Solid subframe bushings

[buddyguypal]

Originally Posted by italyix

YES! Expect it tonight on my original thread. I still need to snap a few pics of the bushings that came out, then I will write a full review of all the parts installed.

waiting anxiously

[klammer]

Originally Posted by Lights407

waiting anxiously

Me too. I am getting these installed in about 2 weeks.

[e92zero]

Anyone planning to just install the diff bushings? Member tres mentioned that he installed the diff bushings and there is no increase in NVH. However, member italyix mentioned that the diff bushings is really bad in increased NVH. But italyix also install the subframe bushing at the same time. Want to see if there is a clear result on which bushings increase NVH the most.

[Autobahn335i]

Originally Posted by e92zero

Anyone planning to just install the diff bushings? Member tres mentioned that he installed the diff bushings and there is no increase in NVH. However, member italyix mentioned that the diff bushings is really bad in increased NVH. But italyix also install the subframe bushing at the same time. Want to see if there is a clear result on which bushings increase NVH the most.

I've replaced the rear diff bushing (the big one) with a Powerflex polyutherane bushing on my 335i 6AT. There IS a slight increase in NVH. Gear whine is transmitted into the cabin, notably in the 3k rpm range. It's really not bad but definitely noticeable. So I suspect you would experience similar things on the M3.

Looking forward to the updates after the subframe bushings installations

[italyix]

Originally Posted by e92zero

Anyone planning to just install the diff bushings? Member tres mentioned that he installed the diff bushings and there is no increase in NVH. However, member italyix mentioned that the diff bushings is really bad in increased NVH. But italyix also install the subframe bushing at the same time. Want to see if there is a clear result on which bushings increase NVH the most.

The meshing noise created by the diff gears travels directly through the chassis and into the truck. The trunk is acting like a bass box and amplifying the noise. This could be attributed to the fact that yes, I have subframe bushings installed, therefor the noise travels from diff -> chassis -> bushings -> trunk.

[Z K]

I replaced subframe bushings before on a previous RWD car and I remember that made a big difference in how the car felt. It also didn't really add any NVH to the car besides the rear feeling firmer. But in that case I used polyurethane bushings so it isn't as firm as a solid replacement.

Are there any firmer but not fully solid bushings that can be used on the M3?

[cvc 22349a]

Originally Posted by Z K

I replaced subframe bushings before on a previous RWD car and I remember that made a big difference in how the car felt. It also didn't really add any NVH to the car besides the rear feeling firmer. But in that case I used polyurethane bushings so it isn't as firm as a solid replacement.

Are there any firmer but not fully solid bushings that can be used on the M3?

Yes. Powerflex polyurethane and BMW Motorsport group n.

[Tuner1]

Originally Posted by Malek@MRF

The GTS has solid mounts, so does the new M5 (a luxury sedan).

We have installed these at our shop and the increase in harshness is very little, Especially on street compliant suspension and tires.

Interesting...

I heard the GTS has solid subframe bushings (mounts) but have never seen a picture of them. I wonder if they are alloy, delrin or other? They are likely only available from BMW with the complete subframe.

Re the M5, does anyone have pictures of the solid mounts? I should get under a new M5 to see if BMW employed any tricks to tame the NVH when using the solid subframe mounts. Maybe liquid-filled diff mounts

IMO, any E9X M3 that is either driven hard and/or has more power than stock could really benefit from solid subframe mounts. My ESS VT2-625 kit made this issue far more obvious!

[bigjae1976]

I think BMW has said they use solid mounts in the M5. Don't think anyone is going to drop an F10 M5 subframe anytime soon though.

[e92zero]

Interesting. At this point, it seem pretty much confirmed that the M3 GTS uses solid subframe bushings. The question I have is if the GTS frame has extra reenforcement at the locations where the subframe is mounted to to handle the solid subframe bushings? I can't seem to find any solid evident/confirmation for this. Any one want to charm in? I don't want to change to solid/derin bushings and later down the road find fractures/cracks on the frame instead. Thanks in advance.

[Pitkis]

Originally Posted by cvc 22349a

Yes. Powerflex polyurethane and BMW Motorsport group n.

