After installing a set of Vorschlag front camber plates, I went to Sneed's Speed Shop for an alignment. All went well in front but we couldn't get enough adjustment out of the rear lower control arms to properly set the rear camber and it would appear virtually impossible to get to the rear trailing arm toe adjustment without taking off the outer aero rocker panels and underbelly trays. (What kind of masochist designed this fiasco? Certainly not a track junkie!) My first inclination is to purchase both upper and lower aftermarket control arms to get both camber and toe adjustment. Anyone got an alternate solution? Recommendations for brand of control arms? (almost akin to asking favorite brand of oil or whether you like blondes, brunettes or redheads!)

 

It's true- The GP's panels cover the toe adjustment bolts.

 

Only the small panel, hiding the bolts, needs to come off. The belly pan does not need to come off. With the small panel off there is enough room to get to the bolts for adjustment. The adjustment at the trailing arm bolts is not easy because it is a little trial and error because you loosen the bolts, move/slide, the arm, measure, tighten the bolts, measure, and find that it shifted a little during tightening.
The first time the alignment shop did my GP it took him over an hour to align the rear to my specs. The second and third time the tech was much faster.

On my 03 MCS I used H-Sport rear Lower Control Arms. I did not replace the upper rear control arms. The H-Sports were quiet and strong. I had a hard crash into the rear wheel and the arm bent but did not break.

 

We saw no small panel that would give us a straight shot at the trailing arm bolts. Are you referring to the small panel on the bottom rear of the aero rocker panel? We tried going up thru there but it required so much contortion and no room to get a wrench, much less see what we were doing. If you can find a picture or diagram, it would really be appreciated.

 

Well, I went the EZ route. Thanks to Way, who had in stock and immediately shipped a set of 13810 H-Sport upper and lower rear control arms, this was the best (not least expensive) solution. Installation went well and, after an alignment from Sneeds, in addition to the 2 degrees neg. up front, I have 1.5 neg. in the rear. The only other possibility would've been to drill 3 ea. holes through the bottom of the aero panel exactly below the 3 adjustment bolts so that they could be accessed by a long extension and 18mm socket.

 

Is adding the toe using the control arms not going to add stress onto the trailing arm bushing? I know the adjustment is so minimal it should not matter correct?

 

Trackrat,
Glad you got your GP all aligned to your specs.
I guess I should be happy my alignment guy got the rear toe adjusted using the trailing arm bolts and did not drill any holes in the panels. He said it was a pain. I am not sure what tools he used and maybe I do not want to know. I saw an alignment guy adjusting my car's rear camber at the lower control arm with channel locks so now take the proper size 12-point bow end wrench for the tech to use.

Professor,
I have never heard of anyone having problems with bushings when using upper and lower control arms. I think you are right that the adjustment is so small that it has no affect on the bushing.

 

If your worried about the trailing arm bushing you could install the Powerflex trailing arm bushing inserts. These are great to minimize toe change mid corner too.

 

It is a huge pain. I watched my shop do it and you have to contort and reach into the space under the rocker and aero panel to get your tool in there and then do you thing. It did take about 30 mins to adjust just one side!

 

I've been following this thread with great interest and was hoping someone could shed some light on toe and camber? What is the benefit of adjusting the toe and camber? Is this just for track use? What is toe and what is camber? Sorry for the naive question, but I'm just really interested onthe benefits/detriments to changing these settings. Thanks for the help guys.

 

For the 2006 GP; the front toe, rear toe, and rear camber are adjustable. The front camber and front caster are not adjustable.

Camber is the adjustment for the tilt of the wheel. When looking from the front or rear of the car, camber is how the top of the wheel/tire tilts into or away from the car. Negative camber / \ is when the top of the tire tilts towards the car. Positive camber \ / is when the top of the tire tilts away from the car. You can probably see negative camber on the rear tires of your car. Negative camber is good for better handling. With negative camber; when you are driving straight the tire rides slightly on the inside edge of the tire but as you turn the car the car/tire leans and the tire then rides flatter on the road thus providing better traction when turning (more tire contact patch on the road). The con is that the inside edge of the tire wears faster if you mainly drive straight and do not turn hard.

Thus for better handling people add negative camber to the front tires by installing camber plates. With front adjustable camber plates, I run -2.2 degrees in the front and -1.5 degrees in the rear (using stock adjustable rear lower control arms).

Toe is how the wheel/tire points in or out when looking down on the car from above. Like looking at your feet. Toe-in / \ is when the front of the tires are pointing in compared to rear of the tires (like walking pigeon toe). Toe-out \ / is when the front of the tires are pointing out when compared to the rear. Most alignment machines use a positive measurement for toe-in and a negative measurement for toe-out. Total toe is the summation of the left and right toe Most vehicle manufactures spec a little toe-in for two reason. 1) Because the toe can change as the vehicle lifts a little at highway speeds, so a little toe-in at rest should mean about zero toe at highway speed. 2) A little toe-in creates more stable straight driving. The con of toe is that it causes more tire wear because toe makes the tire scrub across the ground because the tire is not pointing straight.

I run slight toe-out in the front for quicker turn-in (steering response) but that makes the car less stable in a straight line and wears the tire a little faster. I run zero toe in the rear for best tire wear.

Caster is how the wheel tilts forward or backwards, compared to the suspension, when looking at the wheel from the side of the car. The amount of caster is designed into the car and is not adjustable without aftermarket parts. Positive caster improves straight line tracking.

Another normal alignment measurement is Steer Ahead. I am not exactly sure what is meant by Steer Ahead. I suspect it is how well the steering wheel is pointed when going straight. i.e., Is the steering wheel straight when going straight? The Toe adjustment will change the steering wheel angle if they adjust one side more than the other. Steer Ahead should be as close to zero as possible.

Another normal alignment measurement Thrust Angle. Thrust Angle is the direction the rear wheels are pointing in relation to the center line of the car. The thrust angle should be zero.

 

Good recap Quickmni. There is magic to be found when someone that knows their way around an alignment rack and the result of their work on a vehicle's dynamics. A great alignment can literally change a vehicle from being mediocre to amazing.

 

Quikmni, I wanted to thank you for such a thorough writeup. I really appreciate you taking the time to inform a newbie on how different setups will affect the dynamics of the car. Now all I need to do is start trying different things and seeing what happens. Thanks again!!