[bmw335ie90]

Currently have whiteline subframe inserts and need more, the rear end is still sloppy over bumps. Four options I've found:

1. OEM M3 Bushing - I don't even know if these will give me a noticeable increase in rigidity over the inserts currently installed
2. Poly - Potential to squeak and deformation over time
3. Delrin - difficult (impossible?) to find for non-M
4. Aluminum - Difficult to install, whole subframe needs to come out, NVH

I've read the numerous threads reviewing various subframe bushing replacements. Almost all of them are initial impressions, which of course are usually going to be positive, you have to feel validated to a certain extent when doing a mod to your car.

Any regrets? Long term issues? Wish you would have gone stiffer? Wish you would have gone less stiff?

[Torgus]

Solid aluminum. Zero nvh. Do it once and do it right. New Ms come with solid from the factory. M3 bushing is worthless and a waste of your time. Zero regrets. While in there there is stuff to do. The middle brake lines, good time to change rsb assuming you want to, rear diff bushings and I guess anything else read end related.

But seriously no one regrets solid rear subframe bushings. No nvh. The stock and m3 bushings can't handle putting power down. Especially in an n54 powered vehicle.

Just to be clear being sloppy over bumps could be your spring and struts etc.

What is your rear suspension set up now?

I would probably do delving diff bushings as I hear they do not give diff whine. Lockdown kit is also an option.

[bmw335ie90]

Originally Posted by Torgus

Solid aluminum. Zero nvh. Do it once and do it right. New Ms come with solid from the factory. M3 bushing is worthless and a waste of your time. Zero regrets. While in there there is stuff to do. The middle brake lines, good time to change rsb assuming you want to, rear diff bushings and I guess anything else read end related.

But seriously no one regrets solid rear subframe bushings. No nvh. The stock and m3 bushings can't handle putting power down. Especially in an n54 powered vehicle.

Just to be clear being sloppy over bumps could be your spring and struts etc.

What is your rear suspension set up now?

I would probably do delving diff bushings as I hear they do not give diff whine. Lockdown kit is also an option.

Thanks for the feedback! I have M performance yellow springs and koni yellow shocks with about 10k miles on them. When I bought the car with 45k miles totally stock the tail felt super sloppy, inserts helped quite a bit but it still was nowhere near as tight as my e39 that had 150k miles and all original rear suspension bushings.

For me there is no need for diff lockdown as I don't have issues with wheel hop but I might do Mfactory solid rubber diff bushings while in there. Rarely ever do pulls from a stop, just want the wishy washy tail to go away.

Funny you mention the middle brake lines as I have a set sitting in my garage. I bought the full set and replaced front and rear but then realized it was going to be way too much effort to do the middle ones without lowering the subframe.

I just really wonder why BMW engineers did not use solid bushings in the e90 M3 if there is not any increase in NVH.

[thakid22]

Originally Posted by bmw335ie90

Currently have whiteline subframe inserts and need more, the rear end is still sloppy over bumps. Four options I've found:

1. OEM M3 Bushing - I don't even know if these will give me a noticeable increase in rigidity over the inserts currently installed
2. Poly - Potential to squeak and deformation over time
3. Delrin - difficult (impossible?) to find for non-M
4. Aluminum - Difficult to install, whole subframe needs to come out, NVH

I've read the numerous threads reviewing various subframe bushing replacements. Almost all of them are initial impressions, which of course are usually going to be positive, you have to feel validated to a certain extent when doing a mod to your car.

Any regrets? Long term issues? Wish you would have gone stiffer? Wish you would have gone less stiff?

What are you trying to improve on your car? You mention that the rear is "sloppy." There are all kinds of ways that could be interpreted. We need specifics to know what direction to point you in...
What is the car doing that it shouldn't be doing? What is it not doing that it should be doing? What inputs/outputs aren't matching up to your liking? Answer these questions and we can help you fix your slop.

If the rear of the car is sloppily bouncing up and down, then check out my thread here: https://www.e90post.com/forums/showthread.php?t=1024256
A set of $99 Dinan upper rear strut mounts will fix that and give you a bit more wheel travel. The ride becomes smoother and more well controlled.
No NVH penalty.
Monroe makes a set of mounts for about $20 that tighten up the rear, but don't add any wheel travel. Go for the Dinans though, I loved them and can vouch for them.

The other sloppiness found on E90's come in the form of the rear end skipping sideways on corners over potholes and bumps. This is usually alignment/tire wear/ and bushing wear related. Have a look around back there and see which applies to you.

If you are on Factory rear strut mounts, replace those no matter what. The Dinan units are much better. You won't believe the difference. The stock ones are too soft foam designed to help reduce harshness from the OEM runflat tires. They are borderline too soft when new. But any aging or wear dramatically skews them toward even more soft.

[bmw335ie90]

Originally Posted by thakid22

What are you trying to improve on your car? You mention that the rear is "sloppy." There are all kinds of ways that could be interpreted. We need specifics to know what direction to point you in...
What is the car doing that it shouldn't be doing? What is it not doing that it should be doing? What inputs/outputs aren't matching up to your liking? Answer these questions and we can help you fix your slop.

If the rear of the car is sloppily bouncing up and down, then check out my thread here: https://www.e90post.com/forums/showthread.php?t=1024256
A set of $99 Dinan upper rear strut mounts will fix that and give you a bit more wheel travel. The ride becomes smoother and more well controlled.
No NVH penalty.
Monroe makes a set of mounts for about $20 that tighten up the rear, but don't add any wheel travel. Go for the Dinans though, I loved them and can vouch for them.

The other sloppiness found on E90's come in the form of the rear end skipping sideways on corners over potholes and bumps. This is usually alignment/tire wear/ and bushing wear related. Have a look around back there and see which applies to you.

If you are on Factory rear strut mounts, replace those no matter what. The Dinan units are much better. You won't believe the difference. The stock ones are too soft foam designed to help reduce harshness from the OEM runflat tires. They are borderline too soft when new. But any aging or wear dramatically skews them toward even more soft.

More good info thank you!

My car has 65k miles on it currently with 10,000 miles on new M3 front control arms, Koni yellows, m perf yellow springs. When I did this upgrade I also replaced the rear spring pads, lower shock mount, front strut top mount etc. Basically everything that's connect to shock, spring, strut. Also I have already installed the Dinan rear upper shock mounts when I did the suspension upgrade but these did not offer me any noticeable improvement in rear end 'togetherness' but I appreciate the advice. Planning to do Dinan fixed front camber plates and E93 M3 front sway bar soon. I know after I do more to the front suspension the rear is going to feel even worse.

Running 255 Pilot Super Sports on all four tires with -1.2 front camber and -1.8 rear camber and around 0.10-0.15 toe. Alignment and tires are the best I can get with current setup. Grip is phenomenal but body roll and this loosey goosey back end are the next targets for me which leads me to the Rear Subframe Bushings.

The back end 'slop' I notice is basically when you hit a rough patch of road the car feels likes its going one direction and the back end feels like its going the opposite. Feels like a rubber band and is very sketchy when deep into throttle coming out of a corner and you hit a bad patch of road.

[Torgus]

yeah the loosey goosey spongey rear firms right up with the subframe bushings. Everyone should do the mod IMO. It's just a hassle so most don't. The parts are cheap all things considered.