[matjow]

And what do they do? What is the benefit of an adjustable one over one that is not adjustable?

BMI Fabrications sells some high performance ones. But I don't even know what they do.

http://www.bmrfabrication.com/SSR.htm

 

[rick418cars]

an adjustable set would allow you to change
your pinion angle, sometimes needed
when drag racing for off the line tuning
of high horsepower vehicles

 

[Ken Thurm]

When you lower your truck you need to correct your pinion angle so your drive shaft is in phase with your differential. These allow you to do this.

 

[matjow]

Thanks!

Do they give you any better handling?

Is it really worth spending the money to replace perfectly good factory parts for these "High Performance" ones?

 

[rick418cars]

my opinion is no, i'm a fan of oem style bushings,
poly bushings can squeek and tranfer un wanted
vibrations, the stock control arms are plenty
beefy enough ...................