[bmw_solid]

Hi All,

Hope you are all well.

I have attached a screenshot from realoem below of the arms at the left and right side of the rear axle (realoem link provided below).

Car: E92 330d SE Pre LCI 107,000 miles with New x4 oem SACHS shocks and mounts and bump stops + New Febi control arm and wishbone at the front left and right.

Symptoms: Car now drives much better than before, however, the bumps at the rear feel a bit too firm and sound a bit noisy/thudy also. + Quite a lot of road noise on some surfaces (all 4 tyres balanced, tracking is due as i'm awaiting for new rack rods)

I would like to know:

1) which of the 4 arms at the rear wheel (19, 18, 14 or 4) contribute to a comfortable ride at the rear when going over bumps?

2) which of the 4 arms at the rear wheel (19, 19, 14 or 4) contribute to insulation of road noise/vibration?

I have inspected all the bushings for the 4 arms on both sides and found the below:

Part #19 (33322409890) has really bad bushings (cracked/missing rubber and rust formation) on the sub frame side and quite bad bushings on the wheel side.

Part #18 (33322406292) has slightly perished bushings on the wheel side (sub frame side are okay)

Part #14 (33322406290) has okay bushings on both sides

Part #4 (33326772899) has rusted bushings on the sub frame side and okay bushings on the wheel side.

Hoping someone can let me know ultimately which of the rear arms could be a culprit of deprived comfort at the rear and which of the 4 arms could cause a excessive tyre noise/vibration to enter cabin.

Thanks for reading.

https://www.realoem.com/bmw/enUS/sho...diagId=33_1230

[bmw_solid]

As far as tracking/wheel alignment is concerned, I know that all 4 wheels are off alignment. I am hoping after all 4 wheels are aligned, the tyre noise/vibration would decrease significantly, but if it doesn't then the next only reason could be a bad bushing on one of the arms... no run flats on my car either.

[bmw_solid]

Bump

[Phil325i]

Unless one of your bushings is actually rusted solid, IMHO the greatest influence on ride quality is spring rate and damper type. You say the ride is 'thuddy' - but compared to what? The E9X is not known for magic carpet ride quality. It's one reason I paid a lot of money for Ohlins springs and dampers to transform the ride quality while still ensuring excellent handling. You pays your money...

[bmw_solid]

Originally Posted by Phil325i

Unless one of your bushings is actually rusted solid, IMHO the greatest influence on ride quality is spring rate and damper type. You say the ride is 'thuddy' - but compared to what? The E9X is not known for magic carpet ride quality. It's one reason I paid a lot of money for Ohlins springs and dampers to transform the ride quality while still ensuring excellent handling. You pays your money...

The rubber on the bushing of control arm 19 is completely shot.

I just recently had new front control arms and track control arms fitted, febi parts, and the amount of difference they made was actually more noticeable/appreciable than when I had the new shocks fitted. A more controlled waft and much much less bangs and thuds over bumps/large imperfections.

I don't really have any complaints for the overall comfort, just this feeling of a firm rear end compared to the front of the car.

Its like the bushings on one of the control arms is completely gone from inside and is not letting the rear shocks absorb the bump properly hence giving that 'firm' feel at the back.

If I can find out which of those 4 arms are the major contributor to comfort, I cam simply make a call whether to replace that arm or not depending on my visual inspection of the bushings.

I'm hoping it is control arm 19 as the bushings on that look really bad from outside (no rust but perished/dislocated rubber).

[Phil325i]

A good BMW Indy tech with a crowbar or wobble play detector should be able to tell where the play is in your bushings...

[bmw_solid]

Originally Posted by Phil325i

A good BMW Indy tech with a crowbar or wobble play detector should be able to tell where the play is in your bushings...

You mention the word 'good' but some of these 'indys' are far than good

We use our local Mercedes Indy and actually end up suggesting them what to do after learning on the forums and actually fixing our problems ourselves.

My local BMW indy said my car drove perfectly fine when I was complaining about a slightly sharp ride due to a upside-down washer in the front left strut mount. After getting the washer correctly installed, the ride transformed to a comfortable ride.

So how accurate indys can be is a big question mark for me

I might the bite the bullet and buy 2 new febi controls arms part #19 hoping that I wont need to get my tracking done again (booked for later this week) after installing them

[pizza_nightmare]

Any updates on your progress? Why not just change all the bushings and rubber bits and be done with it, or is this just genuine curiosity? Or if the rear is rusted out, buy a replacement kit like FCP Euro's multipiece control arm kit?

[bluewater328]

If the rear is "just firm" then how about some Dinan (or other) rear upper shock mount kit. I think Turner makes a decent one as well. Allows your shock to travel farther, so you may get a little more comfort out of it.

[Mark963]

I think I'm in the same boat and there are some misunderstandings. Mine will sail over a "rain curb" that goes up a couple of inches over a couple of inches of forward travel with no trouble. In fact, it's kind of Lexus-ish that way and surprises me with how gentle it is. Mine is an X drive, so no real sport suspension, just 17" wheels. So I don't think the issue has anything to do with the springs or bump stops.

