Weird vibration at 90-100 mph - doesn't exist with extra weight?!

[Jand3rson]

What would cause my rear end to vibrate with no load, and NOT vibrate with an extra 300 lbs in the car?

Could be an out of balance or bent wheel in the rear, or one/both of your rear wheel bearings are bad.

[Sean]

Sorry Sean, he is correct. There is no adjustability anywhere in the rear of an E30. If the stealership told you that, give me their name and number...I wanna talk to that tech.

Luke

Ok - I guess I wasn't clear.

Yea, you're not supposed to be able to adjust - and I was under that assumption too.

However - they managed to. I specifically SAW the difference with my own two eyes. The problem with the rear is to dial out camber creates more rear toe in (I think) they can't be adjusted individually. I was SHOCKED when I got the sheet back to see they had dialed out my rear camber. I asked how they did, and the guy couldn't tell me. I didn't wanna stick around to ask the tech, so I left. But, I remember reading somewhere that the bushings can be pushed to different positions in the trailing arm - which mine were.

But, it was indeed adjusted. My camber was BAD - but wasn't as bad when it left the dealer.



For the sake of this arguement, lets assume it isn't adjustable.

What would cause my rear end to vibrate with no load, and NOT vibrate with an extra 300 lbs in the car?



Oh, and netcsk, didn't mean to sound like I was attacking you. I shoulda been more humble with my response, so I apologize. :)

[StereoInstaller1]

Wrong.

It is adjustable.

How else did the dealership dial out my -5 camber to -2.5 when I got my car aligned initially.

Sorry Sean, he is correct. There is no adjustability anywhere in the rear of an E30. If the stealership told you that, give me their name and number...I wanna talk to that tech.

Luke

[Sean]

the rear is not adjustable in the e30. You can only adjust toe in on the front wheels.

Wrong.

It is adjustable.

How else did the dealership dial out my -5 camber to -2.5 when I got my car aligned initially.

[netcsk]

the rear is not adjustable in the e30. You can only adjust toe in on the front wheels.

[Sean]

So, I've been meaning to post this, but school has had me busy OUT OF THE ASS like crazy. It's amazing how busy school has kept me.

Before I drove the 950 miles to school in August, I went on a couple test drives (drove to Pendleton, OR). I noticed then that when I passed speeds of $90 mph, I got a pretty substancial vibration from the rear of the car. Nothing shaking your jaw, but it sure shakes your butt a lot. I noticed driving home it was the same way.

On my way out to school, my car was loaded down. I actually added 10mm spring pads to both sides so I could support the extra weight without tucking massively. Well, the way out - I got NO vibrations. it was like it was before - solid as a rock and not a BIT of vibration AT ALL!

I thought - cool, maybe the pads got the car raised to the point where it was when it was aligned over a year ago.

I recently went for another drive, passing 90 mph - and sure enough the vibration has returned.

So, I'm thinking this. I had to change my subframe this summer since my other one cracked due to bolts falling out of my diff. Well, I figured since I didn't touch my trailing arm bushings that my alignment would remain identical - was I wrong? Did my alignment get tweaked?

I was going to get one before I left for school - but the oh-so-awesome dealer in Boise said they couldn't get my in until AFTER I had to leave. I couldn't seem to get across to the guy that I had to get in BEFORE a certain date. Fucking idiot.

Anyway, just wondering if what I'm thinking is right. If it is the alignment, does that explain why it didn't vibrate with the car loaded down?

That is all! I know it's long, but I like being thorough. :)