Phantom Posted January 6, 2004 Share Posted January 6, 2004 OK - I've got the infamous front end vibration. It occurs on my car starting about 65 and holds pretty solid up to 80 and then starts diminishing a bit. Tires have been dynamically balanced. Lug nuts were torqued with the car in the air (16x7 lug centric Center Line Wheels). New Urethane bushings on the radius rods. I haven't had the alignment checked yet. Any other suggestions? Quote Link to comment Share on other sites More sharing options...
denny411 Posted January 6, 2004 Share Posted January 6, 2004 Bad or weak struts will cause this problem, as well as worn joints or loose and/or improperly torqued wheel bearings. Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted January 6, 2004 Share Posted January 6, 2004 Out of round tires or tires with flat spots from brake lock up will also. Also "warped" brake rotors will cause slight vibration while cruising, but significant vibration under braking. Quote Link to comment Share on other sites More sharing options...
Tim240z Posted January 6, 2004 Share Posted January 6, 2004 Have the balance rechecked. You could also try having the wheels high speed balanced (on the car balancing). Off the car balancing (static and dynamic) is usually only accurate to about 5 grams. On the car balancing (if you have a good operator) can be accurate to <1 gram. Tim Quote Link to comment Share on other sites More sharing options...
Phantom Posted January 6, 2004 Author Share Posted January 6, 2004 OK - replies have caused me to think a bit more. Ever since I installed these wheels & tires I've had vibration problems but Discount has always been able to balance them out. I think I'll go back to them again though and have them take another shot at it. However, some things have happened fairly recently: 1) I did a sliding stop from 35-40 mph to keep from hitting a guy that pulled out in front of me, 2) The engine/transmission conversion has been done and the driver side radius rod mount was modified slightly, 3) New urethane bushings have been installed in the suspension (struts & springs only have about 40,000 miles on them), 4) the steering rack was "realigned" and new bushings installed in it. The car also has new tie-rod ends and ball joints with about 30,000 miles on them. Quote Link to comment Share on other sites More sharing options...
Tim240z Posted January 6, 2004 Share Posted January 6, 2004 Make sure you have them run the wheels on the machine BEFORE pulling all the old weights off the rims. That way you'll know. The S.O.P for tyre shops is to yank the weights, then spin the wheels, which won't tell you a thing. Tim Quote Link to comment Share on other sites More sharing options...
denny411 Posted January 7, 2004 Share Posted January 7, 2004 Try rotating yourtires from front to rear and check to see if it rides any shmoover. Quote Link to comment Share on other sites More sharing options...
GAZRNR Posted January 7, 2004 Share Posted January 7, 2004 I completely rebuilt the front & rear suspension of my 78 Z. All new hard parts, bushings, struts, springs, tires & all. The car had a terrible shake at highway crusing speeds, had the rims checked for true, made sure the wheels were not over tightened, did the tire swap, had the tires rebalanced a couple of times and got the tire dealer to warranty 2 then the other 2 tires and no relief. Then started to play around with cold tire air pressure. Found that 26 in the front and 30 in the rear gave me a smooth ride up past 100 with no shakes and the car became fun to drive. You may want to try adjusting tires pressures only after a good alignment and proper tire balance & rotation. This worked for me...good luck! Quote Link to comment Share on other sites More sharing options...
Phantom Posted January 7, 2004 Author Share Posted January 7, 2004 Tires were rotated when they were balanced and the vibration continued, although was a bit less. I torqued the wheel bearings on the '83 but I don't think I've done them recently on the '77. Here is plan: 1) Check torque on front wheel bearings. 2) Have 4-wheel alignment done. I haven't had one in 100,000 miles so it just might be due. 3) Check and ensure the T/C rod nuts are properly tightened on both sides. 4) Have Discount rebalance the tires with me sitting on their head. Quote Link to comment Share on other sites More sharing options...
Phantom Posted January 26, 2004 Author Share Posted January 26, 2004 Follow-up. I pulled each front wheel and ensured the wheel bearing torques was correct and torqued the lug nuts to 70 lb.-ft. with the wheels off the ground. The front-end vibration diminished a bit which indicated to me that the tires had probably not been balnced per my specs. Took the car back to Discount and they "balanced them the way they do a BMW". Turns out BMW's are a bit sensitive so they used that procedure. I told them to use weights on outside of rims if necessary to get balance right. They had only used them on the inside. One wheel took 3.5 oz of wieght, another took 4 oz of weight to balance. In each case - half on the outside. Car is MUCH smoother now but still has very slight vibration starting around 80 MPH. I'm putting it in the air to thoroughly check suspension/steering components tomorrow to see if a worn or loose part may be contributing. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted January 26, 2004 Share Posted January 26, 2004 IMO it is ALWAYS necessary to put weights on the outside of the tire to get a correct balance. Inside only = static balance. Both sides = dynamic balance. For rims without lips (man I hate those) the wheel weights can be stuck on near the spokes towards the outside to get the same basic effect. I had a similar problem where I took my car in and the guy didn't want to put weights on the outside of my rims because it looks bad. He had owned his tire shop for 20 years, and was sure that since the machine was a "Dynamic Balancer 4000" or whatever that his machine would ONLY do a dynamic balance. I tried to convince him otherwise, but he started to get pissed off. So I drove the car away and came back an hour later and actually got into a pretty big argument before he took the wheels off and fixed it. They had a really bad wiggle at 65 mph to 75 mph in my case. Jon Quote Link to comment Share on other sites More sharing options...
Phantom Posted January 27, 2004 Author Share Posted January 27, 2004 Got the car in the air today. Several bits of good news. First the shop guys were amazed at how good of condition my undercarraige/subframe connectors were in. There was no evidence of rust/deterioration. One of the "problems" in the front suspension turned out to be "normal" and we also identified a couple bushings that still need to be replaced that are pretty deteriorated but still functional. Once they are replaced I will be solid in the front. The unknown noise in the right rear I had been worrying about turned out to be real - but minor. The long bolt that attaches the lower a-frame to the body was loose and backing out. I was hearing it rub against my sway bar. Tightened it up and everything is ok again. All the other bolts back there got checked along with the half-shafts and their u-joints too so I have peace of mind again. It's really nice to have several guys gather under an old Z to be amazed at how clean and rust-free it is. Best part was that they did it for free just to get a look at the car. Quote Link to comment Share on other sites More sharing options...
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