I currently have the standard Spohn PB on the car. It also has the standard Spohn LCA's w/ reloc brackets. I'm about to put some Eibach Pro-Kit springs on it.

Is it necessary that I purchase an adj one to "re-align" the center?

I thought it used to say that on the Spohn website, but now it no longer says it. Did I miss something?

 

One quick short answer....YES.

 

Do you have to.....NO. Is it a good idea.....YES. The lateral positioning of your rear is going to be off by a smidgeon. There is more reasons to get one tho. Stiffer and lighter than stock.......If you care about handling, I have heard they make quite a diff. I am going to make my own.

 

depends on how much you lower..

 

I lowered mine and the stock bar work fine. The rear was almost perfect centered.

 

It all depends. I would suggest to go ahead and put the springs in without one, then take a few measurements and go from there.

 

It does vary on how much you lower the car, and it does vary from car to car depending on production tolerances. I have seen lowered cars with the rear wheels offset by as little as 1\4" to over 3\4". Now some people may not consider 1\4" a lot....but in racing circles that is not acceptable.

I used to be of the opinion that an adjustable bar is not really necessary....but I have since changed my opinion after seeing the difference that a properly centered rear end can make to a car.

Proper corner weighting is something that few people do for Amateur Racing. Extremely rare for the street. But it does make a difference in the cars setup. The rear end on my car ( Eyeballed with adj Panhard ) was out by 5mm to the left. By getting the rear DEAD centered with the car we optimised the crossweight in the car to within 1.5% of being perfect. With a lighter driver ( or if I lost 30 lbs ) we would have been within 1% of perfect crossweights. You can't get much better than that.... without compromising other areas.

There is a difference between just being just OK....and being perfect. That difference is often what wins races.

 

Chickenman,
How do you properly center your rear? I would assume you want the suspension loaded. Where should I be taking my measurements from? or does it even matter?

 

Easiest way ( For a street car ) is to hang a plumber's bob string ( Or a big nut and string ) from the edge of the 1\4 panel down through the centerline of the wheel, then take a measurement from the string to the edge of the rim. More than accurate enough for a street car ( and most race cars )....assuming of course that your car hasn't been hit in the rear at some time in the past.

Edit: Spelling

 

That doesn't work unless you're completely level. I was watching a friend do this and he was all confused with the results. Needless to say our "level" shop floor was designed to drain water .
The best way to center the rear is to eye ball it into range and then do the rest by corner weights. I find this hard for the average joe without $4000 scales so my ideas; Go and get a professional alignment with the front and rear....use the plumb bob but don't go down to the center of the rim, if you went to the top of the tire there would be less error.... anybody else have any good ways?

 

After lowering my car front and rear, mine was off to the left close to 3/4" of an inch. With my car sitting in my garage where it is level I took my 4 ft. level and stood it on end against the tire and car and measured the gap. Then I adjusted my panhard bar to center the rearend under the car again. Mine was truly noticable after lowering the car. I got the Edelbrock adjustable panhard bar, nice unit that is easily adjustable on the car while it is on the ground.

 

Yes...forgot to add...floor must be level. But it must be level to use electronic scales as well.

You cannot center the rear end with corner weights. It just doesn't work that way and it's not that simple. A properly setup car has crossweight percentages equal to the left and right hand total weight percentages. That means that you can have left and right corner weights that are different ( front or rear ) . It is EXTREMELY rare to get each rear ( or front ) corner weight equal. Maybe on an F1 car or a Champ car.......virtually impossible on a street car.

Check the ground with a level. Run a plumbers bob down from the 1\4 panel through the center of the rim and then take the measurement to the EDGE of the rim ( that would be the upper edge by the string ) as I stated. The edge of the rim is a lot more accirate than the edge of the tires. Tire sidewalls can have runout and bulges. Rims usually do not. If they do then you have bigger problems.