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I've heard some conflicting info here and a search just made it more conflicting with multiple answers.
I'm told the later C4s had a wire rear track. I first heard this when looking for wheel fitment issues and some said that spacers would be needed for an early C4 but not a later one. Then I was told it was only the D44 rear, and then again only on the ZR1.
Can someone clear this up? I want to put C6 Z06 wheels on my 89. The rears are a 335/40/19 on a 19x12 wheel and they hit the frame rail. I was going to get 1.5" aluminum spacers that bolt to the hub and use their own studs, but I'm not sure I feel safe taking a 100+ mph corner with those.
Can I swap from my 89 D36 to a later D44 and have a wider hub-to-hub width to allow me to skip out on the spacers?
I had put C5 18" aftermarket wheels on my '89 C4. I was told 19" wouldn't go on.
The 18" went on w/o hitting the frame. Not sure of the offset of my C5 rims, tho. Plenty of clearance, worked and looked just fine.
ZR-1 is wider. You might have to locate a ZR-1 fender flare kit. Or, buy a ZR-1.
Body panels are a non-issue since my car doesn't have any. I only need rear end specs. Is the ZR1 rear itself wider or just the body panels? Are there any non ZR1s that have the wider rear?
First, the suspension changed in 88 so your 89 already has the same suspension as later cars.
Second, wheel offset and backspacing has more to do with how wheels fit than the track width you are talking about. Your stock 89 wheels are 9.5" wide with a +56mm offset. This makes the backspacing 6.8" (wheel width / 2 + offset). The Z06 wheels you have are 12" wide with a +59mm offset. So the backspacing is 8.3". This means the backside of the wheel sits 2.1" further towards the frame than your stock wheels. Hence the reason the Z06 wheels are hitting the frame. So you need to take up the 2" of space to move the back of the wheel out to where it should be.
To put that into perspective, my dad has a 90 ZR1. He was using 335/30-17 tires on the ZR1 rims. He then put the same tires on a set of 96 GS wheels and the tires hit the trailing arm. This was because the ZR1 wheels have a 36mm offset where the GS wheels have a 54mm offset. This caused the wheel to be 18mm (3/4") further inboard causing the rub. So, the same rim width with a different offset can mean a rim won't fit on the car.
Using an adapter (not spacer) is perfectly fine. I've used them on my 73 and 76 for 20+ years with no issues. My dad uses them on his 90 ZR1 when he uses some 18x12" wheels on the rear. We autocross and do some track events. Just make sure to torque the adapter onto the hub just as you would a wheel. If i were you, i would get some 2" adapters. The 1.5" ones you talked about "may" work, but the 2" would be safer.
I understand wheel fitment, but I was told at some point that the hub-to-hub width of the C4 rear end was different and I wanted to see if I possible had an upgrade option that would allow me to avoid spacers.
I'm worried about using aluminum adapters on a car with close to 1000 HP that might be expected to pull 1.4G in a turn.
I'll buy the 2" adapters and run them for now. Eventually I'll just have to shell out money for track wheels/tires that fit without them. I have until probably July to worry about that.
I'll buy the 2" adapters and run them for now. Eventually I'll just have to shell out money for track wheels/tires that fit without them. I have until probably July to worry about that.
running 1k hp and on a track, why not go with a truck rear end? (depends on the track - drag racing?)
Spacer is just a spacer. The studs pass through it and you bolt the wheel up on the outside of it.
Adapter bolts to the hub, and then has its own studs in it for the wheel to bolt to. This is because factory wheel studs aren't long enough to go through a 2" spacer and a wheel and still thread on lug nuts.
DO NOT use more than a 1/4" spacer on stock lug studs. Anymore than that and there isn't enough thread engaged with the lug nut to create a safe mating. The other option is to use a larger spacer, but also change the lug studs to a longer and stronger version.
Just a suggestion, but I would get an adapter that is hub centric and not just lug centric. The little ledge around the middle hole in the above picture is an indication it is hub centric. That little ledge provides a more sturdy base that can handle more load.
I definitely would not. If you have that amount of power and cornering ability, I would think about changing to 1/2" studs.
The traction control keeps the power nice and linear, and the boost controller will be redone to work on G-forces so I can maintain a G within the tire's ability to grip. I'll likely upgrade to 1/2" studs when I swap to the D44, but I haven't pushed it hard enough on the D36 to break anything yet. The rear of the car is so light I can pick it up off of the ground when the gas tank is empty, so I'm basically relying on downforce at speed for traction.
OP - I see things way different than you've mentioned. You mention being only concerned with suspension/side member interference so assuming that the 11" GS wheel with a 7.9 back-spacing (50mm offset) generally has no interference 11 + 1 = 12/2 = 6 + 1.9 (rounded down).
If your 12 wheel is stock offset 59mm then the wheel would be
12 + 1 = 13/2 = 6.5 + 2.3 (rounded down) with a 8.8 back-spacing calculation.
Since you're only interested in "off the suspension/side member" you need something +/- .9 inch.
You could do that easily with a custom spacer (not adapter) and change your wheel studs to 1/2" or better 14mm at the same time I believe. Your spacer needs a counter bore to match the hub flange diameter 70.3 and depth to allow full seat to rotor.
I and several others run spacers of 16 - 18 mm on our ZR-1 to use 50mm 11 GS wheels vs the ZR-1 36mm wheel with longer over the counter studs. Some think they're performance studs but they ain't. They're nothing special other than just longer.
If your 12" wheel is something other than the 59mm offset then all this is BS. OFFSET should be on the back-side of your wheels. Post that number.
I would do 14mm wheel studs I believe and while not maybe easily found - I ain't looked you could consider just buying 1" adapter style spacers for fitment to confirm all of this works.
Only thing I didn't calculate is the sidewall difference and generally that's inconsequential.
You've got tires/wheels -- a pair of 1" "adapter style" will put you rolling and who knows you might be happy as he!!.
I don't know where you got these crazy 1.5 - 2.0 inch needs.
In post# 8 you mention understanding "fitment" - I don't think so!!!
Because I couldn't run anything larger than a 1/2" spacer on stock studs and I didn't want to chance a thin 1" adapter, so it was 1.5-2" for safety.
You can't run 1/2' on factory studs either!! You really don't seem to get it. 1/2" spacer on your studs would leave you no hub diameter to center the wheel. If you buy 1" billet adapter style from a quality vendor you should be good for at least fitment and until you want to do a more tailored setup.
If you've really got all of this power you mention it might be time to do the 14mm hardware. 5/8 might be easier to get your hands on but for the stud splines you'd need to drill/ream for anything greater than the 12mm.
01-02-2018, 01:19 PM
Rear track widths, later C4 has a wider rear?
