[N.I BMW Owner]

I too have a road rumbling 320d M Sport G20 2WD, manufactured June 2019 with an ‘F’ at the start of the last 7 digits of the VIN/Chassis No.

This is our 5th BMW 3 series, and never would have suspected such a serious design problem.

We only took a very short test drive at low speeds and the sales guy was talking a lot, so we never noticed anything until we had the car home.

We took the car back after two days as they were not open to do so quicker, and asked for a refund, as we had then discovered online that many people everywhere/elsewhere were experiencing the same road/tyre noise problem.

They refused a refund and said we could leave the car for investigation as they admitted/agreed that the noises were obvious when we took the sales man out on a main road, however once the sales manager got wind of our complaint, he insisted that ‘it’s probably just a natural characteristic of the car’!
Meaning that they knew about the issue, got the car sold to us and now we can just keep it as it’s now Registered and there’s probably nothing dangerous about it.

I’m actually a mechanic by trade and have good knowledge of the industry, but broke my own rule of never buying the first year of any new vehicle design, to my peril!

Anyway, as I was getting no positivity at the selling BMW dealer other than they offered to get a mechanic drive the car about after hours, to their home etc., I decided that I’d nothing to lose by investigating the fault initially myself.

Our previous car was Road quiet and had Good Year RF tyres, so we changed the front tyres to Good Year Eagle F1 Assymetric 3 RF, as they have a lower DB rating. This didn’t help a lot, but had some minor influence.

The car had only 3k on it and had probably been lying around due to lockdown, so there was some corrosion minor on the brake disk edges. When the car was lifted off the ground and the wheel rotated there was a grinding noise, so we decided to order genuine BMW discs and pads and fit them. This resolved the scraping noise, but a on test run, the road rumbling was still there!

However, when I had the brake discs off, the hub carriers and the bearing/hub assemblies were exposed. It all looked very inferior in comparison to the rather robust looking M Upgraded Brakes and the upgraded adjustable shock absorbers.

Also the Front Hub carriers are made from an Alloy Aluminium which may be one of the main sources of the rumbling.
There’s always going to be road to tyre noise where rubber meets the road, but if the suspension is acting like a magnifying device, then the noise will amplify and Could be noticeable inside the car.

The front hub and bearing assemblies are also very inferior looking for the size and performance of the vehicle, especially in comparison to the appearance of the brake assembly. The front wheel hub/bearing assembly is a preassembled component meaning that it cannot be recalibrated/checked for tightness, or dismantled. It bolts to the hub carrier, so is easy to change, if required.

The X drive variant of this car has different front wheel bearing assemblies to allow for a front drive shaft. The effect of adding front drive shafts, will add weight to the front hubs, which will act naturally as a resonance damper, so the rumbling may not be just as noticeable on X drive vehicles.

The brake disc backing plates are also quite large, flimsy and ultimately are acting like amplifier devices for undesirable noise. The shape of the disc backing plates also invites small stones to be caught between the disc and the shield. I’ve already had to remove the road wheel to dislodge a trapped scraping stone!

In a further attempt to reduce the road noise, we cleaned the inside of the braking plates and added alloy wheel balancing weights, which changed the natural frequency of them, reducing the tendency of the plates to amplify road noises. However, this too didn’t solve the general rumbling issue.

The body shell also may be part of the problem, as it features Aluminium inner wing panels and as BMW boasts a 20kg weight saving over the F30 predecessor, the vehicle, many areas look thinner and lighter/cheaper.

I suspect that BMW will not wish to admit to design faults, as this would have large financial implications to rectify, and it’s unlikely that components would become unsafe even though there’s no customer satisfaction.

However, if there is a confirmed solution, which involves several components being changed to eliminate the issue I would be keen to hear about it.

The car performs Very well in almost every other way, so it’s a shame if this rumbling road noise cannot be resolved.