gabrielbecheanu

Hi
I've been driving an e250d from 2009 for a year, the car is in very good technical condition from a mechanical point of view, engine, gearbox, suspension.
it has only one small problem that bothers me and that I would like to eliminate.
at speeds over 160km/h, if I drive it at a constant speed, some small vibrations appear for a fixed duration, say about 3 seconds, after which they disappear and reappear after about the same duration, a more correct description would be: a vibration of a short duration but the same which appears and disappears with the same length as time.
Like a hum that appears and disappears with the same frequency and time

I followed to see if it has anything to do with a certain engine speed.

I specify that the engine has good buffers, the box is the same, overhauls on time, the DPF is clean, the wheels are balanced, I don't use wheel spacers
Thanks

Quint22

Wheel balance or wheel bearings come to mind. Another thing to look at more closely is the torque on the wheel bolts. Have had experience with over or under torqued wheel bolts/nuts and its caused various vibrations.

My top speed (that Ive gone accidentally) is like 90mph and funny thing at 85 or above it seems to smooth out (not that its rough at say 70mph).

BenzV12

Funny thing , I have also noticed something like that in a different car . The faster I go the smoother it drives
Back to the topic, it must be related to the wheel balance as well

S-Prihadi

The only time I had vibration at 160KM/H and then get worse as it goes faster was because my left rear tire, has a bad roadforce (uneven Radial Force Stifness ) value.
It was manufacturing "defect" of the tire.

Go and find Hunter wheel balancer with RoadForce capability.

See the left rear at 110Nm, that is way off the chart.



It took me lots pre-check to finally suspect that a new Michelin Pilot Sport 4 could be the fault.
Took months....



New replacement tire , I bought myself.





With all evidence of my other test and roadforce value, I claimed to Michelin Indonesia and I got a new tire from them in approx 30-45 days ( fresh stock )
I then use the tire for the other side. I roadforce balanced it too for sure : Below is the warranty replacement tire.





What is RoadForce balancer ?



I made claim to Michelin Indonesia and they approved.
I am the only one so far claiming replacement based on bad RoadForce value


Good luck............

gabrielbecheanu

thank you all for the answer. the wheels are balanced and equally tightened with a torque wrench. The bearings are well adjusted and without wear, so no noise. I am now using some all-season tires bought this year. but a lesser known brand. soon I will change the tires and see if this problem was from the tires. This vibration that I describe is not similar to the vibrations produced by poor quality and unbalanced tires. It is quite difficult for me to describe this problem.

S-Prihadi

TRANSLATED - Romanian
thank you all for the answer. the wheels are balanced and equally tightened with a torque wrench. The bearings are well adjusted and without wear, so no noise. I am now using some all-season tires bought this year. but a lesser known brand. soon I will change the tires and see if this problem was from the tires. This vibration that I describe is not similar to the vibrations produced by poor quality and unbalanced tires. It is quite difficult for me to describe this problem.


=============


RoadForce balancing machine can tell you if your tire is bad at certain section. A bad roadforce tire, its vibration is unique its more up-down and not shake left and right.

It is more of a Z axis vibration and not X



Have you actually use a road force balancer ?
It is NOT the same as ordinary balancer.

gabrielbecheanu

I heard about such a machine, but unfortunately in my city there is no such thing yet. But he will have a workshop in the future.