Tim240z Posted May 14, 2002 Share Posted May 14, 2002 Al, It is not an alignment problem (just to validate, I was an alignment tech for several years). It is either runout on the rotors (most likely), or possibly the ball joints are shot). Jack up the front of the car and grab the wheel at 12 and 6 (clock) and tug back and forward. If there's play, snug up or replace the bearings. Then grab the wheel at 10 and 4 (clock and tug back and forward. If there's play it is the ball joint. Also, is the vibration through the steering wheel or the seat/car? Tim BTW, if there is no suspension play, get the alignment checked anyway. That should be checked at least every 8-10,000 mile or less. Quote Link to comment Share on other sites More sharing options...
alsil Posted May 14, 2002 Author Share Posted May 14, 2002 Thanks, I'll check that. Sounds like it could be either to me. I think the wheel bearing is more likely, but we'll see. Thanks AL Quote Link to comment Share on other sites More sharing options...
auxilary Posted May 14, 2002 Share Posted May 14, 2002 Originally posted by alsil:Thanks, I'll check that. Sounds like it could be either to me. I think the wheel bearing is more likely, but we'll see. Thanks AL I think I have some left over inner and outer races for the bearings, I didn't use them (they're new) since mine were in good shape. Don't have any spare bearings though, let me know if you need them. otherwise you can get new bearings for 7/each at kragen for inner, and 6/each for outer Quote Link to comment Share on other sites More sharing options...
Tim240z Posted May 14, 2002 Share Posted May 14, 2002 Al, If you are going to replace the bearings, remember, don't overtighten them. Many people believe that the correct way to set bearing preload is to tighten them down and then back off the nut until the hub spins freely. At this point the damage is done. The correct way is to keep tightening until there is no play (lateral) in the bearings. Run them as loose as you can without having any play. Also, remember to check them again after a few miles of driving, incase they have bedded in a bit and some play has developed. If you don't need to replace them, just ignore all this Tim Quote Link to comment Share on other sites More sharing options...
alsil Posted May 15, 2002 Author Share Posted May 15, 2002 The verdict: Ball Joints: both good Wheel bearings: Driver's side was loose. pulled the rotor and hub, repacked, checked the bearing, repacked, bolted back on. Made sure it was not loose.....but not too tight..... Drove out on the freeway....hit the brakes...no change. why do I always get the weird stuff?? Something I noticed: I have Mike's 300zx rotor/4Runner caliper setup with the 300zx hub. I noticed that the spacer between the rotor and the hub was not perfectly centered. Now I have no idea why it wouldn't be, but I don't know if that would cause this issue. Shouldn't it vibrate the front end ALL the time...? I dunno but I think I'm gonna pull it off when I replace the bearings (better safe than sorry) and see what's up..didn't have time tonight, also have to drive it tomorrow.... Thanks guys! AL Quote Link to comment Share on other sites More sharing options...
Tim240z Posted May 15, 2002 Share Posted May 15, 2002 Al, Get yourself a dial indicator with a magnetic base and check for runout on the rotors, I'm certain that has to be it. Maybe they have warped slightly. Tim Quote Link to comment Share on other sites More sharing options...
alsil Posted May 15, 2002 Author Share Posted May 15, 2002 My Z has started shaking when I hit the brakes over 40mph. I thought maybe something was loose, but I checked all the bolts and they are OK. I am wondering what could be causing this. It all of the sudden started happening, so it's got me worried. It kind of looks like the front end it toed out a bit, but not sure if that's the cause. Anyone have any ideas? It doesn't shake at all unless I am hitting the brakes. Also, the harder I hit the brakes the more it shakes. If anyone has any ideas, let me know. thanks! Al Quote Link to comment Share on other sites More sharing options...
Modern Motorsports Ltd Posted May 15, 2002 Share Posted May 15, 2002 Al, does it shimmy at slow speed braking? ie. just rolling up to lights/stopsign? Warped rotors is first detected at slow/mild braking IME, once it's at higher speeds then it's further along IME. Your caliper pistons moving freely I assume? Quite rare but a pebble can get caught b/t pad and rotor and cause some odd action....seen that. Good luck! Quote Link to comment Share on other sites More sharing options...
alsil Posted May 15, 2002 Author Share Posted May 15, 2002 No, at low speed it's smooth. Absolutely no vibrtations at low speed. Just above 40. Checked the rotors/calipers/tension rods/control arms/strut/etc.....nothing's loose..... any alignment guys out there? Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted May 15, 2002 Share Posted May 15, 2002 Same thing happened to my Z. The steering wheel would vibrate back and forth when I would brake from speed. Got worse the faster I went and the harder I braked. In my case it was warped/worn rotors. Check the rotor run out. Any good shop manual will tell you how. If the run out is excessive you might be able to get them turned. At the time new rotors from MSA were only $35 each, so that is the route I went. Quote Link to comment Share on other sites More sharing options...
alsil Posted May 15, 2002 Author Share Posted May 15, 2002 My brakes are pretty new (3000 miles on brand new rotors)....I'll check though.....thanks... AL Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted May 15, 2002 Share Posted May 15, 2002 Check the condition of the wheel bearings. My car (not a Datsun/Nissan) had exactly the same symptoms you describe and it turned out I had a bad race on an outer wheel bearing. Quote Link to comment Share on other sites More sharing options...
Mike C Posted May 15, 2002 Share Posted May 15, 2002 I'd also try and shim/adjust that front caliper so it is centered on the rotor. Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted May 15, 2002 Share Posted May 15, 2002 You've got us all interested now! If you had the stock unvented rotor then I would add that it is entirely possible to overheat and warp the rotors with one "spirited" driving session. Since you have the 300 ZX rotors (which I assume are vented), then I would hope that is is much harder to do. At least that is the whole point of going to that set up, better heat dissipation. Still think you need to check the rotor run out before you do anything else. And since you didn't specifically mention it, make certain the rest of your front end parts are solid (tie rod ends, bushings, TC rods, steering rack mounts). The spacer being off center would imply a wheel balance problem like you mention. A vibration during braking might be caused if the spacer was not perfectly flat (thus the wheel is not truely perpendicular to the spindle axis), but since I assume this problem was not present from day 1 it is probably something else. Quote Link to comment Share on other sites More sharing options...
alsil Posted May 15, 2002 Author Share Posted May 15, 2002 Well then I guess I'm taking a trip down to the machine shop this weekend...... The caliper is centered correctly, I checkd that last night. New rotors are $74 a piece....hope these aren't too bad. Wish I didn't have to drive the Z until then....might be maing it worse. At least the bearing is OK. Thanks Guys! AL Quote Link to comment Share on other sites More sharing options...
Tim240z Posted May 19, 2002 Share Posted May 19, 2002 Al, Did you find the problem...curious as to the final determination. Tim Quote Link to comment Share on other sites More sharing options...
alsil Posted May 19, 2002 Author Share Posted May 19, 2002 yep rotors slightly warped. Thanks for the input guys, I think my power booster was over boosted and really clamping down on my rotors. I have disconnected it, and the brakes feel much better now. I don't mind it being a bit heavier, in fact, it's not much heavier than my wife's car and she's got power. Thanks! Al Quote Link to comment Share on other sites More sharing options...
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