Wobble noise left rear on small bumps

Greetings.

My 09 has developed an odd noise like a wobbling/banging in the left rear wheel area while driving over little bumps. Things like pavers/reflectors/other repeated small bumps driving around town. I thought it might be an issue with a freshly patched tire so I replaced with a new tire. Issue remains. I've removed the wheel and inspected the hub and areas around with a quick look twice now. I can't figure out what it is. I've pulled and shoved on whatever I can get my hands on but everything seems solid. Even bounced the car up and down to try to recreate. Pulled on the wheel in the air, etc. Really stumped. It's a wobble/thump like some component in the rear suspension is loose but so far I cant find it.

Rear strut?
Strut mount?


or:
Subframe bolts?
Bushings?
Wheel bearing?



80K on the car.

Appreciate any suggestions.


I got a little bored and decided to go after the rear strut upper bushing/bearing whatever it's called.
Does this look normal? It's off center and appears to be shedding rubber. this entire assembly moves up and down inside the car when I bounce the car. I assume that means that something has failed under the car which is allowing this to move upwards. Looks like there is a repair kit which includes a lower bushing/washer. Shock Mount Repair Kit 339810 - BMW (33-52-2-406-280). I suspect that is what has failed. Anyone have experience replacing this?

Update:

Rear shock mount is toast. Hoping this resolves the issue. Ordered part #33-52-2-406-280

Edit: this kit does not fit the EDC shocks. RealOEM listed this kit as S223A=YES so I assumed it would be good. Bimmerworld has an assembled kit for EDC here: https://www.bimmerworld.com/Suspension-Steering/Urethane-Bushings/Rear-Shock-Mount-3-piece-BMW-E9X-M3-EDC.html. Going to try that instead.

I appreciate when people follow up with the solution. 👍
If original, what is the mileage?

TX wrote

Update: Rear shock mount is toast. Hoping this resolves the issue. Ordered part #33-52-2-406-280

That's a rare failure. Does South FL have a lot of potholes? Have you driven over one recently.

Car has 80K miles.

DW_CT9A wrote

I appreciate when people follow up with the solution. 👍
If original, what is the mileage?

DrFerry wrote

That's a rare failure. Does South FL have a lot of potholes? Have you driven over one recently.

Most of the roads here are rather good. I've seen much worse roads in the northeast. Florida is very humid and hot 80 to upper-90's a good bit of the year. I don't remember hitting anything. Mostly, it just looks like the rubber/foam around the lower guide support has completely dry-rotted away. Here's a picture of what it's supposed to look like. I only found the remaining powder and the metal tube when I removed the components.

TX wrote

Most of the roads here are rather good. I've seen much worse roads in the northeast. Florida is very humid and hot 80 to upper-90's a good bit of the year. I don't remember hitting anything. Mostly, it just looks like the rubber/foam around the lower guide support has completely dry-rotted away. Here's a picture of what it's supposed to look like. I only found the remaining powder and the metal tube when I removed the components.

Glad to hear FL roads are quite decent. Up here in South Carolina the roads are full of potholes. They are some of the worst roads in the nation. When compared to roads in Kentucky (which some of the best in the USA from what I've experienced), South Carolina roads resemble Beirut! But then again Mitch McConnel was the KY Senator for decades (1985 to present) --- follow the money. I digress.

Foam rubber bump stops - like the one shown in the photo you posted - degrade over time and are sensitive to ozone in the atmosphere. Some areas of the USA have more ozone than others e.g. the L.A. Metro area as well as others. FL high heat and humidity don't help - but I suspect salt in the atmosphere from the ocean doesn't help either. However, that's speculation on my part. If your car spends time parked around electric motors (workshop, machine shop, construction etc.) then ozone from these sources could be accelerating the foam rubber degradation.

Well done sleuthing the wobble noise root cause, finding the crumbling residue, and thanks for posting on the subject, as well as the part numbers. Good luck with the repairs.
.
https://www.applerubber.com/hot-topics-for-engineers/understanding-the-link-between-ozone-and-rubber-deterioration/
.
https://www.coirubber.com/ozone-and-rubber-deterioration/

Thank you for your detailed write up. That would make sense.

I’m currently trying to decide if the shock is bad and should be replaced while I do the mounts. 09 with 80k. I can depress the shock with my hand and do not know if this is normal or a sign that it might have failed. Is there a test to determine if it needs replacement?

