Vibration issue after 100km/h

[crusher]

Hey Guys..

My Parents bought a 1998' 740i and they're having issues with vibration after 100km/h. The vibration got worse when they switch to summer tires, they had Autohaus BMW perform the alignment and they cant seem to fix the issue. Any idea whats wrong?

Jeff

[Maxim]

Bent wheels, Worn thrust arm bushings

[Seven]

Could also be a worn strut. Worn suspension components = uneven wear on tires = vibration at certain speeds.

[bimmerjoe]

out of balance wheels/tires

[AceOfSpades]

control arms?

[oafguy]

I'd have to agree with this one. I had that problem at 100/km. got the wheels rebalanced and everything is sweet now.

Originally Posted by bimmerjoe

out of balance wheels/tires

[740-iLL]

I just got my 20" TIS Wheels put on and I am having some wierd vibrations similar to the OP, both in the steering wheel and in the seats, once I hit 70 km/hr all the way to 90 km/hr, but goes away after 90 and before 70.

went back to the place that installed them, they had balanced the tires infront of me, and they are perfect. he said that with the size of rims, and the low profile tires 245 / 40 / 20R, that it is common to have these vibrations. I'm VERY used too the smooth ride of the 7, and this feels too out of place.

Any idea's or concerns as to what could be causing this?

[Maxim]

Originally Posted by 740-iLL

Any idea's or concerns as to what could be causing this?

Worn thrust arm bushings are a very common cause of high speed vibrations on 5s and 7s.

[slemmer]

Try rotating the tires if they are not staggered. It could be belt issues.

[S54]

Replica wheels will also contribute, my personal experience.

[RMPMOTORS]

If the wheels are balanced and True, it could the the thrust arms!

[Max_VQ]

The above is good advice!
Also, make sure there is not any rust or debris on the hub where the wheel mounts. If there is use some 80 grit sandpaper to get it down to bare metal, and cover the hub with a little anti-seize.

[chia]

Sorry to bump an old thread. I picked up 18" RSGT replicas for my e36 M3 yesterday.

While driving home, there is significant vibrations in the steering wheel and seat. It occurs at ~100km/h+... and the car somewhat pulls to the right.

At some points there is also a lot of sudden "bumps" and the car feels like it's rocking up and down.

From what i've read, since this occurred right after installing the new rims and tires - it's probably either bent rims or balancing.

I'm calling the guy back, but is the problem distinguishable when the vibration goes away if i'm turning? or on a bend on the highway?


*EDIT: My bad, I didn't know this thread was under 7 series.

[shelby guo]

wheel balance,check the bearing

[BimmerGuys]

If its not the tires/rims/bearings/control arm it might be the frame itself. Any previous accident on the car?