Little steps in the seams just going down the street - maybe 1/2" or something like that - clearly not causing a big suspension movement, but some - will sound like someone just hit the trunk area with 10 pound rubber mallet. It's more of bang than a thud and it seems totally out of place with little the car actually goes up or down. On what looks like a nice street, I hit a couple every minute. It's not THAT horrible, but everything in the car vibrates with it and its a few steps above noticeable.

So I'm thinking the same thing as the OP. That two or three of these dozens of bushings are shot and there's play in them and that makes the suspension buckle or move too easily and then suddenly come to the end of that slop and BANG. But I'm pretty amateur at figuring what suspension components are worn.

I bought 10 year old car, but I don't want it to feel 10 years old and I'm willing to spruce it up if I knew how. I guess I need to get it back up in the air and just try poking around everything with a pry bar and just see what I find.

[Phil325i]

Originally Posted by bmw_solid

You mention the word 'good' but some of these 'indys' are far than good

There are good and bad apples in every barrel. I'm clearly fortunate to have an indy I'd trust with my life...

[gjm120]

Originally Posted by bmw_solid

The rubber on the bushing of control arm 19 is completely shot.

I just recently had new front control arms and track control arms fitted, febi parts, and the amount of difference they made was actually more noticeable/appreciable than when I had the new shocks fitted. A more controlled waft and much much less bangs and thuds over bumps/large imperfections.

I don't really have any complaints for the overall comfort, just this feeling of a firm rear end compared to the front of the car.

Its like the bushings on one of the control arms is completely gone from inside and is not letting the rear shocks absorb the bump properly hence giving that 'firm' feel at the back.

If I can find out which of those 4 arms are the major contributor to comfort, I cam simply make a call whether to replace that arm or not depending on my visual inspection of the bushings.

I'm hoping it is control arm 19 as the bushings on that look really bad from outside (no rust but perished/dislocated rubber).

Changing out #19 guide rod to "M" arms actually results in a lowering of spring rate. Read the op in this thread, particularly the bottom paragraphs.

https://www.1addicts.com/forums/show....php?t=1079383

[bmw_solid]

Sorry everyone for not replying as for some reason I didn't subscribe myself to this thread. Replies to follow now:

[bmw_solid]

Originally Posted by pizza_nightmare

Any updates on your progress? Why not just change all the bushings and rubber bits and be done with it, or is this just genuine curiosity? Or if the rear is rusted out, buy a replacement kit like FCP Euro's multipiece control arm kit?

No further work done so far to the rear. I tried to get the tracking done at 4 different places and all of them said the rear cambers and toe arm bolts have seized and can't be opened.

So atm, I am not bothering with tracking as I know I will need new camber and toe arms which will be pretty costly.

I could change all 8 (?) bushings but that will be very labour intensive I understand so better to change the arms as the new arms come with new bushing built in.

[bmw_solid]

Originally Posted by bluewater328

If the rear is "just firm" then how about some Dinan (or other) rear upper shock mount kit. I think Turner makes a decent one as well. Allows your shock to travel farther, so you may get a little more comfort out of it.

Hmmm, I wasn't aware of this kit... but would't further travel affect the handling characteristics of the car?

Tbh, I think it is down the the arms having worn bushings. I am sure, If I changed all 4 arms now, the rear comfort would transform as I have new shocks so doing all 4 arms would result to a complete rear suspension overhaul.

However, my main aim from this thread was to discover which of the 4 arms contribute to comfort and simply replace those, hoping it would e the toe and camber arms as the bolts are seized on these and replacing these would then suit me for 2 purposes: 1) more comfort and 2) allow me to get my tracking done

[bmw_solid]

Originally Posted by Mark963

I think I'm in the same boat and there are some misunderstandings. Mine will sail over a "rain curb" that goes up a couple of inches over a couple of inches of forward travel with no trouble. In fact, it's kind of Lexus-ish that way and surprises me with how gentle it is. Mine is an X drive, so no real sport suspension, just 17" wheels. So I don't think the issue has anything to do with the springs or bump stops.

Little steps in the seams just going down the street - maybe 1/2" or something like that - clearly not causing a big suspension movement, but some - will sound like someone just hit the trunk area with 10 pound rubber mallet. It's more of bang than a thud and it seems totally out of place with little the car actually goes up or down. On what looks like a nice street, I hit a couple every minute. It's not THAT horrible, but everything in the car vibrates with it and its a few steps above noticeable.

So I'm thinking the same thing as the OP. That two or three of these dozens of bushings are shot and there's play in them and that makes the suspension buckle or move too easily and then suddenly come to the end of that slop and BANG. But I'm pretty amateur at figuring what suspension components are worn.

I bought 10 year old car, but I don't want it to feel 10 years old and I'm willing to spruce it up if I knew how. I guess I need to get it back up in the air and just try poking around everything with a pry bar and just see what I find.

You see there are 3 possibilities here by changing the arms:

1) If you change all the 4 arms or the 'offending/worn' arms you will eliminate the thuds/bangs completely and also improve the comfort.

2) You change all the 4 arms or the 'offending/worn' arms and will maybe eliminate 60-70% f the thuds/bangs and improve the comfort

3) You change all the 4 arms or the 'offending/worn' arms and will not notice any or much difference.

