Have a buddy that wants help (known as you do it and I'll watch) lowering the rear on an '89 coupe.Don't mind doing it for him but he insists on an alignment afterwards.I'm suggesting to him that it isn't necessary. Will be dropping the car approx 2",rear only. What are everyones opinions?

 

Mine would be to have it aligned. Lowering the car that much will definately change the alignment and tires are too expensive to wear badly just because it wasn't aligned. JMHO.

 

Yup, align it.

 

Not only that but, lowering it and not having it aligned will also change the contact patch during spirited driving.

 

 

what about lowering the front and having it aligned? I noticed tonight as I removed the front suspension that GM placed small shims(various lengths) at the bolts of the upper a-arms. After lowering, should some be removed/added?

 

Lowering the rear will affect the caster on the front wheel alignment. I would suggest an alignment after lowering. I know there have been many posts about this topic since I am considering the same.

Good luck,
Dino

 

I droped mine about 1.5 all theway around and was borderline getting the caster within the "recommended limits"... but it is a definate to get it aligned...

MO

 

Those shims set the caster and camber. So, yes some should be added/removed.

 

I'm assuming GM has an assortment of shims and any reputable wheel shop would be able to align? Or would the dealer be able to align the car after lowered even though its not stock?

 

Any shop or auto parts store should have shims. In fact, doing alignments at home really isn't that hard. It does take some time to make sure you have a nice level spot (4 spots to be exact) and a decent camber/caster tool does make things easier (investment of approx $200).

Those things and little patience and you can probably do a better job on your own car than any alignment shop will. I've come to not trust any shop that won't just setup to the specs I want. They always have more "experience with these things" or "only work to factory specs". What a bunch of : I know my car and what works for it.

Didn't mean to but it really isn't that hard to do. There are a number of articles on how, I'll see if I can dig up the one I used.

 

please do

 

What specs should I use for 1991 C4 after lowering 1" all 4 corners?
Are the advanced street specs on this side good for it?

 

Same here. I also do my own alignments. If anyone wants-I can email the way I do mine.

Steven

 

Nutz4c4,

I received your PM, for some reason my email did not go thru. So I will post here.

I have post this a few times. On my last alignment I did not use the mica turn tables.

This is the way I do my alignments. (On MY C-4)

Please note I am not a mechanic but I have been doing my own alignments for many years.

Stuff you need:

6' level
2 tape measures
camber/caster gauge
abs shingles or masonry shims
toe plates(cut the bottom of each plate to clear the bulge of the tire)
2 pieces of 4x4 wood cut to about 8" each and index w/1/2" increments.
laser pointer
4 12"x12" pieces of mica

First take the 6' level and find a level place in your garage or driveway,
use the abs shingles or the masonry shims if you have to.

You will have to set the camber/caster first. On the front add or remove the shims on the upper control arm. The rear Loosen the Bolt closest to the rear on the strut rod bar and turn the bolt to adjust (its slotted). Please note that this bar should be tighten to 185ft pounds. (My car has an aftermarket bar with 2 ends with jam nuts)

After you think you have it set drive the around the block to settle the suspension and check with the camber/caster gauge. To check the caster turn the wheel out approx 15 degrees and set the gauge to zero. Then turn the wheel 15 degrees in and read the gauge. Most gauges have the sweep angle built in so it is easy to do.

Now for the toe. Do the rear first. Now I know there are many ways to do this but I think this way might be the easiest. Take the 12" mica and use them as turn tables (2 pieces with oil in the middle) roll the car over the mica. Take the toe plates and lay them on each tire. Simply measure the front and rear of each plate. Now take the 4x4 index wood and lay them in the middle of each front tire/wheel. As you adjust your toe (by loosening the jam nut on the tie rod) take the laser and put it against the toe plate and aim to the 4x4 wood and try to get each side close (as we will do this also for the front). I have read here that other Forum Members simply aim at the ground (I will try this for my next alignment)

When you think you have it then do the same for the front and again aim the laser now to the back tire/wheel using the same 4x4s (try to get this close as you want the rear tires to track straight (thrust angle).

Drive the car again and check all measurements. This will take approx 2 hours or more! I have found that bouncing the car does not settle the springs/shocks. Maybe for a street car w soft springs/shocks-not a Vette or race car.

Hope this info is helpful take your time and you can do this yourself!

Dave Farmer also has a tech on this subject.

Steven