Rubrignitz

As of about 15 minutes ago I now have a fully adjustable rear suspension setup. I've installed an adjustable BMR upper control arm and also have BMR adjustable lower control arms with relocation brackets. I have a UMI Performance adjustable panhard bar as well.

I have NO idea how to adjust all this now that it's on the car. I had adjusted my LCA's from the stock length of 18.5'' down to 18'' to correct the pinion angle but now that I have the adjustable upper I'm not sure if I should move them back out to stock length and control the pinion angle solely with the upper CA adjustment. I know the lower CA length adjusts driveline/track length and with my one-piece driveshaft I'm sure that it's critical to have the correct driveline proportions.

Can anyone let me know where I should begin?

SlideWRX

The adjustable panhard bar is largely there to correct side to side variation. Measure how far in the wheel is from the body lip on each side. Half the difference is how far the panhard needs to be adjusted.

You don't have to control pinion with just the uppers or lowers. I'd actually split the difference, and that should keep the track near stock. If you are drag racing, moving the rear axle forward would have a slight improvement on traction; don't know if it's enough to show up in timeslips though. On the other end of that, if we increase the length of the upper control arm the ride should get a wee bit better.

Rubrignitz

That is exactly what I did last night. I had the adjustable lower CA's shortened from the (stock) length of 18 1/2'' down to 18'' in order to correct the pinion angle with the stock non-adjustable upper.

Now that I have an adjustable upper, I lengthened the lower CA's back out to 18 3/8'' (near stock length) and shortened the adjustable upper CA to get my pinion back to -2/3 degrees. Took a long test drive last night and everything seems to be adjusted perfectly now. I knew what to do with the panhard as far as correcting axle alignment, just not about the upper/lower CA's.

I guess it's not rocket science but I was wondering where to begin with it!

2007CalSpec

I know this is an old thread but I had a question about the lower control arms. If you adjust the lower control arms to be shorter, does that pull the wheels closer to the front of the wheel wells? I ask because my tires stick out past the fender lip very slightly and if I got adj. LCA's then I'm afraid it might cause the tires to rub the front edge of the fender. I'm just trying to decide if I should get adj. LCA's or UCA. I know LCA's would be easier to adjust then a UCA but I don't want adj. LCA's if they'll cause tire rub.

Rubrignitz

I don't think you'll have tire rub issues, but yes, adjusting the lower LCA's affects wheelbase. So to answer you question, you will be able to fine tune your wheel-clearance a bit with adjustable LCA's.

I don't think you will need it but I'd never run 295/20's so I can't say for sure.

2007CalSpec

Maybe I should get both adj. LCA's and adj. UCA just to be safe. That way I can adjust the LCA's first and see if they rub the tires. If they do then I'll back them out and only use the UCA for the pinion adjustments. I really don't want to use the UCA for the adjustments 'cause it looks like a pain to get to them; especially when I only have two jack stands and I know the car has to be level.

Rubrignitz

I'm going on record to say that the ONLY way to get your pinion angle spot-on, especially with a one-piece driveshaft is with an adjustable UCA.

You may be able to get it close enough to not cause trouble with just adjustable LCA's but an adjustable UCA is invaluable.

Get them both if you can afford it. The adjustability is nice, though I set and forget it's nice to know I can adjust for future mods etc.

Norm Peterson

You may very well NEED both the LCAs and a UCA to be adjustable, if you're trying for a specific axle location with respect to the wheelwells/sheetmetal AND trying to set a particular pinion angle. Depending on how fussy you are about this, you may be in for some "back and forth" adjusting between the lowers and the upper.

Adjusting the length of either the LCAs or the UCA will affect wheelbase.

LCA adjustment can also be used to get the axle square in the chassis. That also means that you can knock an axle that's already square to the chassis out of alignment if you aren't careful.


Norm