my car is ''twitchy''

[ga.spyder]

I did a front end rebuild this winter,everything went well.I noticed afterward that the car is very sensitive on uneven roads,changing lanes on crowned roads or raised paint stripes.The car has always done this to an extent,which I attributed to the wide tires I run.I took a long trip this weekend ,and went through a lot of const. zones and rough roads.You have to stay on top of your driving,or at times it wants to throw you into another lane.It has become a safety issue.My question is,what could cause this?I feel it has to do with the alignment.Do I need more camber or caster? I remember the alignment guy saying he had it in spec,but it might need more shims on drivers side.I am pretty sure they went back the same as I took them off,but...? Are the shims available to buy ? Everthing is tight in the suspension...I double checked torque settings,etc..this afternoon.Any feedback or advise is ,as always,appreciated.
Craig

[majicwrench]

Wide tires will make a car "twitchy". Hopefully the alignment is to specs, but excesive toe out can also make a car "twitchy". If you have options, the more caster you have, the more the car tries to drive itself straight ahead.
Hope everything is tight and done right...
Keith

[So Cal Mark]

the car should not change lanes! If the alignment was done to spec, why would it need more shims? I'd bet either the toe is WAY off, or the rear end locating bars have worn out bushings. The other possibility is that the control arm bushings have failed. We've been seeing bushings made in India that fail almost immediately. I'd get that thing raised up and look it over before disaster strikes

[rlux4]

Naah, I think the aerodynamics got messed up when you pulled the bumpers in.
Ron

[pope]

Hows your steering idler arm?

[ga.spyder]

All good suggestions(except Ron who is jealous of my tucked bumpers!).I may have overstated a bit,it isnt bad enough to switch lanes.It gives you a feel that it might,but I have experimented with my hands off the wheel and the car will move some on uneven surfaces.I put it up on ramps and checked the front end and all looks good.Everything was torqued to spec,and bushings,ball joints,links,etc...look great.The car has always been twitchy a bit,but seems worse now.I will talk to alignment guy Mon re. the shims,but toe is correct,and the cam/cast was in the spec range.
Mark, you may have hit on something with the rear trailing arms.The mechanic who owned the shop where I did the rebuild said it looked like both long arms had been bent and straightened! The pass. side has a visible dent in it(like someone had a jack under it).I didnt think this could affect handling,and was just a locator for the rear end assembly.Could this make the car unsable? If so,new ones will be installed ASAP.
Pope,I will check the idler arm and box today.I didnt think about it when I was checking yesterday.
Craig

[racydave]

Craig, some little things that can contribute to this also are loose front wheel bearings, or toe-out. The major culprit may be in the rear assuming your alignment specialist was good. If your steering gear was over tightened, it might give it a weird feeling also. Sometimes its a combo of things? Do your brakes occasionally pull too?

[So Cal Mark]

when you bend the rear arms, you effectively shorten them. If one is shorter than the other the rear end is no longer aligned in the car. As an aside, those rear bars will break at the spot they are bent if there is any kink in them

[ga.spyder]

I think the bearings are fine,they were replaced during the rebuild.I used all top quality parts.I did have a brake pull but that was addressed and it doesnt pull at all now.That makes sense re. the rear arms.I looked at them carefully today,and both have issues.The pass. side has a crimp in it.The drivers side looks almost twisted a little.Bayless has new ones pretty cheap so even if it isnt causing the cars 'nervousness',I think I should replace them. The idler arm looks fine,but I really dont know what to look for.It isnt visibly bent.
Craig

[pope]

Did he do an alignment based on 4 wheels and not the front alone, I hope. Idler arm should have oil in it, and not dry. It would stop twitching but not drifting of the wheels. I think Marks idea is good, but dont know if it would get worse like you say, I would think it would be consistantly bad, unless one is ready to give up the dust. Hope you find the culprit.

Maybe there is a teddy bear caught in the steering mechanism.

[ga.spyder]

He did not align with the rears,he said he didnt have the equipment.My mechanic friend was concerned about the rear,he was the one who spotted the bent trailing arm.I did top off the idler a couple weeks ago.Is it possible that it feels worse because there isnt as much give in the suspension with all the new parts? The bushings and tie rods I removed were worn to almost non-existence.I am ordering the new trailing arms tomorrow.I have gotten where I dont like to order on the net,because of stuff not being in stock!
Craig

[kilrwail]

Craig - Not to take anything away from all of these excellent suggestions, but was the car twitchy before the front end was rebuilt? Secondly, what tire pressure do you run in your larger tIres? You might need a higher pressure, to avoid "squirm". In my 185's, I run 29 psi, which works well.

[ga.spyder]

Peter,I have experimented with the air pressures,and it doesnt have much effect.The car was twitchy before the front end rebuild,but I attributed that to bad bushings,etc.. Now that all is new ,I need to find the cause and eliminate it. I know some of it is the wide tires,but I am suspect of the rear arms which are definitely damaged,albeit slightly.
Craig

[joelbert2k]

I know this is somewhat off the mark but I remember when the Datsun 240z first came to America it developed a terrible rep for wandering and following the grooves in the pavement. The fix turned out to be quite simply. They added a small, less than an inch I think, chin spoiler and that took care of it. The Spiders have never had this problem that I know of so I doubt this is your problem, just reminiscing.

Joel

[ga.spyder]

I have ordered the rear trailing arms from Bayless.Hope to get them ,and install by the weekend. My mechanic feels that the rear end is 'pushing' the car a bit and thinks that the rear arms should help.He is of the opinion that my wider tires and wheel offset are going to also make the car sensitive to uneven surface.If so,I will live with it! I am hoping the rear arms will help ,sure can't hurt.Both of them do look to be damaged somewhat.
Craig