Scottie-GNZ Posted May 16, 2002 Share Posted May 16, 2002 I read Al's issue with great interest and now would like to throw mine out for dissection. I have always had a little shake in the front wheels at about 55-65mph only. It was so minor, I never paid much attention to it. Now it has gotten considerably worse and I need to do something about it. Keep in mind that the problem kicks in sharply at 55 and goes away just as sharply at 65 with no evidence of a problem outside that range. The wheels are Swastikas and the tires are 205/60-15, recently mounted and balanced. The previous tires had the very same minor shake, so I rule out the tire switch. Hi-po springs, Illuminas, recent (w/in 2 yrs) ball joints and outer tie-rod ends, alignment just a coule of weeks ago and that produce no change in the minor shake. Parked the car for 2 weeks to do bodywork and started getting the violent shake immediately after that. I also rule out the fenders . Obviously the minor and major shakes are the same problem but what brought on the sudden change? Checked and retightend wheel bearings but no effect. Quote Link to comment Share on other sites More sharing options...
Dragonfly Posted May 16, 2002 Share Posted May 16, 2002 Why is that things like that always seem to be in the speed range that you have to drive in when there is a cop around Just my suspesions here but is it possible that you have a small amount of play in your steering rack that allows you to feel an amplified resonance. There is a chance that your rims, rotor, or hub could have a certain rpm range that causes them to go into a harmonic resonance creating your vibration and as soon as you get past that rpm range (wheel rpm) it goes away. A good way to test this is to see if it starts at exactly 65 when slowing down then ends at 55, if it starts and stops at the exact same rpm range in both directions that could be your source. Dragonfly Quote Link to comment Share on other sites More sharing options...
Tim240z Posted May 16, 2002 Share Posted May 16, 2002 Scottie, It definitely sounds like a dynamic inbalance of the front wheels. You may have thrown a wheel weight, or the tires have gottten very slightly out of round from sitting (unlikely). Have the wheels rebalanced. Make sure that they DON'T pull the weights off the wheels before they check them on the balancer. This way you will know how out of balance they are/were. If you can find a shop that can do it, have the wheels balanced on the car. This is accurate to +- 1 gram, whereas the regular offcar dynamic/static balacing is only accurate to +- 5 grams. Tim Quote Link to comment Share on other sites More sharing options...
Mike C Posted May 16, 2002 Share Posted May 16, 2002 I thought the dots were heavy and light spots? Any reasonable tire will be mostly round. Try greasing your steering rack and see if it gets better packed full of grease. I would check inner tie rods. I would say wrong offset wheel, but the Nissan ones should be OK. I've seen lots of shimmy problems on my own cars with positive offset wheels. Quote Link to comment Share on other sites More sharing options...
jeromio Posted May 17, 2002 Share Posted May 17, 2002 I've had this problem on 3 different cars and each time it turned out to be tire/wheel problems. Either the wheel was out of balance, or the tire had a blorp on it or some combination. Quote Link to comment Share on other sites More sharing options...
Tim240z Posted May 17, 2002 Share Posted May 17, 2002 One thing to keep in mind also is that many/most manufacturers have colored dots on the sidewall of the tires (usually 2). The colors' designation varies, but one always represents a manufacturing 'high spot' (read heavy spot), and the other dot coincides with placement of the tire relative to the valve. Most tire shops pay absolutely NO attention to these dots, and probably will think that you are talking crap when you mention it. If they do, go somewhere else. Although in many cases ignoring these mounting indicator dots will not create much noticable difference, in many cases it will and you will find yourself chasing balacing problems forever, especially if the balance issues occur at higher speeds...ie 45mph and higher. Tim Quote Link to comment Share on other sites More sharing options...
Guest Aaron Posted May 17, 2002 Share Posted May 17, 2002 In my previous ZX I had similar shaking problems. At first, it would shake at 50-60 MPH, as time went on, it migrated to 35-60MPH. The problem was the inner tie-rod on the rack. Quote Link to comment Share on other sites More sharing options...
Scottie-GNZ Posted May 17, 2002 Author Share Posted May 17, 2002 Unfortunately, I also suspect the inner tie rods and that is not something I want to tackle right now. How difficult a job is that? Quote Link to comment Share on other sites More sharing options...
Guest Aaron Posted May 17, 2002 Share Posted May 17, 2002 Don't know, I sold the car before I fixed it because the dealer kept getting the wrong part. However, on the '89 Escort I had, it only took a few minutes with the right tool. On it, you removed the outer end from the spindle, then took it off of the rod. Count how many revolutions you turn it so that when you put it back on the alignment will be close enough to get you to an alignment shop. The inner tie rod simply unscrewed with a homeade tool that was essentially a 18" deep socket. Took about 20 minutes from jacking and dropping. Obviously, you have to get the think realigned, and you may want to replace both of them just to be safe. Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted May 17, 2002 Share Posted May 17, 2002 Keep in mind there is a chance that everything in your suspension is fine and you have a resonance problem. Ever see the videos of the Tacoma Narrow Bridge? If a mechanical system is stimulated with vibration of the correct frequency, it can resonate just like a guitar string. I would assume your front end has been modified to stiffen everything and to remove all of rubber pieces with derlin or aluminum. Datsun added all that rubber for a reason. Thus if I were you I would check the wheel balance like everyone suggests. I would also make certain none of your tires are out of round. Know this one from personal experience. I would also think a bad alignment could contribute to the problem. Once you are sure you have no front end problems, then you may need to do things to try and dampen the vibration or change it's frequency. I am not sure how you would go about this. Anything you do, like switching to a different type of tires or shocks, could affect the problem. Quote Link to comment Share on other sites More sharing options...
