[bmw_solid]

I found this thread:
https://www.e90post.com/forums/showthread.php?t=331844

Studying pothole explosions...

Some mechanical explanations in that thread about this problem. Some are pointing towards a bushing that could be part of this explosion phenomena...

Coincidentally, I have a boxy rattle coming from the front suspension of the car when going over speed bumps or small sharp road imperfections... This noise is definately not normal, its like a loose arm or worn bushing noise...

I'm hoping, if I get down to this noise and replace the offending part, this could significantly lower the bang?? Because that boxy rattle that I get over potholes is very "contained" in the noise during the pothole explosion.... I know its a long shot, but just thinking whether that offending part is the culprit what many have thought the struts to be as the culprit....Why would BMW make a 3er that cannot satisfy normal road imperfections or why would their engineers not account for potholes? Its a really trivial and simple thing for them and even budget car brands to engineer....

Fingers crossed...

[bmw_solid]

Originally Posted by E92William

Loud bangs and noises were the name of the game when I got this car lol. It is awd but It had kw coilovers all around since I bought it. However what sucks about awd is that the struts are a bit shorter than rwd in the front though this shouldn't influence much. I think most of my bangs were from the run flat tires on the stock 17 in wheels which were horrid and rode like trash. I also had to replace a few suspension components such as thrust arm and ball joint which caused noise when going over bumps. Currently on non rft 18s and rides fairly good.

You should record this noise so people can compare to what they've dealt with.

Thanks,

I will definitely do a record of this noise in the coming days...

[bobbby]

2011 e90 with sport package

Refreshed struts with bilstein b4s and m3 front control arms at 100k miles. Everything else stock and original. Definitely still get the pothole explosions out here on shitty LA roads.

[bmw_solid]

Originally Posted by bobbby

2011 e90 with sport package

Refreshed struts with bilstein b4s and m3 front control arms at 100k miles. Everything else stock and original. Definitely still get the pothole explosions out here on shitty LA roads.

Its a mystery, even after changing to M3 control arms and Bilsteins, you're still getting pothole explosions??

I'm leaning more towards the idea that it could be something else rather than the shocks...thinking towards bushings or a loose joint/bolt, in-sufficient design of the strut mounts or a missing piece of rubber that the BMW engineers forgot to add into the suspension design.

If the struts were the culprit for these "explosions" why doesn't the back struts make the explosion noises? So far, all of the loud bangs I have experienced only come from the front....the back of the car either makes a thud or a quiet thud, never a loud bang...

[E92William]

The noisy rattle rubber clunk over small bumps is most often a balljoint. Mine was the thrust arm balljoints which had up and down play although very minimal.

[bmw_solid]

Originally Posted by E92William

The noisy rattle rubber clunk over small bumps is most often a balljoint. Mine was the thrust arm balljoints which had up and down play although very minimal.

Ok, thanks for letting me know. I think mine is really bad because (as I said before) it even rattles when going over sharp but small bumps and I am sure this rattle is also heard during the pothole explosions...

[bmw_solid]

Originally Posted by bmw_solid

New front SACHS oem-spec standard chassis shocks fitted yesterday inc. new Febi mounts, bump stops and protection/dust covers.

I changed the rears my self also with SACHS shocks.

Now, the ride is more controlled with greater absorption of the small road imperfections whilst maintaining impressive levels of waft.

There has been a significant reduction of "pothole explosions", maybe 30-40% better than before, but bearing in mind I am on 19" 225/35 and 255/30 I think it is fair play now.

However, I have noticed when going over speed bumps I get a boxy rattle every time (before and after changing shocks), so I am thinking whether this rattle is participating in the "pothole explosions"?

There are not many bad potholes in my local area...I have only experienced "pothole explosions" on maybe 2 or 3 specific streets. I drove over one of those streets after the new shocks and the "pothole explosion" was more of a loud thud rather than a loud bang like before.

Ok guys, an update.

