Car jerks like crazy over uneven surfaces..??

[135 Boom]

So when I go over any uneven surface my car jerks left or right like crazy. It has steeda lowering springs and camber plates other than that it is stock. What could be the problem? Its so bad I had to let off when I was owning a STI today and now my ego hurts.

 

[Lstruck03]

some cars do this after being lowered. Usually, a bump steer kit will solve the issue

 

[JrSVT]

What bushings do you have in the IRS....you say other than Steeda lowering springs and C/C plates it's stock. Chances are that if you haven't replaced the 11-12 yr old bushings in the IRS they could be causing this to happen.



Jr.

 

[UncleSAm]

Check the rear spindle nuts, get a bump steer kit or/ steeda 2x ball joints,

The ball joints alone salved my issue

 

[135 Boom]

Ok I will get the bumpstops and see if that works. Thanks everyone

 

[TBCobra]

Are all four tires the same size? If not, having wider tires in the back and smaller in the front can cause your car to pull left and right.

 

[snakeraper11b]

So when I go over any uneven surface my car jerks left or right like crazy. It has steeda lowering springs and camber plates other than that it is stock. What could be the problem? Its so bad I had to let off when I was owning a STI today and now my ego hurts.

Did you just add the camber plates and springs? If so, lowering the car causes a change in the bump steer to toe in rather than toe out under compression like ford designed. Also, if you installed camber caster plates on top of the springs, more caster will result in further exacerbation of the roll oversteer sypmtom, which is high unstable. You will need an adjustable tie rod end bump steer kit to fix that problem. 99% sure that is your issue.

 

[weaselp1]

Did you just add the camber plates and springs? If so, lowering the car causes a change in the bump steer to toe in rather than toe out under compression like ford designed. Also, if you installed camber caster plates on top of the springs, more caster will result in further exacerbation of the roll oversteer sypmtom, which is high unstable. You will need an adjustable tie rod end bump steer kit to fix that problem. 99% sure that is your issue.

I had a similar issue to you OP, so last year I put in FTBR rear IRS bushing kit and rear bumpsteer kit. That fixed the rear. Then I noticed my front was all over the place when going over bumps with just HR race and MM CC plates. I just put in new Global west front control arm bushings, Steeda X2 balljoints and a MM bumpsteer kit and all is fixed. The front end is solid now. IF you do get the front bumpsteer kit, make sure you get the bumpsteer kit properly setup. A simple front end alignment will not work; you need to get the front bumpsteered correctly. Good luck!

 

[ac427cobra]

You have received some great advice so far and I would also jack up the car and feel every wheel for play in all directions. If you have any play, you need to investigate and correct.

You also may have bumpsteer issues from the car being lowered.

Good luck and keep us all posted.

 

[135 Boom]

Thanks for the reply's. I have never messed with installing a bump steer kit, could I do it then get it aligned? Or should I have it installed? The car came with the plates and springs installed. The guy who owned it was 68 and had a shop do all his work, so I am sure they aligned it afterwards.

 

[weaselp1]

A front bumpsteer kit is basically adjustable tie rod ends. You can install those yourself in less than 30 minutes; but after the installation you need to take it to a shop that knows how to set the bumpsteer and align it properly; you can do it your self, but you have to have the correct tools to do so. Here are some good videos on set bumpsteer. http://fulltiltboogieracing.com/informational_videos.htm

I also have seen other shops winch down the suspension on a come along on an alignment rack to set bumpsteer; I would call your tuner and ask if he can set bumpsteer; chances are if he does not bumpsteer cars he will know of someone that does; whatever you do, do not take it to a Firestone or some chain shop unless they know what they are doing. Bumpsteer is set one time and it needs to be done correctly.

 

[135 Boom]

Ok, so as I was looking at the car tonight I noticed the camber plates were not even on both sides. The only reason I bring it up, is because I had a lowered mustang before and it jerked a little. The car cannot go over a bumpy surface without hitting both lanes at 15 mph. So I was looking at the camber plates and one looks like it had moved quite a bit from where it was originally mounted. The other has not moved at all, and is fully seated to the rear. Could this be a factor also? I will try and get pics to upload.

 

[135 Boom]

 

[snakeraper11b]

That is going to result in a few degrees less caster in the passenger side. That would cause some amount of instability, but I think it would come in the way of the vehicle not wanting to hold a line and constantly pulling, not so much a jerk over uneven terrain. You have the rust marks, reset it to the marks, take it for a test drive. If the symptoms persist, address the bump steer. If it solves your issue, then you're obviously good to go. I don't think it will clear you up 100% though.

 

[135 Boom]

Moved it back, seems to have almost cut the instability in half.

 

[ac427cobra]

Moved it back, seems to have almost cut the instability in half.

Get a new alignment. If that does not cure the problem, you're most likely going to have to bumpsteer the suspension.

 

[135 Boom]

answered already, thanks everyone.

 

[spdfrkaby]

I know you said you got your answer already but just in case someone else runs across this with a similar situation, I 'd throw my piece in to. I had pretty bad pulling issues left/right with just H&R Springs installed. With the Steeda X2 and bumpsteer kit it made a huge improvement and rides straight over bumps and doesn't jerk me to the left/right on uneven roads. I don't have a caster camber plate installed. Just an informational.

 

[weaselp1]

OP, did you ever figure out the issue?