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Discussion Starter #1
how does one adjust the camber in the rear when there is only one cam bolt toward the front of the vehicle and the rear lower control arm bolt seems fixed?
 

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The cam in the front will change camber, just keep in mind that you will have to reset the toe as well. Increasing negative camber will create toe out, reducing it will create toe in.
 

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Discussion Starter #4
Thanks, it makes sense pushing out the forward facing side of the lower control arm will cause toe out.
I also understand how adjusting the toe will push the rear of the tire out and effectively act as a rearward facing lower control arm cam bolt.
What I don't understand is how does a seemingly fixed rearward facing lower control arm bolt accomodate lateral movement?
 

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03 Z06 said:
What I don't understand is how does a seemingly fixed rearward facing lower control arm bolt accomodate lateral movement?
The rear bolt acts as a pivot point so it really doesn't have to move much at all. If you think about it, how much does the front have to move? 1/8" up front = big change in camber. ;)
 

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Discussion Starter #6
Up front I had to move the cam bolts about 1/8 inch on both cams to get about 1/2 degree additional negative camber.

In this case do I even need to loosen the "pivot" point bolt?
Seems like the bushing takes the additional rotation.
 

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03 Z06 said:
In this case do I even need to loosen the "pivot" point bolt?
Seems like the bushing takes the additional rotation.
I'd loosen it to make sure it doesn't bind at all. Better safe than sorry.
 

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03 Z06 said:
ok, I will try it.
BTW, have you done a rear alignment yourself?
Yes, when I installed the Hardbar fixed camber plates. I used the "David Farmer" method that's been posted here and on the other site. I also did some trigonometry calculations to confirm the accuracy on the camber settings. For thrust angle, I tied string to two jackstands, lined the string up against the rear wheels, then measured the distance to the front spindles. For toe, I picked up a set of Longacre toe plates that work great.
 

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I did all my alignments myself for the 2004 season. Yes, the rear camber bolt does change camber. If you look closely at the a-arm you will see that the front arm goes most straight out so moving the camber bolt moves the bottom of the spindle out increasing negative camber. As mentioned, this has a huge impact on toe (will go to toe out as negative camber is increased - note front is opposite due to position of tie rod in front vice in back of spindle).

Adjusting toe has very little impact on camber as the tie rod is almost centered on the relative height of the spindle.

Adjust camber first, then toe.

To check camber, the car must be on a perfectly flat piece of ground or leveled (which is what I do as my garage is inches from flat)

When playing with toe you must keep individual as well as aggregate toe in mind. I use the David Farmer "gun sight" method of checking thrust angle. Easy and actually pretty accurate. I check total toe with toe plates and tape measures - accurate to about 1/32". Then I put a six foot level on the outside of the wheel looking forward and sight down it and do the same on the opposite side. It is very apparent if the thrust angle is not centered.

The front is much harder as the camber bolt impacts camber a lot and caster a little and the rear caster concentric bolt impacts caster a lot and camber a little. Very iterative process for me on the front. :cheers:
 

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Discussion Starter #11
thanks for all the info.
I will work on the LR tomorrow morning, the car goes to Summit Point on Monday and Tuesday, so I would like to get it done before I leave, I only need about another .4 negative camber.

Yes, I leveled the car in my garage with 2#12s and then shimmed them as necessary to get 4 corners level. I did the last 1/4" of shimming with two 1/8" composite tiles, acting as turn plates when they are put shiney sides facing eachother.

I will look up the David Farmer method and try to compare my results between the two methods.

BTW, what do you think of my laser string method?
 

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Discussion Starter #12
I just researched the David Farmer method.
I like the idea of checking track with a long straight edge from rear to front. However good luck finding such a long and straight one. The deviation in the 2X4 could be enough to make you believe you wrong or right!

I don't agree with using the distance behind and in front of the tires for toe. Since that will tell you if the tires are parallel, but will not force them to be toed correctly with respect to the centerline. Think of an extreme example where the LF and RF are perfectly toed 45 degrees to the right with respect to the center line of the vehicel. The distances in front and behind the front wheels would be perfectly equal but the car would not defintely not be toed correctly.
 

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The laser toe method is fine, but a pain. And you still have the question as to how do you align each of the side lasers with the car centerline (e.g. the two lasers have to be perfectly parallel and they have to be parallel to the car's centerline)? That is really hard to do accurately.

I agree that David's 2x4 method shouldn't use 2x4s. I use a six foot aluminum level and it is perfectly straight.

As for the thrust angle, I tried to explain above that you really can get it very close using the Farmer method. I can make a 1/32" change in toe and tell from the Farmer method that toe changed.

I make this assumption: the front wheels are square with the frame and use them as my "target". Maybe not perfect, but very close.

I think when you put a six or eight foot level on your back tires and look down the level to the front and use the outside edge of the front wheels as your "target" you will find that you really can even out the thrust angle so you get the right amount of toe on each side.

As an example, say I want 1/4" toe in for the rear, 1/8" both sides. I use toe plates and set rear toe to 1/4" toe in. Question then is, what is the thrust angle. I then use the level to sight down the front. Lets say LR points inside the outer edge of the front wheel and the RR points outside. I then lengthen the RR tie rod (more toe in on the RR) and shorten the LR tie rod (less toe in on the LR) the same amount. Then I sight it again. Repeat as necessary until the two levels intersect the front wheel at the same place (which for my 17x10 fronts is almost exactly on the outer edge with the rear toe in I run). :cheers:
 

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Discussion Starter #14
ok, I finished last night and ran distances behind and in front of both axles. I register no toe on the front and about 1/16" total toe out in the rear. When I use the laser to measure toe on each wheel I get zero up front, expected, and almost zero in the rear, close enough.

I align the laser equidistant with the hub in front and in the rear, and a perfectly centered steering wheel.
I made the assumption that the distance from hub to hub on the front is axle is equal to the distance between hub to hub on the rear axle.
Double checking with a tape ruler behind and in front for total toe confirms I can do that on the C5.

In all these measurements, placing tape measure on uneven ground, reading level bubble perfectly centered, calculating center of vehicle perfectly, etc. there are errors that creep in. If you were to add up all the slop I'm guessing that we could be off by at least a 1/16" if not more in any direction. Hence, I'm not so confident any one method provides a high amount of accuracy. Precision yes, repeatability, but absolute doubtful.

I agree my method does not take center line into account, hence thrust is in question. I don't have a long enough straight edge to check what my thrust departure is, if any.
 
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