Evolution1980 said:
I'm kinda fuzzy on this whole thing too. Set me straight, if I'm not already... actually, rather than me say what I think everything is, how about someone just explain wheel spacers and offset TA's... please? :confused Thanks in advance...
The 84 to present vettes have a positive offset. This means that the point of the wheel that bolts to the hub bearing is more outward, and the rim itself is more flat looking (less dish). The pre 84 vettes have a negative offset meaning the bolt hub portion of the rim is closer to the inside of the car and thus you have a more deep looking dish to the rim. For example, my back wheels on my 69 are EXTREME deep dish.
Now, the adapter/spacer is like a thick washer drilled out to offset you wheel studs and line up new wheel studs for the replacement rim. It "pushes" the offset of the C3 out so that it mates up with the mounting zone found on the newer cars.
It just so happens that the last gen F body and Vette can interchange wheels as they use the same basic offset.
So, that means on the C3, you can run the F body wheels or Corvette wheels as long as you install a spacer kit to move out the mounting point to a more positive offset. Also, 84-87 Vettes have less offset than 88-2003. So, if you happen to get a set of stock or custom wheels that came off a 84-87 you have to specifically get adapters for those year wheels to go on your C3.
On the trailing arms (yes, they are hard to replace as 99% of the time the mounting hardware has rusted solid, and you end up with a full rebuild of wheel bearings, e-brakes etc). The stock rear trailing arms would be that bar like thing that comes out of the frame just behind the doors and reaches to the wheel. This is the pivot mount for the whole rear end. It has a bushing up in the frame and you set the toe on the alignment by stuffing shims in and out of each side of that bushing. The other end of the arm supports the wheel bearing, shock/spring mount, and wheel. The stock unit runs the e-brake cable on the outside upper part of this trailing arm. If you go with a more positive offset rim and start pushing the inner part of the rim closer to the frame of the car you can end up rubbing the e-brake cable. Most people just cut the e-brake cable mounts off and push it aside as the e-brake does not work anyway. Others will weld the tabs back on further inboard to clear the wheel. Finally, others will go with aftermarket trailing arms that have a offset cut in them and the cable mount relocated so that you can squeeze another inch of rim in the car without hitting anything.
Consider this. The C4 rim is 9.5 inches. That means lip to lip it is about 10.5 inches wide. Your stock C3 wheel is 8" which means lip to lip it is 9" wide. You can gain 1.5 inch of rim with the C4 wheel and spacers. That 1.5 inch has to go somwhere. In this case the spacer will help split the difference so that you gain a little outbound and inbound width.
I know several people that have done it on stock trailing arms and have had no problems. Now, if you go to ZR1 rear rims. Those are 11" wide or basically 12" wide lip to lip. These are going to give you some trouble if you don't mod the trailing arm and maybe even trim the fender lip a tad.
Hope that helps.
