Here's the deal; driving down the freeway (Concrete with the linear parallel grooves) my GT wants to jog back and forth. Not in any huge amount, just enough that I can feel the motion and it's a little disconcerting. However, this doesn't occur on the blacktop portions of the freeway, only on the concrete sections. My car is lowered and poly'd up; could this explain why it seems to track the grooves in the highway? I don't notice it in my Infinity QX, Dodge Dakota or my GMC Canyon. I might also add that my whole suspension is new, save for the rear hubs. They were bought from a forum member in used condition. I did notice that one of them seemed to have just a little play in it, but I am planning on replacing them anyway. Any tips or advice is greatly appreciated.

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Peace!!

B2 OUT!!
86GT 3.4LProject

[This message has been edited by BAM-BAM (edited 03-15-2012).]

Did you replace the cradle bushings at all? I replaced mine with solid aluminum ones and I can tell a huge difference over the 25 year old rubber ones.

it's normal for your car to do that on grouved pavement some tires amplify the feeling wich is most likely why you don't feel it in your other vehicles.. my 2004 4runner does the same thing you are explaining but my 2005 matrix xrs doesn't.. hope this helps

A couple of things come to mind. First, I’m assuming that you had the alignment done after replacing all of the suspension part and/or when you had it lowered. If not, do so. Next, Fiero’s will “bump steer” because the rear toe will change as the rear wheels move up and down. It’s a pretty bad design flaw that comes from the rear tie rods having a different angle than the control arms. With that said, I struggle to believe that the road you described is bad enough for this to be the problem. Lastly, given all of the vehicles you described, the Fiero is likely going to have the lowest profile tires (I’m guessing here). The lower the tire profile the less sidewall and the less sidewall the less the tire can flex side to side. Because of this low profile tires will “track” with groves in the road surface more the higher profile tires and/or tires designed for comfort. As to the difference with the road surface, different tire compounds react differently to different types of surfaces. It could also be the groves in the concrete but the basic effect is the same. Somewhere in all of this is probably the reason (maybe a mix?). About a year ago I changed tires on my 87GT and there are now a couple of sections of local freeway where the car tracks much more than other sections. The tires I put on were sticker then the ones that came off so I’m pretty sure that’s it.

Now, with all of that said, let’s not rule out the possibility that there is something loose in the suspension somewhere (don’t forget the front end, it could be a factor) so my advice is to get the car up on a lift that is a “drive up ramp” type where you can lift the car but the car is still sitting on all fours tires (like an alignment ramp). Once there wiggle and shake everything both front and rear then do the same thing with all four tires off the ground and the suspension hanging. This is something that should be done before an alignment is done anyway.

I had a car that did this, and it unexpectedly went away when I put new (different) tires on it... Could it just be the shape of the treads?

[This message has been edited by lukemo (edited 03-15-2012).]

Definitely tire related; I take My '85 2M6 down 101 usually going home and the car tracks perfect....But sometimes I drive 280 and the car squirms substantially.....280 has grooved concrete, while 101 is asphalt.

If you noticed any looseness in the hubs, then that's likely part of it. My car does the same thing (tramlining) but it was significantly improved after replacing a bad hub recently. The rear hubs shouldn't have any movement at all when you try to wobble them.

BTW, I was not happy with Timken for multiple reasons... if you order their hub I hope you get better luck than I had. My biggest complaint is that the seal didn't even fit the hub it was packaged with (duh). But it's installed now, and hopefully will last longer than the PO's aftermarket hub it's replacing.

How's your tire pressure?

I just had a wandering like that on my 88 that was slowly getting worse. It came out to be a loose axle nut. Anything loose in the rear of these cars will cause this. Check that all is tight. Since you messed up with all is probably something got forgotten.

Worn out rear struts caused that feeling in my 86 2m4.
A squirrely feeling.

Sorry, I was under the weather for the past couple of days. Yes, I replaced all of the bushings and yes I had an alignment done. I do have lower profile tires with my 17's and I suspect this to be the issue. It's not really bad, it just keeps me thinking while I am driving and that in itself is probably a good thing. I appreciate all of the feedback, thank you all so much.

------------------
Peace!!

B2 OUT!!
86GT 3.4LProject

With the profil that you would have to have in order to have it lowered, and have 17's on it, I am a little surprised you hadnt noticed this behavior before. This is very likely just the tires following the grooves and contours of the road. Still be sure to give the suspension a good once over, but I'd bet a beer or two that its the lack of flex in the tire, which causes a difference in amount of tire contacting the road on grooves, and therefore a difference in friction, ergo wandering as this occurs.