car rocks?

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We have a 1989 mercury tracer (mazda 323-- but with hatchback mexican body and ford logo) with 71,000 miles. We put a lot of work into it last November: new rear springs, new shocks all the way around, alignment (front end is still solid), wheel bearings all the way around, brake lines, front calipers, rear wheel cylinders, parking brake cables were alternating rusted through in 2 places and rusted together in 2 other places (replaced entirely). I have only recently started driving it very much myself, so I cannot tell you whether this was always the case, or recently began, or began after the work in November. My sister tells me it began a month ago (well after the work, and recently). I drove it 900 miles immediately before and after the work in November, and don't specifically remember anything like this. When driving on concrete --not asphalt-- especially with the coarser lines scored into the pavement, at say 50-80mph, the car will start a harmonic oscillation. It will rock side to side in a consistent and cyclical fashion, that's irritating, and at worst, detracts from driver control. It is not wind-related. Is this just life with a small, light weight car at high way speeds? The shocks are new. There's no discernible front end play. What can cause this? Is this at all in line with tire balance? (a wheel weight fell off?) Or... it's not impossible and there's reason to fear it... if one of the nuts on one of the front shocks that holds the macpherson strut together at the top has some lash or has backed off, would it manifest in this way? Other thoughts? -Bernard
 
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no idea on the actual question, but a curiosity for you on the car itself. My cousin had one of those for many years. hers had peculiarity about the doors. if you didn't hold the outside handle up when you closed it, the door wouldn't stay locked. (if you just closed it normally,the door would unlock itself) She bought it new, and it did that from day 1. does yours exhibit a similar behavior? or have you heard of that before?
 

berninicaco3

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Question is about the problematic handling on the highway, and what to start looking at... or if this is just normal for subcompacts? Before this car, I drove a full size station wagon, and before that, a trailblazer, so I don't have much experience with little cars. Yes. Think about it-- it's to keep you from locking yourself out! We figured it out pretty quickly. I locked all the doors, shut all of them, and returned to find both front doors (only) unlocked. You have to shut it, and lock it from the outside: which means of course that you must have your key in your hand, and can't lock it in the car without really trying. Clever, really. Hadn't thought about just holding the handle open: 6 in one hand, half a dozen in the other between that and just locking it from the outside with the key.
 
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Originally Posted By: Roadkingnc
Its the tread design on the tires following the rain grooves in the concrete.
+1!
 
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Yeah, the reason it's happening on grooved concrete is because the tread grooves on your tires are interacting with the grooving in the concrete. The amplitude of this effect (how much it does it) will be highly variable depending on a lot of things. Vehicle weight is one, and the individual tire is another. The width and spacing of the tread grooves may be just right on your particular tires such that it has more of an effect than it would with a different set of tires perhaps. Our Acura MDX is over 5,000 pounds loaded with the family and cargo, and it will move back and forth on some grooved concrete. I've found that speed will have an effect as well. As you said, it seems to be a harmonic motion, and a number of variables have to line up to make it feel severe.
 
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ditto: tire tread pattern and grooves. my toyota echo started doing this on a 10 mile stretch of road after I put new tires on the car. it's a little ensettling, and I figure that the grooves are accelerating the wear on the tires. as far as door locks - I had a VW Fox with the same thing - you had to hold the door release in as you closed the door.
 
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Saw a camry from the 80s that did that door lock thing. Was a Japanese fad. My mercedes 240d had a mechanical interlock that kept one from pushing down on the driver's door lock, at all, while the door was open. When closed, you could use the key, or reach in through the open window and do it. smile
 

berninicaco3

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ah! thanks for the answer. As it happens, we DID put on new tires in november. Michelin weatherwise II for what it's worth. We did the tires in Iowa, drove to Baltimore for a vacation and did all the other work in a friend's shop there, and drove back, never noticing the phenomenon in 1800 miles: but we had 500# of additional cargo (or more!) for a trip like that, vs. now, when we're just commuting empty-trunked.
 

berninicaco3

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and here I was, wondering if a wheel weight could have fallen off, or if something horrible happened to the front struts.
 
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