindle assy is narrower than the 88-96 , the plan was to do the big doggie mod and machine work to the newer assy to decrease the width, but if in fact the prior owner used an early spindle assy , half the work is done, at least thats how it appears to me... id rather see im wrong before i spend the money , but it appears thats the issue im having .

MatthewMiller

Oh, I didn't realize you meant the spindle was also changed out. That's...ummm...an interesting way to repair a bad wheel bearing!

As for the "big doggie" mod, I don't really see the point. You can just get 11" or 11.5" wheels with the proper offset and run 315s on the back of your stock C4. You can also run them up front. Why swap spindles and machine parts?

WVZR-1

Check the casting information on the knuckle on your car. I don't believe that what you believe is possible. I don't believe the caliper bracket will bolt directly to the early knuckle allowing the use of later caliper etc.

Here's casting information and location on the later knuckle.

https://www.ebay.com/itm/C4-Corvette...FaD1Vc&vxp=mtr

Early casting likely 14084094 or something very different than what's in the eBay offering.

ervinc

the big doggie mod comes into play to run the oem zr1 wheel, the common 5 spoke replica is available in the offset to run on later c4, but if you really like the 17x11 1991 zr1 wheel which isn't available aftermarket , then you either do the mod or hang the grand sport flares

ervinc

thanks for the insight ,

WVZR-1

If this car were here we'd use a Tram gage from maybe the lower front ball joint fitting to the differential in an X to check actual placement. There wouldn't be a need to do a visit to a collision shop.

What's tolerable to assume it's correctly orientated? No idea but if it were substantially different then you look much further.

Right BJ fitting to left camber bracket or maybe cover left lower bolt and then - left BJ fitting to the right camber bracket or maybe the right lower cover bolt. With the tram gage you could do the X from multiple points.

You haven't mentioned how or what you're measuring but I'm guessing tire sidewall to lip. That doesn't get it! 1/2" sounds like an approximation - I really like Metric dimensions and no approximations.

If you were to want to measure to the body edges I believe you need to use straight edges on maybe the rotor surface. I'd think it easier to set camber to 0 but that would depend upon familiarity of measuring and the devices used.

ervinc

thanks for the input

383vett

Back to the op's original idea about moving the batwing a 1/2" toward one direction. Don't forget that the motor to the rearend is one piece due to the c-beam. They are not mounted separately like a 70's Camaro. The motor mounts are mounted to the frame and the batwing mounts also mounted to the frame. There is no "play" in between unless you are talking about torqueing the rubber motor mounts and bending the c-beam.

ervinc

i may just bite the bullet and straight axle it, i can address all the issues at one time then , yes i know it will be more involved , but i wont be so limited in what i can do , i was planning to replace the dana 36 with a 44 in the future , but even that can be a crap shoot in reliability . thanks everyone for the input, i'm just going to let it ride till i can go to the next stage . thanks again .