OzzyC4

In reading another thread about wheel fitmanet on early C4's the topic of wheel spacers comes up.
A spacer of 20mm would move the wheel back to the proper backspace if I follow correctly.
My questions are what is the safety effect of using spacers?

20 mm is .7873992 inch. A spacer of this thickness must just slip over the wheel studs.

IF so, are longer wheel studs required or are there deep lug nuts for this application?

Realizing that different wheels are built a bit different, I would think it is possible to take a set of 20 mm spacers and mount them to the inside of the wheel by drilling and tapping some blind holes in the wheel and using countersunk screws through the spacers. This would secure the spacer to the wheel for nothing more than ease of installation and keep the spacer with its wheel as a balanced unit.

If my theories are correct, then it looks like I will be spending some time at my friends lathe and mill building some 20mm spacers.
I just have to have(lol) some chrome Z06 wheels on my '87 when I get back to work in the spring.

CentralCoaster

No, you don't use spacers, you use adapters. The adapters bolt to the hub, and the wheel bolts to the adapter.

Spacers are junk, and I would not feel safe with one on my car, unless it was hub centric and less than 1/4"

drvn2fast

jerryL98

Sometime the words spacers and adapters are used interchangably though. But I agree, use adapters.

kdf1986

Hello,
I have a 86 that I installed C5 rims on. So I had the same as you. I think that the wheel offset changed over in 1988, and the years after that do not need adapters. Also, use adapters not spacers. They terms may be interchangeable when talking about this, but you do not want to use something that thick ( 1 inch ) that slips over the studs. You want something bolted on.

The way it works is that you will bolt the apaptor onto the existing lug nuts. The adapter has lug nuts installed inbetween the existing pattern. Then you bolt your rims onto the adaptor. That way everything is nice and tight.

When I was doing my research I found this website.

http://www.racehome.com/techwheelfit.htm

It has photos of someone doing the same exact thing and how they installed the adapters and rims.

For the adapters you will be better off buying them from a catalog than trying to drill exisiting rotors and making them yourself.

Good Luck.

kdf 1986 L98
kdf 1973 454

kdf1986

I reread my thread and found that I cant type worth a darn tonight. Its ADAPTERS not any of those other spellings.

I do like to sound literate every now and then.

kdf 1986 L98
kdf 1973 454

Vetteboy77au

I notice on that link that the wheels that guy uses has recesses for the heads of the nuts used to hold the adaptors onto the hubs.... are these necessary for a 3/4" adaptor?

If so, does anyone know if these are on the House of Wheels or OE Concept rims?

Thanks

Chris

c4cruiser

Most aftermarket wheels do not have recesses in the whell mounting flange. The adapeters I have seen for use on 84-87 C4's use an acorn style lug nut to attach the adapter to the hub. If the adapter is the typical 3/4" size, then the acorn nut will stick out from the adapter face. Original GM wheels have recesses built into them so using a set of real Z06 wheels should work.

If somebody uses adapters, maybe they can tell you whether or not the mounting stud on the hub protrudes thru the adapter. If it doesn't, then maybe a set of standard open-end lug nuts can be used so that the adapter can be bolted on but nothing would stick out. You would also have to know what type of lug nut be used to dothis. GM lugs are 1/2x5mm with a 60 degreee taper. If that's what the size of the adapter nuts are, you can get standard nuts anywhere.

If the stud sticks out beyond the adapter, it might be possible to trim the stud, but I would not do that if it was my car.

Also check with AFS wheels to see if their Z06 wheel has recesses on the flange.

Vetteboy77au

Does anyone know the stud length from the mounting face of the hub/bearing assembly?

Thanks

CentralCoaster

Mine are 15/16". I have 1" adapters and the studs do not stick out passt the mounting surface.

You should measure your studs though, these exact same adapters didn't fit on another forum member's car. I presume he had replacement wheel bearngs that have longer studs.

86PACER

True. The original owner of my 86 replaced just one rear wheel bearing assembly long ago. Both sides of the rear have different length studs.

kdf1986

I replaced my 86 rims with C5 rims. Maybe from a 2001. The wheel adaptor that I used was a 1inch thick billet aluminum piece. The adaptor was held in place with acorn nuts. The C5 rims have the recess in them for the acorn nuts to sit inside of.


kdf 1986 L98
kdf 1973 454