As some of you know, i recently finished a 4 corners suspension rebuild on my '94 LT1. Today, i began adjusting the Van Steel sway bar link lengths for the sway bars. To have the suspension loaded with the wheel off, prior to making the adjustment, i used a 6x6 inch wood block to support the front driver's side lower A-arm which had a 1/4 inch less clearance to slip the block under the A-arm so i jacked car up just enough to slip the block under the A-arm. After adjusting the link, i moved to the passenger side to adjust that link. Prior to jacking the car up, i slid the block under the passenger A-arm and noted that there was about 3/4" of air between the lower side of the A-arm unlike the driver's side needing to be raised a 1/4 inch to put the block under the A-arm.

My two questions are:

1. "Should the distance from the bottom of the A-arm for both sides of the car be equidistant?"
2. "Or, is it not a concern that the distances are unequal?"

The concrete floor of my shop is flat without irregularities.

Thanks in advance for your help.

Ps. i will post this on my suspension rebuild thread for continuity's sake.

 

The A-Arm should about be level at ride height, measured at the center of the bolt inboard side, and the top of the forging right at the ball joint (about center of the LBJ ball) outboard side. Both sides should be the same. Don’t use the frame cross bar reinforcement for measuring frame level, use the lower deck of the K-member.

Assuming you have coilovers… if there are differences, you can determine if it’s in the upper frame coil over attach point (frame), K-member, or the location of the upright (determined by how far the LOWER ball joint goes up in the hole, and how long the ball joint is when it’s loaded). Another factor is if the coilovers are not setup the same.

BTW if car is lowered much the A -Arm angle will be off but most will not correct it as it’s not easy. Off too much and the geometric front roll center will be below ground.

 

Steve, I'm honestly having trouble visualizing the full procedure you used to measure the A-Arm heights/levels. Not because there's anything wrong with your post - maybe I just need more coffee. However, my concern about your procedure would be whether or not the car/tires/jacks/whatever have freedom to slide laterally as you lower the car onto them to get the measurement. If not, then bind will mean the car isn't sitting as it truly would on its tires after being rolled around. That could be affecting things. Second, you need to make this measurement with the sway bar unhooked. Maybe you are. Just making sure. If it's still connected, then it could preload the suspension.

 

Do you have the same height differance at the rear suspension?

 

@AZSP33D @MatthewMiller @JoBy Thanks for your replies. To clarify, i wasn't measuring any distances. I simply noticed there was space between the passenger A-arm and block i was using to support the lower A-arm before i jacked car up. There was no space between driver A-arm and block before i jacked car up. Not knowing any different or better, i was simply asking if these differences are ok.

Having read your replies, in all humility I must add, I don't know what I'm doing. That's why I'm going to have our dealership who's experienced and friendly with C4's set alignment.

 

In the end, for a given car it's most important to have equal diagonal corner weights: take the individual weights at each contact patch and sum LF+RR and RF+LR. We want those equal so the car has equal handling balance (understeer or oversteer) when turning either direction. If you only turn one direction, like circle track cars, you can make them unequal on purpose (that's what "wedge" is).

That said, it's a concern if the frame height at various reference points isn't the same on the left and right sides. There's room for some inaccuracy there: A C4 should be better in this regard than earlier full-frame cars, but significantly less uniform than later generations. I'll post below the Factory Service Manual's page on measuring the "straightness" of the unibody. The absolute measurements from the data points to ground are not important, since they obviously depend on tire sizes, spring and shock combos, etc. However, in the ideal world each left datum should be identical to its right counterpart, and their relative heights should match what's on the page (e.g. get Datum A 75mm lower than Datum F and then the rest in between should have relative height conforming to the book). And again, the C4 is not a "perfect world." I don't know how much variance is considered okay before you cross over into it being considered a bent frame. Also, again, you can't measure these things with the car jacked or having been set back down without a way to unload the lateral bind. My guess is that this is what happened to you. Actually, using folded plastic trash bags under each wheel is a good way to free up that bind without rolling the car. You also really need to measure this is without the sway bar connected.

Assuming the frame is straight, and assuming you have the correct and matching suspension parts on each side, then the distances to ground or whatever should be uniform. If they aren't, then they should at least be low pretty uniformly along one whole side of the car. If that's the case with the bar not connected, then it's time to start looking at one or both springs to see if they are damaged, their end and center bushings are in good shape, and the control arm bushings are intact. Any modern gas shock has some spring rate to it, but not usually a lot. Still, check that the shocks are in good shape.