Vibration Diagnosis Tips

[excalibur]

Ok, I have a '68 1600 with Z snowflake wheels that I am trying to diagnose a vibration on. You primarily feel the vibration in your butt when driving above 45mph, but there is also a bit of shake in the steering wheel at this speed. I had new tires put on and balanced, and that didn't cure the problem. I'm figuring the vibration is likely something else.

My understanding is it is likely caused by one or more of these items:

1. out of balance brake drum or rotor
2. out of balance drive shaft
3. bad u-joint
4. Bent wheel
5. Out of balance / out of round tire

Like I said, the tires were bought new, and the vibration is the same as before, so likely not a tire issue. The car is also stored on jack stands with the tires off of the ground for the winter to prevent flat spots. Anyone have any tips on how to diagnose this one? It's been driving me crazy.

[spl310]

Stop driving on frost heaves? LOL!! It is tough to diagnose from descriptions. I would have someone drive beside me on a highway and watch the wheels to see if there is anything bent - either a wheel or an axle. Is there any noise with the vibration?

[23yrRebuild]

Front end alignment?

[excalibur]

I'll be able to drive it again in a week (seasonal registration) and will have my wife check to see if anything looks weird.

No, I have not gotten a alignment done. Will being out of alignment actually cause a vibration? Never heard that one. It does wander a bit on the highway, but I attribute that to the significant ruts in the road made by cars that have a wider wheelbase.

[notoptoy]

I would take a good hard look at the rims. On the impala, I bought new rims long ago. I battled a wobble from day one - after balancing, brakes, bearings, alignments and even A-arm bushings I was sure the tires were bad. Replaced the tires, wobble still there (up to 35 MPH, gone after that). When I had the second set of tires mounted, I specifically asked them to check for warpage - on the balancer, it showed up immediately - turns out you have to ask them to actually look at the rim - they had always just run the machine and put weights where the computer told them. Two of My wheels were bent, from new. I was able to get them trued locally for about $35 each. BTW, you could NOT see the warpage driving along side, but it was really apparent on the balancer. don;t trust computers!

[SLOroadster]

Could be a bad tie rod, I had an issue like this for a little while, it was there on 2 sets of wheels, on any pavement surface, replaced the right side tie rod and issue solved.

Will

[spl310]

The reason that I suggested an alignment is that the shop would see/touch your suspension and if there is something amiss, they should spot it.

[Alvin]

I bet it's the wheels
do you have the correct lugnuts/washers, etc. to run those rims?


Have you tried running some stock wheels/tires to duplicate the vibration?

[excalibur]

Unfortunately, I do not have another set of wheels/tires to try out. I am using a washer with a high-profile lugnut to fit the wheels.

[Alvin]

hmmm...stock wheels would be the easiest/quickest way to rule out snowflake mounting.
On the 280Zx iron cross rims I had to use specific washers and a machined sleeve in the lugnut holes, other wise the nut would "float" around, causing a vibration

[spl310]

Did you get those sleeves from Mike Harper?

[Alvin]

no, who is Mike Harper?

[spl310]

http://www.team.net/mharc/archives/html ... 00304.html" onclick="window.open(this.href);return false;

[Alvin]

that's a trip!
I didn't even know about the list in '01
Francis gave me these sleeves and spacers in '02 though

[spl310]

He may have gotten them from Mike. There was a huge discussion back then and I suggested the sleeves as the lug nuts were tough to find. Mike got them done and then someone found the lug nuts at wheelcomponents.com so Mike had a pile lying around.