When I got the front shocks installed, As I mentioned above, the ride became more controlled.

However, over the weekend I had a look under the bonnet to makesure the mounts were installed correctly in terms of the alignment pin. What I found was shocking....Both mounts were installed incorrectly as the alignment pin was not sitting in the hole, but actually protruding through the sheet metal near the front stud as a dent due to the 3 studs being tightened hence forcing the pin to dent through the sheetmetal!!

I then got my handy endoscope phone camera (7.99 off amazon and a must have!) and could actually see the alignment pin hidden under the sheetmetal.

Due to this incorrect installation, the mount were not sitting flush hence the ride felt more 'controlled' which I have to admit was more towards the firm side hence more road imperfections were being "noticed" belt felt better absorbed than before.

So, I thought, this may be affecting the ride comfort...so I called the garage, they said yes it has been installed wrong if the pin is not in its hole.

Got the car back yesterday and now the pins are in their holes AND I completely shocked and amazed at the ride now.

Much less noise over those sharp imperfections, much much more smooth, the waft actually feels more silky hence the seats feel more comfortable now. The front end of the car feels more confident over the first encounter with bumps. Wow, it has transformed the car and I am no longer regretting the 19" wheels and low profile tyres the car came with!

Not been over a pothole yet, but I have been driving the car since yesterday (when the mounts were installed correctly) and we have some very bad roads here in the UK and I am completely amazed at the ride...It feels like a different car...like I have downgraded to 17" rims with high profile tyres! The normal bangs and thuds I used to get in the car before are actually very well damped and quiter now.

After this experience, I can't admit that the BMW E9x SE suspension is under-damped...actually the opposite for me. Okay, the pothole explosions may still be there, but I am confident they will be quieter now and I don't mind the sacrifice of pothole explosions when the car drives this impressive.

I would definitely recommend SACHS oem-spec suspension as they have transformed the car. Mine has 19" rims and if the car provides this impressive level of comfort (IMO) it should offer even more comfort for those of you with 18" or lower rim sizes on a SE trim.

Originally Posted by bmw_solid

After this experience, I can't admit that the BMW E9x SE suspension is under-damped...actually the opposite for me.

That's because the dampers are fresh...the car drove the same exact way when it was new, so nothing you are noticing is that surprising. The problems will start again as they begin to wear and you'll eventually get back to the same conditions you experienced before.

In your case, I hope that doesn't happen for a while, at least.

[bmw_solid]

Originally Posted by FCobra94

That's because the dampers are fresh...the car drove the same exact way when it was knew, so nothing you are noticing is that surprising. The problems will start again as they begin to wear and you'll eventually get back to the same conditions you experienced before.

In your case, I hope that doesn't happen for a while, at least.

Hope for the best, fingers crossed

[bmw_solid]

However, just noticed yesterday that the suspension is now behaving like before...loud bangs and clunks and interior noises...

Opened the bonnet and had a look at the strut mounts and I noticed that the driver's side strut mount is sitting lower than the passenger side because the alignment pin is maybe 2-3mm lower than the alignment pin on the passenger side.

Clearly my mechanic hasn't done a good job.

I would like to know, can I simply tighten the 3 strut mount nuts with the wheel off and the lower arm supported by a jack to mimic under load condition or can I tighten those 3 nuts with the wheel on the car?

I was looking at newTIS and the torque spec for those 3 nuts is 35 Nm but that can only be applied when installing the strut+spring back into the car without and of the arms and steering rod connected to it...

Any thoughts?

Sounds fuct...take it to a competent shop.

[bmw_solid]

Originally Posted by FCobra94

Sounds fuct...take it to a competent shop.

I know....I was just wondering if I could tighten it again with the suspension loaded... there is a BMW specialist local to me so I might pay a visit to them.


Also, my car is in dire need of tracking but the track rod ends and rear toe arm bolts have seized, hence I am in a bit of a pile of mess with regards to that also.

Thanks.