E90 2008 335XI 6AT, minor vibration 58-65mph

[ls3c6]

Have a low hum (maybe 50hz?) and not loud, say 50db hum/shimmy/vibration precisely between 58 and 65mph. Tires have been balanced several times, this is NOT a wheel bearing noise... I did inspect the front driveshaft however I did not remove the exhaust/heat shield to inspect the rear driveshaft/guibo/center bearing.

This condition is not affected by load or suspension travel / movement or even rpm. It is strictly speed dependant and tends to lessen/worsen day to day.

It's something most wouldn't notice and I've been told it's tires... but I don't want to replace half worn tires to find it isn't, any pointers?

[Yurick]

I'm tempted to say that it is the tire balance or the tires themselves.

[ls3c6]

Originally Posted by Yurick

I'm tempted to say that it is the tire balance or the tires themselves.

they've been balanced several times, I hate to buy new tires and find that's not it though.

Would center bearing or flex disc cause these problems?

[Dachyi]

I had this problem many time in my workhop ... every BMW series.
But usually this problem comes up after 70.000 miles or ... starting after 5 - to 6 years of driving.
And mostly itīs the flex-disc.
If not 1 out of ten, it is the center mount bearing - for the flex disc itīs esy to check visually on cracks.... the center mount you can check by lifting the drive shaft up and down - there shall be no noticeable clearance.
If itīs the wheel/tire balancing, it will not disappear above 58mph - it will get harder with rising rev.

[ls3c6]

it doesn't BEGIN until 58mph, it is a 2008 335xi with 91k miles

[ls3c6]

Drove a 2010 335i XDRIVE last week, 60k miles... exhibited the same driveline drone / hum, but even a little worse. This car had brand new tires and no abnormal wear.

I wonder what it is, I sure hope it isn't normal