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Forgive me if this already has a thread for it, I haven't been on the site for quite a while to say the least!
Does anyone have any alignment specs for lowered Third Gens? Mine wanders like crazy with minimal steering inputs and wants to set, and then reset in a corner. Unnerving at speed to say the least. The car has an Eibach Pro-Kit, Wonder Bar, and Adjustable Panhard Bar and is riding on 17s. And, my dumbass put poly-graphite bushings in the front lower control arms a few years back (big mistake). It was aligned after all of these to what I can only assume are the factory specs in the computer. Due to life and with the wandering problems, it's outings have been limited the past 2 seasons. Now that we are into spring I'm ready to dust it off and get it out into the sunlight. My buddy now has a shop with an alignment rack, so I plan on taking it to him and was wondering if anyone could point me in the right direction so he has something better to go by.
I knew someone had to have covered it, and I actually did come across that chart, but in a random search and wasn't quite sure the relevance to my situation. After reading the whole thread, this seems to be the information I was looking for. Thanks for setting me straight. (I didn't have a lot of time to dig due to a hungry infant on my lap, so I figured I'd just throw it out there!)
What you may be experiencing is Bump Steer, Bump Steer is when your wheels steer themselves without input from the steering wheel. The undesirable steering is caused by bumps in the road interacting with improper length or angle of your suspension and steering linkages. Most car builders design their cars so that the effects of bump steer are minimal. It mostly occurs in lowered cars or in those fitted with aftermarket control arms or camber kits. In short, any modifications that reposition the 3 main linkages (tie rod, upper, and lower wishbone) from intersecting at the IC cause bump steer. This can cause toe-in or toe-outdepending upon the placement of the steering rack. Ideally the angle of the lower control arms and the tie rods should match, you can correct this by using a Bump steer kit.
Some light reading and links below to Bump steer kits, you can source the parts individually to save a little money but make sure you do your research. Another note wheel inside diameter becomes an issue with a Bump steer kit, 16's I don't think you can, 17's are questionable but 18's and 19's you should be good to go. Bump Steer Explained: What It Is, Causes & How to Eliminate It! | Low Offset (low-offset.com) Bump Steer (vacmotorsports.com) UMI 3060-1 82-92 F-Body, 78-88 G-Body Bump Steer Kit, Heavy Duty (speedwaymotors.com) Firebird Bump-Steer Kit, 1982-1992 (ecklers.com)
Thank you for the info. After doing a little digging and finding the alignment print-out from my last alignment, I see that the specs are quite far from where they should be according to the above chart. They've got it set at a half a degree positive camber and virtually no toe, though the caster is right on the money. Back when I had it done it hadn't even dawned on me to consider the fact of the new parts and setup changing the geometry of everything, I just saw green numbers on the print-out and went on my merry way. After a little bit of schooling myself, I know better now and think this is where I'll start. I'm lucky that my buddy now has a shop with a rack for me to "borrow" on weekends!
The factory 3rd gen alignment specs call out for positive camber.
it was a result of people in the 1980s complaining about weird steering effects at low speeds.
So a shop will just automatically use those specs even though factory settings are trash.
Good street alignment:
-0.5 degrees camber+5.0 castor0.1 degree toe in, about 1/8in ish
you can use Zero toe if your steering system is fairly new
But honestly, it sounds like your steering needs to be rebuilt.
bump steer when lowered isn't that bad on 3rd gens.(I've tested bump with a gauge a LOT of times)
You should replace all steering links, box, and a solid astro shaft.
I Wouldn't bother with an alignment until you have redone the steering system.
I have a video on the link replacement, and another on the box.
0.1 degree toe in, about 1/8in ish
you can use Zero toe if your steering system is fairly new
Does your car buck in tight turns with toe in?
I've always used a smidge toe out and car drove nice. Just tried 1/16" toe in and now car bucks baaaaad in tight turns. Just wondering if yours does too and you're putting up with it or if you actually don't use any toe in with your car.
Are you referring to the odd steering feeling at full lock and low speeds?
if so, that's because the GM engineers fuc*ed up the ackerman angles.
There is unfortunately no way to fix that.
Toe in will worsen the effects at low speeds.
But Toe in will also make freeway travel way nicer.
For what it is worth, I don’t think bump steer is as bad of an issue as people make it out to be on these cars. Sure the ackerman angles don’t help, and scrub isn’t ideal either. I put 1” extended ball joints on my lowered IROC, and that combined with the anti-ackerman and no bump steer kit should make my car undrivable. It isn’t though. In fact, it drives incredibly straight, and takes large bumps just fine. The small amount of suspension travel on a lowered car helps minimize this.
I guess my point is don’t worry about achieving perfection, when the car can handle just fine without making things perfect (ie achieving zero bump through whole range of travel). Just give the car what it wants!
My lowered setup is -1.5 degrees of camber on each side, -4.5 degrees of caster both sides, with zero toe, or just a touch of toe out. The wheels will want to toe in under any suspension compression the way I have things set up.
My bump steer was pretty bad but then again most dont drive threw the turns hard or fast enough to really notice. I have had 1/2" extended ball joints for the last few years and just added a UMI bump steer kit last summer and has made a huge difference
1/2in extended Ball-joints will give you about 1/4in of bump steer with a stock setup.(yikes!)
I managed to get my bump to 0.002in at 2in of travel and 0.006in at max drop or compression.
Makes the car far nicer to drive around without the car wandering all over the road.
But just lowering a 3rd gen won't give you unliveable bump steer like many claim.
