Ducman82

Thought i had flat spots on my from tires, so i got new ones. 80-85 MPH i get a nice oscillation or "vibration/rhythmic shake/pulse". tires are new, balance is spot on. changing tires did nothing. wheel bearings check ok, preload is just fine. Front suspension bolts all are fine and torqued......

Greg wants me to have someone look at the wheels while on the freeway at speed...... working on finding someone...

bad shocks? wtf?

Lizard928

Has Bill Ball sorted out his rear end vibration?
Maybe you two can meet up and look at each others ends?

Tomkat80222

I get a vibration at 70 mph. I was thinking of having the tires road force balance to see if that helps.

77tony

Tom, when those FM5's were balanced I remember the tire pro saying that he was amazed how little weight (if any) was added to get the rim/tire combo balanced properly. Might want to check elsewhere. T

soontobered84

Tie Rods??

928GTR

Steering rack bushings, or front spoiler or lower plastic panel loose?

Bill Ball

We're not close by, although we were at Sharktoberfest.

I've had the same high speed vibration for maybe 5 years. Three different sets of wheels and tires, new axles. Front wheel bearings, tie rods and ball joints OK. I replaced the front upper control arm with 928 Intl rebuilt units and the rear upper control arm bushings even though they were not obviously deteriorated. Replaced front lower control arms with better used units even though they were not obviously bad. Despite the vibration which comes on about 80 MPH, I have traveled to Texas and back, etc. Most of the time the shake is through the body, not the steering wheel, so I've focused on rear end. Since it's road speed related, it would appear to be diff back, although nothing I've changed has improved it, including a tranny/diff swap. In theory, it could be rear wheel bearings, BUT it has not worsened in 5 years. I would have expected the bearings to do more than cause a relatively stable level of vibration after another 50K or so miles. I plan to change them soon anyway as they have more than 100K miles on them, but I don't see that as the cause. Now, OCCASIONALLY the steering wheel vibrates as part of the over all shake, and the shake is occasionally completely absent.

I'm still baffled. I have thought about loose panel vibration, as 928GTR suggests. Part of the panel system around the air opening in the front bumper is broken and could move around/vibrate, but I can't believe that would shake the whole car as much as I feel, but since the shake is somewhat capricious, although not clearly wind speed related, I've been considering something like that.

95% of the time vibrations like this are due to tire imbalance or some tire/wheel defect. I had a another similar vibration maybe 10 years ago after getting some new tires. I had the tire balance rechecked and one wheel was an ounce off. Rebalance fixed that vibration. This time, so such luck.

FredR

Bill,

I would not touch the rear wheel bearings unless and until I heard some noise intimating failure from them as happened on my late S4 many years ago when the grease seal failed and the grease dried out but then I know how you like doing such jobs!

Regarding mystery vibrations on the front end I often wonder how many of these are down to tyre fitters just whacking on a stack of weights to satisfy the machine when they should be force balancing by rotating the tyre on the rim to a more optimally balanced "natural" position. Not saying this is the cause of the OP's or your problem but perhaps should be eliminated from the list of possibilities if such is not the case already.

The last thing wheels are is round- they are all ovaloid to within set tolerances considered to approximate them being round enough!

Rgds

Fred

safulop

I had a 944 years ago and this was even more common in that model. So much so it was nicknamed "the 944 shimmy." It was generally attributed to the suspension geometry making the front end unusually sensitive to tire issues and even wind. Road force balancing should help, from my experience.

Jerry Feather

My 87 started a vibration on a 500 mile trip to Denver and back, but only when I got to and exceeded 80 mph. I had to keep it at or under 75 for the bulk of the trip. By the time I got home and when making the street corners near my house I began to feel the clear wheel bearing grinding on one side of the car, the left rear as I recall. I concluded the issue was a rear wheel bearing.

When I jacked it up and began the process of replacing the wheel bearing on that side the first thing I noticed was how the axle nut was not very tight. It was not finger loose, but I don't think there was any torque on it at all. Then when I got it apart I found that one of the bearing inner races had hammered itself around the hub so much that the hub was essentially destroyed. The hammered grove around it was probably .025 in deep all around.

I replaced the hub and the bearing and then did the bearing on the other side, for good measure.

So, in this thread, I have to wonder why the title suggests the front of the car when the body of the first post does not seem to be focused there; and I wonder just how the bearings were checked ok.

Ducman82

Good idea. ill check the rear as well.

i figured the front being the issue due to the steering wheel vibrating as well (not all the time).

Mrmerlin

I would add this bit of info I was following/ riding alongside an owner with a broken front block off plate and after we got to about 70 MPH it was interesting to watch the panel blowing back and forth into the tire,
the wind seems to have a good time with loose front end panels.
Now this was as i recall an early car and it was missing the metal plate position holder.

The S4 version is devoid of the metal plate and is now anchored to the spoiler.

I also saw an S4 with the panel bulging at speed though it didnt appear to be hitting the tire.
Might be worth a check ,
also make sure the temp sensor tube isnt blowing in the wind

hacker-pschorr

I'm sure your shop is fine, but any vibration always start with tires and find a shop with a new or almost current generation road force balancer.
I've seen wheel's / tires come off an older style machine balanced perfect, the road force machine disagreed. These new systems do more than just balance the tire too. It's quite fascinating playing with these new tire machines.

Just reticently I had a wheel weight come off, could be something that simple too.

RennPartsDirect

Have you checked your front wheel bearings? Mine need to be replaced and mine has a little bit of wobble on the highway...

Mrmerlin

also look for the inner hoop of the rim to be out of round