Z4 35i Sport DCT, vibration in the back...

Z

Z435iFI

Member
Hello all, I am glad I found this forum.
I got my Z4 35i M Sport with "Sport DCT" a month ago (it is MY 2013, some 5000km in the clock when I bought it) and now trying to survive through the ice and snow.
Anyways, there seem to be some problem either with the drivetrain or the rear wheels, and I suspect the former as I have had the wheels re-balanced already. The car still has some of the warranty left and I took it for inspection. The BMW repair shop did not find anything unusual. But the vibration is there. It is not always but only occasionally. It does not come through the steering wheel but rather one feels is through the seat.

I wonder if any of you have experienced anything similar with your Z4s? If so, have you found the cause for it?

Somewhere else in this forum I saw somebody mentioning about the problem with ice in the side windows. I have it too and it is driving me crazy as the window does not lower the 10 or so mm to let me open the door. In my earlier E92 I had similar frameless doors and no problems with the windows. So it seems they have done something differently in E89. Maybe the thinner insulation in the roof makes it prone to icing? Any remedy found for it?
It seems the freezing takes place up in the roofline preventing the window from lowering then. So if I used some silicone or something similar in there, that would not freeze, maybe it would solve the problem. Maybe.
 
InvisibleName said:
Gummy Pflege around the inside of window seals - sorted!
Click to expand...

OK so the vibration. Could you give us more information? Is this at a certain speed, certain revs, under certain conditions or certain roads or surfaces etc? Is it low frequency like a bounce, or high frequency like a buzz? Is it audible in any way and if so, from the front or rear?

As others may recall, I have a vibration around 30mph, but I tracked that issue down to the tyres after exhaustive and expensive time in dealers and an indy only to find nothing wrong with the drivetrain.
 
Hello Maniac :)
this vibration is rather low frequency and low amplitude, something similar to what a slightly "unbalanced" rear wheel could generate. But as said, the wheel balancing was checked already by the dealer, and the specialist was told what we were looking for, so I want to believe he did a good job.
This is not speed dependent. I have had with some earlier cars some tyre unbalance issues that "resonate" at certain speeds. This is not like that at all.
It seems it is more likely to appear right after starting to drive, rather than a long after the start.
There is no noise or sound but it is just what one feels through the seat. Some of the passengers have no idea of any vibration but then some other, more "skilled in the art of cars", do recognize it without I having to tell them first.

It is kind of bothering since my personal "vibration filter" has already been tuned to its frequency. So I definitely recognise it as soon as it starts.
 
Maniac said:
InvisibleName said:
Gummy Pflege around the inside of window seals - sorted!
Click to expand...

OK so the vibration. Could you give us more information? Is this at a certain speed, certain revs, under certain conditions or certain roads or surfaces etc? Is it low frequency like a bounce, or high frequency like a buzz? Is it audible in any way and if so, from the front or rear?

As others may recall, I have a vibration around 30mph, but I tracked that issue down to the tyres after exhaustive and expensive time in dealers and an indy only to find nothing wrong with the drivetrain.
Click to expand...

+1 to this!

First make sure the tire and wheels are OK, then move to more complex elements.

Regarding the tires - does it come with the manufacturer originals (usually Bridgestone Potenza RFT)? If not, make sure the tires are the correct size and load/speed ratings. You can see the correct tire specs in the driver doorsill. Also look for any damage, both on the otuside of the tire and in the inside (you will probably need to dismount the wheel).

EDIT: Found this post about car vibration felt throught the seat. In this case the wheels were bent. http://www.bimmerforums.com/forum/showthread.php?1324754-Low-speed-vibration-not-wheels-tires-issue
 
Z435iFI said:
It is kind of bothering since my personal "vibration filter" has already been tuned to its frequency. So I definitely recognise it as soon as it starts.
Click to expand...

Oh I can certainly relate to that. Every niggle feels like a third world problem at first.

I'd take the advice above and get the wheels checked first, if you're happy with the tyres being ok. Move on from there.
 
+1 for a buckled wheel. It will still balance perfectly, but if not round, it will resonate, although I would expect it to be worse at certain speeds. I have a 3-4mm buckle in a front wheel which is barely noticeable.
 
If its not speed dependant, what about the exhaust system mounts. has it taken a knock and has 1 or 2 under stress and its this causing the problem. This happened to me when i had a tow bar fit to my 525d F11. the bar used the same bracket to mount the rear exhaust hanger, but it was pushed out of position by the thickness of the tow bar. In cold conditions you could tell there was a resonance under drive that was not there previously.
 
I have to assume that the wheels are fine. I have had them checked twice now !
Sooner rather than later I will have the chance to lift the car up and do some inspections of my own. If nothing found, then I will wait until I get rid of my winter tyres and see if the problem exists with summer wheels.
Thanks for the tip about the exhaust mounts, dario.
 
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