High speed vibrations, need ideas

[CarsSuck]

My '89 325is has bad vibes. Right around 75 it gets the shakes and the steering wheel shimmy. The shimmy gets more intense going around broad interstate turns, but also exists while driving straight. The car tracks perfectly straight.

I've rebuilt the entire suspension, shocks, tie rods, new CAs and bushings, strut mounts, rear bushings, rear wheel bearings, the whole shebang. That stuff has about 30k mi on it. Front wheel bearings only have about 15k mi on them. I've inspected it all, and it's tight. This led me to the drive shaft. I replaced the CSB this weekend, which helped a little with the straight line vibes. The rubber was intact, though the bearing was rattling. The u-joints weren't seized and had no detectable play. I've also tried two different sets of wheels and tires and now have brand new falkens on the front.

I don't know what else it could be. The steering giubo is original as is the rack, so i suspect the rack may be worn out, but i have my doubts about that as there is only a small "dead zone" at center.

As far as alignment, I had it aligned to spec a while back. The guy at the shop (guy tracks a 318is) recommended that I set the toe to zero, which after driving the car for a bit (with this vibration) i took it back and had it realigned for zero toe. I thought the car felt more stable and was less darty afterwards so that is how its been. Is anyone here running zero toe? It has been a long time that i've been chasing this and I'm just about out of ideas.

Sorry for the novel.

[nando]

bent/out of balance wheel?

[dnguyen1963]

Check your tires too. I had a small bulge on a side of my tire once and it caused a similar problem.

[CarsSuck]

like i said i had on multiple sets. This was my first thought as well since my weaves are pretty badly curbed. But I put on my perfectly straight SSRs with brand new tires. It made no difference. And now im on another set of front tires that are also brand new and I'm told balanced just fine.

[CarsSuck]

Check your tires too. I had a small bulge on a side of my tire once and it caused a similar problem.

yea, one of my shitty sumitomos had a kinked belt/crack in the sidewall.

OT: there arent anymore 205/60/14 tires anymore I had to search a bit just to find some falken 512s in that size

[AndrewBird]

Adding toe will make the car more stable. I don't really see how toe could create a vibration though.

Has the car ever been in an accident that you know of? Maybe the frame is tweaked and is causing weird things to happen.

[CarsSuck]

Meh, its been in some low speed collisions. It had a clean carfax and all the panels had their VIN stickers. It didn't always have this problem. I've had the car since '04.

My dad mentioned that a little toe in loads the tie rods...don't know though. It was similar either way.

So worn out rack? How does one diagnose that?

[Jaxx_]

if everything feels tight I'd still go back to control arm bushings. I know that they're fairly new, but they can seem tight even with handled with a long pry bar.


does it clear up as you go faster?

[Farwest92]

I recently went through the same process you described, which is to replace all the things. The last of the vibration didn't go away until I replaced the stock rack with an e36 rack. The old rack had no obvious signs of wear, I just wanted the upgrade. I also started with toe in, which was stable but killed it in the corners. Zero toe is much more responsive in the turns. Suggest a new rack.

[bmwstudent]

i know you don't want to hear it but check the wheels and tires again. Vibrations transmitted through the steering wheel usually end up being in the wheels and or tires. Even if you were told those Falkens are balanced "just fine." If its coming through the steering wheel its probably not related to the driveline. Good luck, bad vibes suck.

[Quinthirty]

I finally got to ran my car at high speeds over the weekend. We were probably going around 160-180kph (speedo broken), with another guy in front of me with his E30. I suddenly noticed a vibration that I didn't experience in lower speeds. I noticed some slight feathering tire wear on the rear right inner tire. What could it be? Could a bearing do that? I hear a low hum on the back rear. Sub-frame, bushes, and lollies are new. Shock doesn't have a leak and has good damping.

[JonnyOg]

I finally got to ran my car at high speeds over the weekend. We were probably going around 160-180kph (speedo broken), with another guy in front of me with his E30. I suddenly noticed a vibration that I didn't experience in lower speeds. I noticed some slight feathering tire wear on the rear right inner tire. What could it be? Could a bearing do that? I hear a low hum on the back rear. Sub-frame, bushes, and lollies are new. Shock doesn't have a leak and has good damping.

Interested in the response, I have the exact same symptoms although my vibration starts at about 120kph.
I'm going to be doing the weld in tabs for the subframe pretty soon, hopefully that helps.