Tim240z Posted May 17, 2002 Share Posted May 17, 2002 Jim, While I agree with you somewhat in principle, I don't think, from what Scottie has described, you acessment is correct. Generally the only variable in wheel alignment that will cause a vibration would be a high caster angle and then that would show itself as an increasing vibration as speed increases, not a speed segment as described. Also, a drivetrain, or rear wheel imbalance for that matter, would not tend to show up as a steering wheel vibration, but rather a whole car vibration that will generally be felt in the seat (or seat of your pants). If the front tires are out of round, that may create a steering wheel vibration, but will also make the front of the car appear as if it is hopping. Bad shocks will cause a scalloping of the tires and will cause bad tire/road noise, but generally no vibration. Just my 2c worth. Tim Quote Link to comment Share on other sites More sharing options...
jeromio Posted May 18, 2002 Share Posted May 18, 2002 Perhaps no one mentioned this because it is obvious, but I for one found out the hard way that one of the tierod ends is reverse threaded. And now I can't remember which one, although I think it was the passenger side. Quote Link to comment Share on other sites More sharing options...
Modern Motorsports Ltd Posted May 18, 2002 Share Posted May 18, 2002 Scotty, I'd recommend having your wheels checked to ensure they're straight. I've had exactly what you describe and it was a very slightly bent wheel. Bent wheels can still balance easily, to be diagnosed they have to LOOK at the wheel when spinning and 99% just put the hood down and let it spin.....I had a slight bend in one rim years ago on an old set and once it was fixed no vibes.......I can't explain how it got stronger, perhaps it shook a weight? As well I've found new tires (especially R compounds) require a rebalance quite often within a few hundred miles/break in....they seem to settle in on the rims or something to that effect. HTH Quote Link to comment Share on other sites More sharing options...
Cody 82 ZXT Posted May 18, 2002 Share Posted May 18, 2002 I've had several cars with slight shimmy for years. This latest one my 82zxt is the car that I've had the longest and started to notice how when I went to different shops the quality was different even thought it was done on the same basic machine. Last summer I replace everything but, the rack and sloved most of my proublems. When I went to have the rims rebalanced just to make sure, the guy put the stick on weights and the typical hammer on. This was the best it has ever been. I instist on the techs doing it this way now. I can't remember what type of balance it is called but, the guys in the shop will know. Also you may have the same condition that my car has right now and thats just that the rack is simply worn out. No matter how much you do it will never be perfect until it gets replaced. As for how hard the inner tie rods are to put on. It very easy if I can do it you can. Later Quote Link to comment Share on other sites More sharing options...
auxilary Posted May 19, 2002 Share Posted May 19, 2002 checked your steering rack bushings? If they're shot, this could be a good reason to change them out to PU ones. MSA sells them for 11 bucks I think. Just a suggestion Quote Link to comment Share on other sites More sharing options...
Tim240z Posted June 5, 2002 Share Posted June 5, 2002 Scottie, Did you ever track down the prob? Tim Quote Link to comment Share on other sites More sharing options...
Scottie-GNZ Posted June 5, 2002 Author Share Posted June 5, 2002 Yes I did. Sorry. Turns out my front tires had flat spots even though I do not recall a panic stop that significant. Much better after some different tires but it is still not perfect. I also discovered from 240Z Turbo that my car has a 280Z rack with 240Z bushings which probably explains why my steering tightens up when I bolt down the clamps . I might still have worn inner tie rods, but I will wait until I get some 280Z bushings. Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted June 6, 2002 Share Posted June 6, 2002 The way your car launches, are you sure the flat spots aren't a result of your front tires not being able to spin as fast as the car accelerates? Quote Link to comment Share on other sites More sharing options...
pparaska Posted June 6, 2002 Share Posted June 6, 2002 Jim, those flat spots are from Scottie hangin' the hoops for half way down the track and them having to "catch up" all the sudden when the hit the pavement but aren't turning yet . Kind of like what happens to an airplane's tires when it first touches down . Scottie, I've heard of a bunch of weird things causing this. I think Dragonfly's post needs to be paid attention to. It seems my years of reading about this problem on Z's points to play or slop in many places that can be the cause of this vibration. No tire/wheel is perfectly balanced or perfectly round /concentric with the bolt circle or hub center. Your rack bushing situation would be one of the first places to look. Also, follow the tighten, back off, tighten procedure for the wheel bearings in the Z shop manual. I've heard of both of these as being a problem with vibration in the front of the Z. Quote Link to comment Share on other sites More sharing options...
opie Posted June 6, 2002 Share Posted June 6, 2002 I worked in a tire store for 3 yrs and what Scottie described was always a rotating mass issue. It's balance, roundness or side runout on the front. Scottie, if the Z rack is similar in design to the ZX, it's is not difficult at all. Opie. 69 Conv. LeMans 70 Conv. VW 71 240Z 73 Superbug couple of drivers also. Quote Link to comment Share on other sites More sharing options...
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