The reason I think the above are possible is becuase the E9x generation (excluding the M3) apparently have poorly designed shock absorbers by the engineers at BMW as there is a widely known symptom called 'pothole explosions' on this forum (and others) due to the poorly designed shocks.

Personally, I think that if all 4 arms were changed it would result to possibility No. 2 as the factory suspension is flawed therefore meant to produce those loud thuds/bangs compared to the rival cars of the E9x.

I changed all 4 shocks on my car to OEM Sachs shocks + Lemforder front mounts, Febi Rear Mounts and I also changed both arms on the front with Febi arms as the arms were shot completely.

After changing the front arms, I basically have a complete new front suspension all to OEM SE trim level spec (my car is a SE). If i compare the before and after, it is like this: When I changed the shocks, the car had developed more waft/float and ride was more comfortable. However, those thuds/bangs were still there but noticeably less. After about 2 months, I then changed the front arms and thats when the thuds/bangs (at the front) disappeared 60-70%. It completely transformed the car to a much more appreciable level...a level that I can live with and understand as the factory suspension design is flawed after all.

So, I think if the arms at the rear were changed, It will eliminate those thuds/bangs to a appreciable level, I believe from my experience.

[bmw_solid]

Originally Posted by gjm120

Changing out #19 guide rod to "M" arms actually results in a lowering of spring rate. Read the op in this thread, particularly the bottom paragraphs.

https://www.1addicts.com/forums/show....php?t=1079383

Interesting, I will take a read of that thread properly when I have some spare time. Thanks.

[feuer]

Originally Posted by bmw_solid

You mention the word 'good' but some of these 'indys' are far than good

We use our local Mercedes Indy and actually end up suggesting them what to do after learning on the forums and actually fixing our problems ourselves.

My local BMW indy said my car drove perfectly fine when I was complaining about a slightly sharp ride due to a upside-down washer in the front left strut mount. After getting the washer correctly installed, the ride transformed to a comfortable ride.

So how accurate indys can be is a big question mark for me

I might the bite the bullet and buy 2 new febi controls arms part #19 hoping that I wont need to get my tracking done again (booked for later this week) after installing them

Respectfully, any indy would know more than you about cars in general as you only know about your car. You just need to find Indy that care about you as a customer.

[bmw_solid]

Originally Posted by feuer

Respectfully, any indy would know more than you about cars in general as you only know about your car. You just need to find Indy that care about you as a customer.

Yes that is correct but not always the case as when my dad took his S-Class to our local Mercedes indy to diagnose a starter battery issue and ended up paying £550 but still not fixing the problem... I then contacted a member on a Mercedes forum and he kindly sent the circuit wiring diagrams as PDFs and explained some of the key components and layouts as he was a Electrical engineer.

After taking his advice, we did some simple continuity checks and found the issue and simply ran a new wire from the pre-fuse box to the power supply module and sorted the problem out ourselves for under £5!

I can give many more examples of when we have taken our cars, both BMW and MBs to our local indys and given the usual answer "they do that" or "they are all like that" or "its very common, I wouldn't bother".

Maybe the indys in your area/state are more skilled or passionate about cars but in my area I haven't really come across many 'passionate' indys, or it could be that they get so busy and work on the same cars again and again, they sort of leave behind that passion and take it as usual business.

[The Nightman]

On the topic of ride comfort, what are your tire specs and what pressures are you running? If your tires have a different load rating than stock, you should adjust them to match the factory load ratings. It's common that replacement tires with a higher load rating are over-inflated.

[bmw_solid]

Originally Posted by freedomfries

On the topic of ride comfort, what are your tire specs and what pressures are you running? If your tires have a different load rating than stock, you should adjust them to match the factory load ratings. It's common that replacement tires with a higher load rating are over-inflated.

I currently have non-run flats tyres which are all factory spec:

Fronts: 225/35/R19
Rears: 255/30/R19

Its worth mentioning that they are decent budget brands...rears are Rotalla and fronts I can't remeber but obviously not really great tyres...

The wheels are LA Star (?), just for reference.

I'm running the stock pressure values shown on the data card on the door jam area. I think it 2.6 PSI on the front and 2.8 PSI on the rear...these are the values for 2 passengers as very rarely there are more than 2 people in the car together.

I do not know much about the load rating... I will check this on the tyres tomorrow. However, where can the factory load ratings be found? If the tyres load ratings are different to factory specs, how can match them to the factory spec?

Thanks.

[The Nightman]

You can find the factory load ratings in the tire pressure specifications of the owner's manual. I believe the factory 19" tires are 225/35R19 88Y XL and 255/30R19 91Y XL. It's likely your tires have the same load rating though so no adjustment may be required.

If your tires have a different load rating, use a load inflation table and find each tire's load capacity by looking up the tire's load rating and the specified pressure. Then look up the load rating of your new tires and find which pressure matches/exceeds the load capacity.

Load inflation table (see pages 28-31 for metric standard and reinforced loads): https://www.toyotires.ca/sites/defau...s_20170203.pdf