Powerflex doesn't supply E9x M3. Someone said that ordinary E9x versions fit E9x M3, but Powerflex states clearly that their E9x BMW bushing does NOT fit to M3.

[bigjae1976]

Originally Posted by e92zero

Interesting. At this point, it seem pretty much confirmed that the M3 GTS uses solid subframe bushings. The question I have is if the GTS frame has extra reenforcement at the locations where the subframe is mounted to to handle the solid subframe bushings? I can't seem to find any solid evident/confirmation for this. Any one want to charm in? I don't want to change to solid/derin bushings and later down the road find fractures/cracks on the frame instead. Thanks in advance.

I think solid mounts will eliminate the need for reinforcement. In the past, bad bushings cause more movement, more force when loading and unloading which is transmitted to the frame which eventually cracks.

[klammer]

Originally Posted by bigjae1976

I think solid mounts will eliminate the need for reinforcement. In the past, bad bushings cause more movement, more force when loading and unloading which is transmitted to the frame which eventually cracks.

These would be my thoughts as well...

[cvc 22349a]

Originally Posted by Pitkis

Powerflex doesn't supply E9x M3. Someone said that ordinary E9x versions fit E9x M3, but Powerflex states clearly that their E9x BMW bushing does NOT fit to M3.

OK. I didn't check; just assumed they're the same size. Poly wouldn't be my choice anyway. If I were to firm up my subframe mounts from M3, the Motorsport bushings would be my choice.

[aajami]

Originally Posted by Tuner1

Re the M5, does anyone have pictures of the solid mounts? I should get under a new M5 to see if BMW employed any tricks to tame the NVH when using the solid subframe mounts. Maybe liquid-filled diff mounts

Here you go:



Skip to 2:54.

I'll ask around about the GTS/CRT subframe mounts.

[Pitkis]

Originally Posted by cvc 22349a

OK. I didn't check; just assumed they're the same size. Poly wouldn't be my choice anyway. If I were to firm up my subframe mounts from M3, the Motorsport bushings would be my choice.

Dunno, this is pretty difficult. Metal is out, it's too hard without welding more reinforcement. Delrin is almost like metal; no go. Poly is hard and might work, but no one supply them. And Group N is rubber - racing rubber? How that is compared to OEM bushing? Any idea? Worth spending USD 800 to couple of bushes and find out that it's still rubber and far from hard plastics..?

[cvc 22349a]

Originally Posted by Pitkis

Dunno, this is pretty difficult. Metal is out, it's too hard without welding more reinforcement. Delrin is almost like metal; no go. Poly is hard and might work, but no one supply them. And Group N is rubber - racing rubber? How that is compared to OEM bushing? Any idea? Worth spending USD 800 to couple of bushes and find out that it's still rubber and far from hard plastics..?

Ask TurnerMS about the group n bushings. Solid alu or delrin are probably best for a strictly track car. If it's mostly a street car/occasional track, I'd go with the group n. For a DD, the oe M3 bushings are probably best. That's the feedback I've gotten from a couple engineers/tuners.

[italyix]

Originally Posted by cvc 22349a

Ask TurnerMS about the group n bushings. Solid alu or delrin are probably best for a strictly track car. If it's mostly a street car/occasional track, I'd go with the group n. For a DD, the oe M3 bushings are probably best. That's the feedback I've gotten from a couple engineers/tuners.

I have the delrin bushings and I can tell u the rear feels more planted and I DD the car.

The chassis feels more connected to the subframe.

[bigjae1976]

I think some poly or solid suspension bushings will not affect the ride comfort much. I wanna say the damper/spring relationship is the key to ride comfort. I might notice some more feel transmitted through the steering wheel with poly bushings. The squeaks might driving you crazy.

Driveline bushings will transmit a lot more NVH.

[italyix]

Originally Posted by bigjae1976

Driveline bushings will transmit a lot more NVH.

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

[Malek]

Originally Posted by aajami

Here you go:



Skip to 2:54.

I'll ask around about the GTS/CRT subframe mounts.

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).

[aajami]

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).

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.