DrFerry wrote

Glad to hear FL roads are quite decent. Up here in South Carolina the roads are full of potholes. They are some of the worst roads in the nation. When compared to roads in Kentucky (which some of the best in the USA from what I've experienced), South Carolina roads resemble Beirut! But then again Mitch McConnel was the KY Senator for decades (1985 to present) --- follow the money. I digress.

Foam rubber bump stops - like the one shown in the photo you posted - degrade over time and are sensitive to ozone in the atmosphere. Some areas of the USA have more ozone than others e.g. the L.A. Metro area as well as others. FL high heat and humidity don't help - but I suspect salt in the atmosphere from the ocean doesn't help either. However, that's speculation on my part. If your car spends time parked around electric motors (workshop, machine shop, construction etc.) then ozone from these sources could be accelerating the foam rubber degradation.

Well done sleuthing the wobble noise root cause, finding the crumbling residue, and thanks for posting on the subject, as well as the part numbers. Good luck with the repairs.
.
https://www.applerubber.com/hot-topics-for-engineers/understanding-the-link-between-ozone-and-rubber-deterioration/
.
https://www.coirubber.com/ozone-and-rubber-deterioration/

TX wrote

Thank you for your detailed write up. That would make sense. I’m currently trying to decide if the shock is bad and should be replaced while I do the mounts. 09 with 80k. I can depress the shock with my hand and do not know if this is normal or a sign that it might have failed. Is there a test to determine if it needs replacement?

If you can "easily" compress the shock by hand, or if you see oil seepage or leaking then the shock is probably bad.
.

DrFerry wrote

If you can "easily" compress the shock by hand, or if you see oil seepage or leaking then the shock is probably bad.
.


Thank you. The 2:10 mark in that video where he pushes it down by hand is where I'm at with mine. Guess I'll add rear shocks to the order. Cheers for the video.

Update 2: Pulled the shock off the car. It's toast. I can easily fully compress it down. It never returns. I assume this is not the correct behavior for a strut. Ordered a replacement set for the rear with hardware. Be careful as the EDC shocks on the E92 (33-52-2-284-311) and E90 (33-52-2-284-314) use different shock part numbers. I suspect loading/travel is different.

Yeah the factory EDC dampers on these cars don't tend to last all that long. It looks like the one you have laid down lost all it's nitrogen since it's not rebounding.

Don't forget you need to reset the aging calculation in ISTA.

https://www.m3post.com/forums/showpost.php?p=30944508&postcount=32
https://www.m3post.com/forums/showpost.php?p=30013077&postcount=9

RocketyMan wrote

Yeah the factory EDC dampers on these cars don't tend to last all that long. It looks like the one you have laid down lost all it's nitrogen since it's not rebounding.

Don't forget you need to reset the aging calculation in ISTA.

https://www.m3post.com/forums/showpost.php?p=30944508&postcount=32
https://www.m3post.com/forums/showpost.php?p=30013077&postcount=9

Appreciate the tip. I've gone through those posts. I see you mention a link to the procedures in one of your replies, but I can't seem to find the steps for ISTA. Do you have that handy still? Thanks.

Just run thru the procedure and execute. In your case, option #2.

My ‘09 M3 is going in the shop on Wednesday to investigate the same noise! I’ll definitely follow up with findings! I’ve been describing it as a metallic rattle. Car is at ~93k miles.

Thanks for all of your thorough follow-ups!!

Project is done. Replaced both rear shocks over the weekend with new mounts and hardware. They were totally shot. Amazing the difference in suspension feel. Noise is gone too which is nice. For anyone ever attempting this, invest in a 22mm ratcheting offset box wrench. I would have paid 5x the price for that wrench. That top shock nut blows. It's hard to turn and you have to remove the upper 10mm wrench to move the 22mm wrench after each half turn while reaching as far as you can into the trunk.

These sockets are worth a look. Makes the counter hold a lot easier. You can search with keywords strut nut socket or similar.

DW_CT9A wrote

These sockets are worth a look. Makes the counter hold a lot easier. You can search with keywords strut nut socket or similar.

I have those. The issue is that you have to remove both tools and wrenches because you’re going to hit the counter hold wrench after less than half a turn. The locking nut needs to be turned what seems like 20 full turns which is 40 removals to adjust the wrench at minimum hence the ratchet suggestion. Your arms and back will be very annoyed.

Sorry for the misleading post. I think these are useful to break torque and re-torque.
I just recently did this and I used a ratcheting flex head wrench. The offset might trump the flex head stability wise but the flex head was readily available and worked just fine.