I bought a set of GM stamped satin five spoke wheels that were off of an SS Camaro. They are the same wheels that were on the ZR1 Grand Sport and collectors edition Corvettes. In the MidAmerica catalog, it says that 84-87 require adaptors for 88-96 wheels. I just wanted to know if anyone knew why. I bolted them on and they seem to fit just fine without an adaptor, so I was just curious as to why an adaptor would be necessary.

 

The offset for 84-87 factory wheels is 38mm; the offset for 88-96 wheels is 56mm. The bolt pattern 5x120.65mm is the same so the wheels will bolt on but later wheels (including F-body wheels ) will set further inside the wheel well by the difference of 18mm.

Teh adapters bolt to the hub using the factory studs and lugs and the wheel attached to the adapter which has its own studs. The adapters provide the necessary spacing to get the later wheel to sit out properly in the wheel well.

The 11" factory rear wheel for the ZR-1 has a 36.5mm offset but the rear 11" wheel for the GS is not the same.

I tried bolting on the AFS ZR-1 style wheels from my 92 onto my 87 and thee wheel sat noticeably further inside the wheelwell. The tires (275/40's didn't scrub anywhere but I just drove it around the block so it's hard to say what interference there may have been with tight fast cornering.

Go to the AFS Wheels website http://www.afswheels.com for information on the differences in backspacing between early and late C4's, Camaros and Trans Am's. There is even some offset differences between F-body coupes and verts.

 

Like he said, the adapter plate is needed for the wheel to sit perfectly because of the offset change between the 87 and 88+ years.

 

It's needed?

Well, not really.

I have wheels with the '89 offset on my '87. I don't have the those overpriced ($225?) adapters on my car. This allows you to run 315/35/17 tires without it looking "funny" and sticking out too far. Nothing rubs and it works great.

I know 18mm isn't much, less than 3/4" but with factory sized tires it might not look right. To my knowledge there's no safety issue either way.

BIG JIM

 

I was planning on using these wheels for autocross slicks. And it sounds like everything is going to work out, so thanks for your input.

P.S. Are there any rules about stud length when running slicks for autocross like in drag racing?

:party:

 

You'll have to check with the sanctioning body to see if there's any specific rules about lengths. Our association requires a minimum of 9 turns of the nut from the edge of the stud. We allow either open-ended nuts or acorn style but either type has to meet that # of turns requirement.

Some associations may not permit the use of "spacers" which is simply an aluminum ring with holes for the studs that slips on between the hub and wheel.

 

:iagree:

I had late model C4 wheels on my 84 without adapters. There weren't any clearance problems. As stated the wheels set about 3/4" further in. I liked it that way. Didn't have that ricer offset. :jester

My thought was that I could always buy the adapter/spacers at a later time if I didn't like it. I liked it so I saved a few hundred not buying the spacers.

 

Sorry guys, I have to disagree. When I bolted the later model wheels on my 87, the gap made it look wimpy, kind of like a good lookin' lady with baggy jeans! It had to be filled out perfectly. Of course, when I installed my magnaflows, I couldn't stand they way they hung a little too low. I made my own brackets so it would look perfect. I guess I'm just a perfectionist or a little bit ****. To each their own.