Solid subframe bushings

[Pitkis]

Originally Posted by aajami

Malek is correct. The bushings are literally welded onto the subframe of the CRT and GTS, so they cannot be purchased separately. This is the same subframe and bushing combination used on the GT4, which costs about $2,200.

So you can buy "solid rear" from BMW M and install it to your E92 DD? Does it fit, anybody knows? It's not even more much than group N bushing at USD 800.

[tibra1]

Has anyone considered that that the M5's entire suspension was designed to incorporate a solid subframe such as this..trying to apply a 1 to 1 ...to the M3 would not be optimal ..completely apples and oranges

[aajami]

Originally Posted by tibra1

Has anyone considered that that the M5's entire suspension was designed to incorporate a solid subframe such as this..trying to apply a 1 to 1 ...to the M3 would not be optimal ..completely apples and oranges

For what it's worth, the GT4 has different suspension than the GTS/CRT, and yet they share the same rigid subframe.

[bigjae1976]

I think BMW has had a continual problem with their rear floors holding together. I'm sure the E46 class action lawsuit stung a bit. Paying to fix a bunch of old cars of the 2nd or 3rd owner...who BMW probably made no money off of. You also have to look at the increase in HP amd vehicle weights over the years. The F10 M5 puts down 500+ hp & torque and weighs about 4250 lbs! I'm thinking that BMW figured rubber would wear out pretty fast. So stepping up to solid bushings make sense.

The whole PIA about this is that its hard to check the subframe bushings if you can even check them without removing the subframe. On my E46 I took the approach which is easier to replace? diff bushings or subframe bushings? So I've went with poly subframe bushings (should have went solid) and OEM diff bushings. At least I can see the diff bushings and I don't have to drop and disassemble the entire rear end to replace them.

Of course, this discussion is pointless for someone who doesn't plan on keeping their car. Me? I'm installing the solid subframe mounts when I'm out of warranty.

[e92zero]

It looks like replacing the subframe bushing to solid one is good way to go with no impact to NVH. I will probably go that route later on as I plan to keep this car for as long as I can.

However this worries me.

Originally Posted by italyix

100% agree with this. My diff bushings are noisy...a constant whine, sounds like a motor winding up and down.

I don't want the wind as it's my dd and others in the family would not appreciate it one bit. From italyix's thread, it's the foam diff bushing in the back that worries me the most. Would be nice if we can source a harder rubber one or the group N one to replace this foam piece. I saw on turner's page that they do have a harder rubber diff bushings for the older generation. Not sure when/if they will come out with one for our E9X.

[Malek@MRF]

Originally Posted by Pitkis

So you can buy "solid rear" from BMW M and install it to your E92 DD? Does it fit, anybody knows? It's not even more much than group N bushing at USD 800.

Yes it is a complete bolt on piece. You can literally purchase this subframe, transfer all your links, arms and other parts over and begin to put it back together.

The improvement is drastic.

[Malek@MRF]

Originally Posted by tibra1

Has anyone considered that that the M5's entire suspension was designed to incorporate a solid subframe such as this..trying to apply a 1 to 1 ...to the M3 would not be optimal ..completely apples and oranges

I couldn't disagree more in this regard.

BMW like any other great company learns and progresses over time. They learn from previous designs and their implications.

There is no harm in changing the rubber sub-frame bushings to solid. By harm, I am referring to physical harm to the vehicles chassis and its dynamics. I am not referring to harm caused in potential ride comfort reduction (which is extremely subjective in most cases).

A rigid sub-frame reduces, if not prevents sub-frame and in worse cases, uni-body damage (as evident in E36 and E46 cars).

If one was to unitize other parts, such as the differential to the axle carrier, yes other work will need to be done, such as reinforcement to the mounting brackets and tabs. It is not true that if you unitize the differential it will prevent this, the load and shock of the differential are now being transferred to the next weakest link, the differential mounts themselves.

If you undo the sub-frame out of the E9x M3, you will see how unimpressive the differential mounts are. Changing these bushings will now reduce the failure of hardware and the actual bushing at the cost of the mounts. Energy is never lost, only transferred.

[italyix]

Originally Posted by e92zero

It looks like replacing the subframe bushing to solid one is good way to go with no impact to NVH. I will probably go that route later on as I plan to keep this car for as long as I can.

However this worries me.


I don't want the wind as it's my dd and others in the family would not appreciate it one bit. From italyix's thread, it's the foam diff bushing in the back that worries me the most. Would be nice if we can source a harder rubber one or the group N one to replace this foam piece. I saw on turner's page that they do have a harder rubber diff bushings for the older generation. Not sure when/if they will come out with one for our E9X.

I'd be glad to give you a ride and you can hear for yourself. I agree though, NOT a family friendly mod...for sure

[Pitkis]

Originally Posted by Malek@MRF

Yes it is a complete bolt on piece. You can literally purchase this subframe, transfer all your links, arms and other parts over and begin to put it back together.

The improvement is drastic.

I leafed through drawings of ordinary & GT4 rear subframe and could not find a single difference between them. Bushing is naturally different, but that's it? Maybe a slight reinforcement somewhere but not in a scale that can be seen in drawings?

