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.

[digger]

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.

Are there GrN TA bushes as well if so what are the P/N? i thought i had seen them listed somewhere but dont recall where i had seen them

[moatilliatta]

One thing I found the group N stuff has been setting for a while it may deteriorate just a quick as IE goop. I don't have the group N part number.

These bushings cant be that hard to have remade in solid rubber by now...

[Holland]

Old thread but I will chime in on the debate. I ran "street" poly bushings on my 85 the first time I did them. Rubber TA bushings. I hated them, there was some noise but I could actually feel them flex under load and deflect which gave the rear of the car a lack of stability. I replaced them with solid aluminum and what a difference. This is a street car, but built with occasional trackability in mind. There is no discernible difference in comfort that I can fee, what you will notice with aluminum however, is that the noise and vibrations will resonate throughout the car a lot more including any resonance from the diff. So not good for the street if you are looking for comfort. If you are looking for old car visceral then they will aid in that. Feel is probably the best out of any other option if that is your priority, I love these things a lot.

[digger]

Under load the rubber TA bushes can move alot like 1-2mm radially under very hard lateral and longitudinal load (i build a ANSYS FEA model of one) which sometimes makes you wonder why stressing over a fraction of a mm in an alignment.....

The poly bushes on the market are just garbage though the thick and thin protruding pat (i call the hat) are all over the place dimensionally, and the bushes push into the arm too easily yet pins need to be hammered in so when you tighten the bolt the bush sometimes spins in the arm rather than the bush rotating over the fixed/clamped pin

Its no wonder people have squeaks, to get them to work properly and reliably i would have to make new shorter pins to fit a large OD washer at either end so the poly bush hat bears on the washer to act as the axial bearing rather than the slotted hole in the subframe caused by the adjuster and this way i can custom machine down the protrusion/hat thickness to a nice snug fit as each manufacturer has different dimensions for the thick and thin end. i will fit teflon tape to the pins might adjust the OD of the pins a few thou and maybe add some kind of goop to prevent the bush spinning in the arm