Front End Alignment

[rossiz]

after replacing the front steering rack bushings and upgrading the suspension i noticed the steering wheel was a few degrees off and figured it was time to check alignment. the z is amazingly simple to align, with the only adjustment necessary on the end of the tie rods. there may be other ways to get the toe angle correct (some folks use a rod or wire to measure the tires inside-inside at different locations) but i've always used a simple old-school setup that just requires some string and a rod.

in case anyone is looking to do this, here's the process i used:

• get a rod or piece of wood that is a bit longer than the width of your tire spacing (outside to outside)
  
• attach it to a wall or some heavy object - concrete blocks will work (you need to get some tension on the strings)
  
• mount it at the wheel centerline height, or a little lower if required to clear hub caps or center caps stick out
  
• park the car square to and centered on your rod/wood bar, about 15' or so away (i was lucky to have a centerline in the concrete pattern)
  
• tie the string to the back wheel at a lug nut or the wheel itself, inboard of the plane of the tire, such that the string runs over/touches the tire sidewall when pulled forward
  
• pull the string forward, loop it around the rod/bar and pull it taught, adjusting it in small increments to get it to just graze the sides of the front tire
  
• do the same on both sides of the car
  
• measure width of string at tires, then match dimension at the rod/bar
  
• set the steering wheel to the center position, check to see if one or both wheels are out of alignment
  
• undo the lock-nuts on the tie rod adjuster rods, turn the adjusters in or out as required to line up the wheel w/the string
  
• lock it all back up and take a test drive - it may take a few shots to get it just right, depending on how much slop there is in your system
  

set up rod, line up the car, pull the strings:

get strings lined up with the tire sidewalls one side at a time, checking dimensions at the wheels and at the rod do ensure strings are parallel

measure how far out you are and in which direction

as you crank the adjuster keep an eye on the tire - you can watch it move as you turn the wrench and dial it in

all done in about an hour (i was lucky - no frozen threads!) and now she tracks nice and straight :classic:

[olzed]

I use this method around all four wheels. A good check for rear misalignment as well.

[Captain Obvious]

Very nice. I'm going to have to think about the geometry of this method.

Hey, did you re-establish baseline on your control arm bushings first?

[rossiz]

control arm bushings - front ones didn't do much at all when i loosened the bolts, they weren't stuck at all. rear ones are still as is, i need to get a big enough six point socket...

[Mikes Z car]

rossiz,

Thanks for taking the time to post details and drawings of the layout for testing the toe, I need to check that on my car, haven't been able to understand the write ups others have done on this but yours makes sense to me (good drawings help!). I have been known to miss the obvious though.

Captain,

How does one establish baseline on the control arm bushings? Does that verify if they are soft enough they should be replaced? (edit later- to see if they are stuck apparently). My car doesn't have directional control the way my '71 Z did, either the rack bushings or the control arm bushings must need attention. The tie rod ends are good I believe from videoing them as I yanked the steering wheel back and forth.

Edited June 9, 2014 by Mikes Z car

[rossiz]

Mike: you can check the rack bushings for play by opening the hood, rolling down the drivers window, then lean in w/your right hand and move the steering wheel back and forth while watching the rack (just follow the steering column down, you'll see it under the engine between the wheels).

my rack bushings had given up and i could see the rack moving side-to-side as well as vertically when the wheel was moved. the new bushings keep the rack dead still.

you can also check for play at the wheels by jacking up the front of the car until the wheels are off the ground, then grab the tire and try to wiggle it side-to-side, as if steering the car. you will be able to easily move the steering wheel with your hand on the tire, but you shouldn't feel loose play in the system.

[Captain Obvious]

One establishes baseline for the rubber bushings by loosening up the center lock bolt while the suspension is under load and allowing the rubber to relax to thier natural un-stressed position. Loosen the lock bolts, "jounce" the suspension a couple times, maybe push down just a little (unless you've got someone to sit in the driver's seat for you), and then tighten the lock bolts. This is all because of the way the rubber bushings work, and especially important if you've done significant suspension work or lowered your car.

You don't do this to assure they're not stuck... You have to assure they're not stuck in order to do this. (Does that make sense?) If the bushings are rusted into place, they will not normalize. The inner sleeve must be free enough to rotate to it's relaxed position and it won't do that if it's stuck rusted in place.

What you're trying to prevent is having the rubber portion of the bushings under any rotational stress while the car is under "neutral" load sitting still flat and level. When the car is neutral, you want the bushings neutral. This is the theory behind the requirement in the FSM that you load the suspension before tightening up the suspension points. This requirement only applies to the control arm pivot points though. T/C rods and sway bars don't care. Tighten them hanging or loaded, no difference.

I whipped up a couple sketches of the control arm bushings that show the theory of how they work. Here's a front bushing:

Here's a rear inner bushing:

And here's a rear outer:

[John Coffey]

Good post ^.

Sway bars also should be tightened at the end links with the car on the ground and in a neutral position after doing the control arm bushings above. You do not want to introduce preload in the sway bar (its a spring) when tightening the end links.

[Captain Obvious]

Thanks John, I'm not a suspension guy at all so bear with me a little. Here's my thoughts on the sway bar.

The sway bar is a spring, but it's used in torsion. Torsion which is developed only when one wheel is higher than the other. If both wheels are at the same altitude, there's no torsion. As long as both wheels are hanging at the same altitude or both wheels are loaded to the same degree, it's the same thing to the sway bar. Neutral. No preload.

Said a different way, if you attach both end links with the wheels hanging and then put the car on the ground, the ENTIRE bar (both ends, AND the center portion... Everything) will simply rotate in the two frame mount bushings as the suspension is compressed. But there will be no torsion at any time.

Am I missing something?

[John Coffey]

You are assuming that both wheels droop the same amount. They don't, for various reasons. You also assume that every car sits level side to side while on the ground and loaded. They don't, for various reasons. You are also assuming the end links are equal length, the control arms/bushings are in the same position vertically, ...I can go on...

One little quibble... coil springs and torsion bars work the same. The spring material is twisted as the spring is moved through its range of travel. Coil springs are just torsion bars wrapped in a circle.

[bacarl]

The sway bar will add spring rate too ("wheel rate") if the frame mount bushings are torqued while the suspension is hanging. The frame mounts are particularly important to torque while the suspension is loaded.

Great posts.

[grannyknot]

I'm constantly impressed with the knowledge of this forum.

Gents, by using the above method I should be able to fix a steering wheel that is slightly askew, right?

My toe in is set at 3/16ths on the front wheels and the car tracks well but my steering wheel is not centered, it's off by a smidge. I have tried correcting it at the steering wheel spindle but one spline either way is too much.

I know it's not a big deal but on a long drive a crooked steering wheel just gets under my skin.

Thanks,

Chris

Edited June 11, 2014 by grannyknot