Are rubber rear subframe bushings not a good choice?

[dadsbmw]

Went against my better judgement recently and brought my car into a "reputable" shop to get a misfire diagnosed. Despite not being asked to, the tech felt it necessary to do an underbody inspection and specifically called out: "stock rear sub-frame bushings (replaced but still OEM and not recommended)." I definitely brushed this off as nonsense, but am now curious if there's any actual truth to this?

Is there anything wrong with running stock (Lemforder) rear subframe bushings? Should I be using something stiffer? Poly? Delrin? Aluminum?

I mainly ask because as I do research for my Z4, which basically has an E46 rear subframe, the consensus is to go with much stiffer bushings at the connection of subframe to body, to reduce stress at that joint and put all the stress on the mounts from subframe to trailing arms/diff.

[nando]

There's nothing wrong with stock subframe bushings, unless it's a dedicated track car and you want to stiffen everything up. Maybe he's thinking of the E46 or something? Unless there's damage I wouldn't worry about it. E30s that aren't rust-buckets don't typically have subframe mount issues.

There are softer poly bushings that are fine for the street, but I definitely would not run solid delrin or aluminum, unless you want to rattle your teeth out. And if the stock ones are new there's not much reason to replace them anyway.

[zwill23]

As someone who dropped their subframe four times trying to achieve the right streetable setup for me, poly subframe bushings with rubber trailing arm bushings is my recipe. When I went poly on the trailing arm bushings I could not get them quiet down for more than 5k miles or so, and the creeks drove me nuts.

That tech sounds like a goon, rubber subframe and trailing arm bushings work great! I agree with Nando, E30's didn't suffer the same subframe problems as E46's and if they were replaced with new rubber don't bother messing with them.

[Victell]

I went with all new rubber for my rear subframe and trailing arm bushings. Very happy with the results. New rubber feels great and no noise.

[dadsbmw]

Thank you. Glad to feel vindicated of my distaste for this tech/shop. They made several claims, assumptions, and judgements (I'm fine with you telling me there's a pinhole leak on a weld, but I don't think you need to tell me there's a pinhole leak AND my welds are poor. I'm well aware that I'm not a professional welder!) that were wrong and IMO unnecessary.

[nando]

I went with all new rubber for my rear subframe and trailing arm bushings. Very happy with the results. New rubber feels great and no noise.

I don’t doubt your experience, I must have been lucky. I’ve had the same Ireland Engineering poly bushings since 2003, and they have never squeaked. I did use some sort of silicone grease on them (I was 24, don’t ask me to remember that far back). So it was either dumb luck, or magical grease. Not sure.

[hoveringuy]

I have a mostly-track car and I still run rubber trailing arm bushings and poly subframe.
The subframe is poly mostly because I'm hoping it will take stress off the differential bushing by allowing it to move less.

[moatilliatta]

Take a look at groupe N mounts. Better then soft poly.

[dadsbmw]

Take a look at groupe N mounts. Better then soft poly.

I mean I've got brand new Lemforder mounts in them already, I'm not looking to replace them for no reason.

[digger]

Take a look at groupe N mounts. Better then soft poly.

Got a P/n ?

im about to do mine. Was going to use oem but fill holes rubber compound

[moatilliatta]

Motorsport Gr.N rubber bushing cross member - 33311417247 X2

If the local dealer is being cocky - https://www.turnermotorsport.com/p-3...rack-e30-pair/

Last set I mached off 12mm to raise the subframe up and added a 12MM cup shim below it.