I want to use 17's off an 89 on my 85. I test fit them and they rub because the offset is different. My only option I guess is wheel spacers but I have read mixed reviews about using them. Has anyone else put 17's on their 85 and what size wheel spacer will work?

 

I just put 1990 wheels on my 85. I bought 20mm spacers and they fit snuggly on the hub, and the wheel sits just at the edge of the wheel well.
I purchased the spacers here: https://www.ebay.com/itm/2X-20mm-5x4...72.m2749.l2649

 

Just make sure they are hub-centric spacers. Torque to spec and re-torque after a 100 miles or so. Some will argue that they are not safe, but for normal street use you should be fine.

 

Spacers and adapters are safe if used correctly. You should only use about a 1/4-3/8" spacer with standard lug studs. Anything more then you need longer studs. Just make sure the lugs have enough turns on the stud to be safe.

The other option is adapters. They bolt to the factory hub and then have new lug studs to bolt the wheel to. Torque the lugs on the adapter just like you do a wheel. Then torque the wheel onto the adapters. I've been using 3" wide adapters on my 73 and 76 for nearly 20 years with no issues. I put 16, 17 and 18" wheels on my C3s.

 

I put the late staggered wheels on my '85 for a while. I had a set of 1.25" adapters so I tried them. I had these because the stock lug studs are that long and I didn't want the studs sticking through the adapter and possibly interfering with seating the wheels. (The stock late wheels I used have some clearance in this area and may have fit with a thinner adapter, but all wheels may not. I do not know about the '89 wheels you are considering.)

The fronts had 8.5" wheels and they fit fine. If they were any wider I think they would have stuck out too far, so I never tried the 9.5" wheels on the front.

The rears had 9.5" wheels and fit fine. They came out to be flush with the outside of the body.

I put them on and then retorqued them after a hundred miles or so. I also retorqued them again after another hundred miles or so and had very slight lug nut movement, so I am glad I did it twice.

I ran these wheels for a few thousand miles and never had any issues.

Good luck.

My '85 with adapters and staggered late wheels is shown below.

 

^^^ All of this. This is the perfect post on this topic. And I agree, if I were doing a 3" spacing, I'd use adapters too because I seriously doubt there are any wheels studs long enough to make a 3" spacer work! Otherwise, plain spacers work great as long as the studs are long enough. IMO they are probably actually safer than adapters because they cannot possibly break or otherwise fail, they don't have to be hub-centric or otherwise carefully made (the only dimension that matters is that they are flat), and they are cheaper and lighter than adapters. Maximum Motorsports has a great article written by their development engineer (a real, actual engineer) that discusses how spacers really work and why they are safe.

To the OP's specific situation, the early 16x9.5 wheels had 38mm offset, whereas the later 17x9.5" had 56mm offset. That's a difference of 18mm, or about 3/4", which tells you the thickness of the spacers you're looking for. You have plenty of room on the outside (assuming a 275/40/17 tire, which is what you should use on that size wheel) to use a 1" spacer if you prefer. It will look a little more aggressive that way, at the expense of a bit more scrub radius. So anywhere from 3/4-1" spacers are what you want. You'll want longer wheel studs, and ARP (among others) has those readily available. They aren't hard to install.

ETA: If you're looking at staggered-width set of later wheels with 8.5" fronts, then the early 16x8.5 wheels had an offset of only 32mm, whereas the later 17x8.5 (93-96) still had 56mm. So in that case, you have a 24mm difference in offset, so you should look for 24mm or 1" spacers for the front, and probably 3/4" for the rear if you want to keep the outside edges of the wheels in the stock locations for your 85.

 

I should have used the proper term, I bought hub centric adapters for my 85. They bolt to the hub using the lug nuts on the hub with the centers machined to fit snuggly on the hub. The adapters are torqued to 80 ft lbs and the wheel mounts to the lugs on the adapter.