Front shimmy on touchdown

[ljmachguru]

I have a slight front end shimmy when my tires touch back down after launch. Front end seems pretty tight. No wheel slack. I do not have any travel limiters on the front end, So the travel is going to the bottom. I can feel the slight shake when it touches and it feels like its slowing me down just slightly when it does the shimmy. Any suggestions on how to eliminate this problem are greatly appreciated.

[supernova]

Get some video posted and let use take a look.

[Craig W.]

Stock steering or rack?

[wikd69]

my 2 cents...

Does the shimmy / vibration smooth out after the car settles back down ? If so, then you may be experiencing an issue with alignment changes at full extension of your front suspension. Mine was doing the same thing until I changed the alignment up front and added limiters in my front A-arms which only allow the front end to lift so far at launch (~ 3"). This keeps the front wheels in the 'sweet spot' for castor/camber/toe-in and has the side benefit of helping keep the front end down at launch.

Of course, I'm still a rookie at this and may be completely out to lunch on the topic :) There may be other issues or causes for your shimmy that I'm clueless about.

[John_Heard]

Probably lack of caster and/or bump steer issues as noted above.

[ljmachguru]

Front suspension is stock only with exception of shocks, standard s-10 manual worm box. I only have a microsecond of shimmy when it just starts to touch . As soon as any load gets on the front it stops and drives like a caddy.Will try to get a decent video. I am concerned about the front shimmy even its only for a half a second. If it will help I will install limiters so it stops before it hits bump bottom (unloads completely). Thanks for the replys, I knew you guys would offer a professional response.

[ytnova]

My bet would be lack of caster or bumpsteer issues as well, how much caster is in it? I have also seen cars do this from just play in all of the steering components also. When you check each item individually, they are pretty tight, but when you add all the play in them together there is just enough slop to cause the wobble. This is one of the other benifits of going to a rack, there are less moving/wearable items in the steering system.

[John_Heard]

Good point, I tend to forget about stuff like idler arms... Grab the tire and shake it side to side while you've got someone underneath watching all the joints. Might be something worn out.

[mcdn81olds]

We have an '85 firebird & 75 nova that had the same problem. We added a "shimmie" shock that helped tremendously. It's kinda 4 wheel drive technology, but works.

[Dave Morgan]

There are a lot of good points made here:
BUMPSTEER- Toe-change during vertical wheel travel. This is pretty easy to fix, normally requiring a spacer between the outer tire rod ball joint and the steering arm, or by changing the height of the steering arm in that location (remember to cold-form it with a hammer, don’t heat it.)
CASTER- Caster chatter is caused when the caster angle equals the Steering Axis Inclination (known as SAI). This is the same angle as caster, but viewed from the front of the car. This is why some guys run into this problem as they add caster to the front end.
WORN PARTS- The idler arm and pitman arm are high-wear components and if they do wear, the easiest indicator is that the center link may be at an angle when the car is at ride height. John’s recommendation of raising the frontend and jiggling (that’s a scientific term) the tires is another good indication.

[79 Camaro]

Probably lack of caster and/or bump steer issues as noted above.

I agree, I have the same issue. Crazy bumpster!

[Craig W.]

My car had a little shimmy with the stock steering setup that would sometimes slightly upset the car after the tires touched down. After I went to the rack but before replacing the steering arms, the bump steer was terrible and on the verge of dangerous. I couldn't get the tie rod end in the right spot with the stock steering arms. After I changed to the TRZ arms, I was able to get the bump steer down to a minimum.