[e92zero]

Originally Posted by italyix

I'd be glad to give you a ride and you can hear for yourself. I agree though, NOT a family friendly mod...for sure

Thanks for the generous offer. I will definitely take you up on that. pm on the way.

[Tuner1]

Updates? Have any E9X owners installed solid rear subframe bushings yet?

I am not interested in solid diff mounts/bushings.

My experience with very stiff or solid rear subframe bushings on other models of cars are exactly what Malek posted below - no perceived increase in NVH.

Originally Posted by Malek@MRF

The M3 GTS and CRT both utilize the same subframe. Also, they do not have separable bushings. The subframe is simply designed as a solid mounting piece.

Think of it as the bushings being welded in.

I will also reiterate this, having solid sub-frame bushings will NOT degrade ride quality. This is what happens with solid driveline bushings (motor, transmission, differential).

On another BMW forum HP Autowerks said

We have done many of these mods with solid alum. bushings from Turner Motorsports. This is a mod that is strictly reserved for track cars. Unless you like the whole car to buzz all you and feel everything on the road we recommend the M3 bushings over the delrin or alum.

Maybe HP is referring to installing solid subframe and solid diff bushings at the same time. I have a hard time believing that BMW would product two top-tier products (M3 GTS and CRT) with severe NVH issues.

[italyix]

Originally Posted by Tuner1

Updates? Have any E9X owners installed solid rear subframe bushings yet?

I am not interested in solid diff mounts/bushings.

My experience with very stiff or solid rear subframe bushings on other models of cars are exactly what Malek posted below - no perceived increase in NVH.

On another BMW forum HP Autowerks said

Maybe HP is referring to installing solid subframe and solid diff bushings at the same time. I have a hard time believing that BMW would product two top-tier products (M3 GTS and CRT) with severe NVH issues.

I have both solid subframe bushings and diff bushings from TMS. Been running them for a while now and I wrote a review on them as well. I do not mind the NVH produced. I don't notice it anymore and I DD my car in traffic.

[Tuner1]

Originally Posted by italyix

I have both solid subframe bushings and diff bushings from TMS. Been running them for a while now and I wrote a review on them as well. I do not mind the NVH produced. I don't notice it anymore and I DD my car in traffic.

I just found your review.

TMS Subframe Bushings
These tie the rear suspension components nicely to the subframe. As you can see, the stock ones are rubber and are stamped with the M logo. No discernible difference from rubber to delrin with regards to NVH.

My only question is....if you did the TMS solid subframe and diff mounts at the same time how can you be sure that the subframe mounts added "No discernible difference from rubber to delrin with regards to NVH."?
Maybe I didn't understand your post correctly and the upgrades were done in stages?

[italyix]

Originally Posted by Tuner1

I just found your review.



My only question is....if you did the TMS solid subframe and diff mounts at the same time how can you be sure that the subframe mounts added "No discernible difference from rubber to delrin with regards to NVH."?
Maybe I didn't understand your post correctly and the upgrades were done in stages?

The upgrades were done together. The biggest contributor to noise were the diff bushings, as they do not muffle the whining of the diff gears, and the noise is directly transmitted into the rear of the cabin. From my review, I did not notice any increase in NVH from the subframe bushings. It might be because the noise is blended among the other upgrades, or there might no be any noise at all from the subframe bushings.

The noise has died down quite a bit since the upgrades were done. It might also be I have gotten used to it but I can still hold a conversation at normal voice level.

[klammer]

I've done the TMS delrin subframe mounts along with the dinan monoball and R&D sport sways after having my car setup the same for over a year and can tell you the subframe mounts did very little if anything to NVH. Car felt tighter, more communicative all around (monoball definitely helped the front end) and could sense more of what the car wanted to do, at the limit of course. Going over speed bumps there's a bit of a squeak, but other than that, cars quiet and just feels more like 1 solid piece now than before. I love it, my wife hasn't noticed a thing, and would recommend it to anybody who wants a bit of a "tighter" car/ride. Hope that helps

[Tuner1]

Originally Posted by klammer

I've done the TMS delrin mounts along with the dinan monoball and R&D sport sways after having my car setup the same for over a year and can tell you the subframe mounts did very little if anything to NVH.

Thanks for the feedback. So you don't hear any whining from the diff at steady-state cruise or under decal? No added vibration under WOT?

[klammer]

Originally Posted by Tuner1

Thanks for the feedback. So you don't hear any whining from the diff at steady-state cruise or under decal? No added vibration under WOT?

Oops, edited my post, it was the subframe, not the diff, that I replaced. Noticed very little NVH but appreciate the added response and feel

[italyix]

Originally Posted by klammer

I've done the TMS delrin subframe mounts along with the dinan monoball and R&D sport sways after having my car setup the same for over a year and can tell you the subframe mounts did very little if anything to NVH. Car felt tighter, more communicative all around (monoball definitely helped the front end) and could sense more of what the car wanted to do, at the limit of course. Going over speed bumps there's a bit of a squeak, but other than that, cars quiet and just feels more like 1 solid piece now than before. I love it, my wife hasn't noticed a thing, and would recommend it to anybody who wants a bit of a "tighter" car/ride. Hope that helps

Klammer, thank you. I too get a squeak over speed bumps. And yes, the car does feel tighter and more connected to the suspension, I'm glad it was not just in my head

I gotta try the dinan monoball...perhaps next year.