I have an 85 and bought ZO6 rims and 3/4" adapters which several searches on the Forum indicate are needed. The adapters would work well with a rim like my current sawblades which have a large space on the back side for the nut on the adapter to protrude into this space. The ZO6 rims do not have this much space, so the adapters won't work. I put the wheel on the rear end and it looks like there would be not problem with a direct bolt on here. The front end is a different story. Sawblades have about 1" of space at full lock and ZO6 wheels about 1/4".

Would this indicate that spacers are only needed on the front end?

I will be calling a couple of companies about the availablity of spacers in the morning. Any help you can offer....

Thanks

 

I thought we discussed this. You can't use adapters thinner than 1-1/8" with most reproduction wheels because the studs stick out too far.

Which size wheels are you using? 18x10.5 & 17x9.5?


I'm not exactly sure on the spacers needed with Z06 wheels. I think that 10.5s will fit without any adapters, because they have the same frontspacing (mounting surface to outer face) as stock 84-87 wheels. Noone has agreed with me on this yet.

 

Here's an old post of mine that should help... according to this, z06 rears are bolt-on, and z06 front could use a 1/4 or 1/2" spacer if anything. 1/2" spacer may be pushing the issue. Using excessively long wheel studs for those are quite safe in my opinion.


from archives...

Here goes. I call this figure the "front spacing" it measures from the hub to the outer bead and determines the placement of the wheel relative to the wheel well. You find it by subtracting the offset from half of the wheel width. For a zero offset wheel, this distance is just half the wheel width, got it?

The outer bead is about the same 3" out from the mounting hub for either wheel in question.

84-87 base wheel, 16x8.5x32mm
8.5"/2 - 32mm/25.4 = 2.99"

Z06 rear wheel, 18x10.5x56mm
10.5"/2 - 58mm/25.4 = 2.97"

Also note that the z51 wheel sticks out 1/4 inch more than the base model...

84R-87 Z51 wheel
9.5"/2 - 38mm/25.4 = 3.25"

And some other wheels,

lateC4 wheel, front (opt. 8.5") and rear:
8.5"/2 - 56mm/25.4 = 2.05"
9.5"/2 - 56mm/25.4 = 2.55"

C5 base model, front and rear:
8.5"/2 - 56mm/25.4 = 2.05"
9.5"/2 - 65mm/25.4 = 2.19"

Z06 front wheel,
9.5"/2 - 54mm/25.4 = 2.62"

Please correct me if my numbers are wrong, it's hard to find a reliable source of info.


There is no magical number that makes it look right, it's a range of frontspacing for each set of vettes, some which come close to overlapping other years. But looking at these numbers, you can get a good idea how thick a spacer or adapter you'd need to get in the ballpark. I mounted C5 fronts on my 85... 3.25"-2.05" = 1.20". So I used 1.25" adapters and they fit perfect.

 

17x9.5's. I really did an extensive search before I did all of this. The nut on the adapter that screws onto the existing studs would have to be machined to remove about .375 to fit into the existing space on the ZO6 wheels, that is using the 3/4" spacers.

Any idea about the rear end? Looks like lots of clearance.

-John

 

Check out the open ended lugnuts at pepboys. They're as small as they come. That's what I use. Any smaller and it'd be tough to get the lugwrench on them, they don't stick out of the tapered holes much more than 3/8".

Do your adapters have conical tapered lug seats, or flat seats with washers?

 

Looking at those numbers, .75" adapters don't put you much further out than the factory Z51 wheels.


9.5"Z51: 3.25-2.99 = .26"
9.5"Z06: 2.62-2.99+.75 = .38"

That's only an 1/8th of an inch further out, at least based on the mfg specs. I don't know if there's a standard distance from bead to outer face or if it differs by wheel and needs to be considered.

 

From your formula stock 2.99, the 17x9.5 are 56mm so....56/25.4=2.20.
That would give you 2.99 - 2.20 = .79 or close to 3/4". The spacers are the later, dished out space with large washer and LONG nut. I think that 1" would work depending on what type of nut us used to attach the spacer to the existing studs. If it sits flush to the adapter or extends about 1/4" it would work. Looking at the web site for "A-DAPT-ITUSA", it looks like their adapter would take stock lug nut and sit close to flush.

 

Even if you get adapters with tapered holes, the studs will stick out 3/8" (and more for some replacement wheel bearings). Can your wheels accomodate this? I thought mine could, but they just barely don't, and I've had headaches with wheels coming loose, and grinding the wheels and studs over and over again. I shoulda stuck with the 1.25 adapters.

 

Central, since your pretty familiar with the wheel specs, I also have an 85 with c5 wheels on my car With spacers on front/rear. They work just fine,----but I have a 383 and other performance giving some more hp/tq to the rear wheels, my local shop told me if I go with the 3:73 rear gears that down the road the REAR spacers will eventually get shot. due to the cheap metal the spacers use. Are the rear spacers required for the rear wheels, I just gave the spacers and c5 wheels to a differ mechanic and he put them on, but he didn't recall whether the rears were needed....

 

I ordered 1" adapters this morning. The lug nut that holds the adapter to the original stud will sit flush with the adapter or be a little recessed. This is acceptable with the ZO6 wheels. The original studs may go beyond the adapters about 1/4". I won't know for sure until they arrive. I think that 1/4" would extend into the wheel recess okay. If not, then I put a die on the stud and use a cut off wheel to shorten the stud just a little and then run the die back over the the threads restoring them.

Thanks for your help CentralCoaster. There are times when you research and plan and it still goes to S**T. There just wasn't any way of knowing what the recess on the ZO6 wheels were until they arrived.

 

Do your adapters have conical tapered lug seats? Are they hub centered on the car? Do they have hub extensions for hub centering the wheels?

All of those are preferred, but 2 out of 3 ain't bad either.

All the adapters I've ever seen claim to use 6061 aluminum which is perfectly adequate if made right. You'll break a halfshaft before you break a wheel adapter.

I would really just be careful about checking adapter lug tightness, and snugging them evenly. And put some antisieze between the adapter and the steel rotor hat.

Now, spacers on the other hand, increase your chances of snapping a stud, or a stud coming loose because more of the stud is stressed. I think they've used spacers in Winston Cup though.