For those of you who dont know, you can follow what im trying to accomplish in this thread.
https://www.thirdgen.org/forums/susp...placement.html

However, i thought it best to start a new thread, because i think this is a new topic.

In a nutshell, im trying to make my new 17" wheels fit, and am doing everything to make them work right. Ive already taken care of the studs, now im trying to figure out what spacers to run.

the car has a completely stock, factory suspension, with all that that entails. Now, the car is up on all 4s with jackstands all around. They are supported on the frame, so the rear is dangling.

Ok, so the problem arises, when trying to make sure the car will not rub the wheels with maximum rear end travel. When the rear is at ride height, the bumpstops are in the "valley" of the wheel, and if the springs compress even more, it will stay in the valley. No issues there.

The issue is when the rear end drops. This makes the tire part, and the inner lip of the wheel the perfect height to rub against the nasty corners of the bump stops. Normally this wouldnt be a problem, but to add to this, the panhard bar makes it shift slightly, side to side, depending on the position of the rear, and wants to make the tire rub.

I noticed this, because yesterday i was trying to figure out what spacer to run, and 1/4 in did the trick, on the driver side. Then the rear went up and down a few times, and today i checked again, and it looked like there was lots of room. So i removed the spacers, and it seemed to have the same clearance.......

So my question is, WHERE SHOULD I POSITION THE REAR END TO DETERMINE WHAT SPACER TO RUN? And do i run the same spacer on the other side?

Basically i dont understand why the rear is shifting side to side, and how it will behave.

I can get pix if needed, sorry for the wordy descriptions....

 

the rear will move side to side when you drop the rear. when you are driving it will also move, but just a little. Do you have an adjustable panhard? What i would do is raise the car by jacking up on the diff, thus keeping the suspension loaded, then you can measure and find what you need. If the let the rear drop, them measure, it will all change on you when you put the car back on the ground

 

You had two questions so I will give you two answers.

Why does the rear end shift side to side?

Stand up and go walk up to a wall. Stand just far enough away so that the tips of your fingers barely touch it when your arm is extended 90 degrees.

Move your arm up and down. See it no longer touches the wall. remember this.

The panhard bar is your arm, the point where it mounts on the chassis is your shoulder, the tip of your finger represents the movement of the axle, the wall is your bumpstop.


Where do I measure the wheel clearence?

So you want to set your ride height and measure your wheels with the panhard bar level.

I would not worry about the spacers. The only time it will touch is when the suspension is at full droop.

If you jack up the car by the rear end to change tire this will never be a problem
What size

 

Ok, thanks for the arm and wall analogy. I kind of had that idea, but wasnt sure which way it would behave.

86TA; its a factory panhard bar.

Are you sure i can set it while its on the ground? If the rear end shifts more than 1/4 inch while driving, i will have rubbing.

Also, i dont plan on jumping over cars like in the dukes of hazard, but i did have a fair bit of suspension travel when driving spiritedly on a "hilly" road. Not to the point of full drop, but still quite a bit of travel.

Would i be ok in that scenario?

 

I think a 1/4 inch is a little low on the clearance. What will happen when you go over a bump with one tire and the whole rear tilts to the side. I think you will have rubbing. Why don't you moddify the inner wheel well by removing the bump stop.

 

i had about 1/2" of clearance and i rubbed on everything, you need more

 

Crap, thats not what i wanted to hear..... Ill see what i can do.

 

what wheels/tires are you using and have you done any mods to the inner wheel well yet?

 

Im running these. I was told they are one of a kind, or atleast very few in number. Originally made for a BMW, modified to fit a thirdgen. They are 17x9.5 with Falken ZIEX 512, 275/40/R17 tires. I dont know the specifics of the wheel, but it has a good 3" in lip in the front, so im guessing the back spacing is roughly 6?

In any case, the car is completely stock, in terms of suspension and chassis. No inner fender mods or anything. I had a closer look today, and i say ill have to agree with you guys on the "spacing". I compressed the springs all the way, jacked up on the diff. Put on a 1/4 in spacer, and it will still hit the bump stop.

So i asked a freind if i can borrow his wheels for a couple weeks, and i will get the bumpstops removed when i get my SFC's installed. Im not skilled enough to do it myself..... And i dont have a welder.

The last owner had these on his slammed, (like 1 or 2 inch clearance from the front air dam) 91 GTA, so i thought they were a direct fit. But they also had huge gashes in the rear tire, so.....

The pix dont show much, but in the last pic, you can see the original berlinetta 14" wheels (195/70/R14) from my old camaro, and the 17x9.5s on the driver side.

 

sorry i don't have anything important to add, but what an attitude adjustment in that last pic!

 

I did not know what wheels you were running when I made my comments.

What is the backspacing? if you space it too far out then the tire will be rubbing the fender.

backspacing of 5.5 works well for a 17 X 9.5 wheel and a 275 /40/17 tire.

 

Like i said, i think its roughly 6. AS they sit, they "tuck" pretty well, but i will be rolling the fender lip just incase. If it werent for the bupstops, i am extremely happy with the way they tuck.

I will get an exact measurement later on, and let you guys know. They are under a bunch of tires right now, and i dont feel like moving them.

 

Gonna revive this thread...

i didnt get around to having the stops removed or the sfc's installed, because i decided to paint the car... Will have to happen in the spring. In the mean time....

What would happen if i limited the "drop" of the axle some how? With a chain or something. So it could compress all the way, but would only drop a couple of inches, as to not rub on the wheels? Im trying to avoid removing the stops if at all possible....

 

How much do they rub? Can you trim the outer side of the bump stop?

 

So it would rub about 1/8 to a 1/4 inch max. ie; if it were possible, thats how far the wheel would go "into" the bumpstop. Both tires wont rub at the same time, i can get away with it with very little clearance, which was my plan. But i got worried when i learned the rear end actually shifts side to side.....