Objective bushing comparisons

[Maybe Magpie]

Has anyone done one before? A lot of companies (AKG, Condor, Garagistic, et al.) insist their bushings don't increase NVH but I hear the exact opposite almost universally from other E30 owners. Durometer is durometer but I'm curious if a high durometer rubber and high durometer poly have the same characteristics in terms of NVH, and which bushings to avoid using poly for if I want to keep NVH to a minimum while improving over stock. "Oh they don't squeak and rattle" "Yes they do" he-said-she-said is hard to discern. I would have gotten the Group N bushings but they went out of production sometime after 2019 and are NLA, they're essentially stock but solid rubber.

The thing is one person's "fine" NVH is another's "miserable", so I was hoping to find some sort of meaningful comparison, if not of bushings in-situ, of materials and durometer ratings and the like. I mostly street my car but I don't want to rattle my teeth out on my area's shitty roads. I know the E30 is a 40 year old car, I don't expect it to be silent or perfectly smooth but it's already vibrating enough as it is with an exhaust on it and I don't want to make it miserable to daily.

[digger]

This is a loaded question as the specifics and details matter including the operating environment (type of road surfaces and imperfections encountered) and the application e.g. which bush in particular and intended usage and then there is personal taste/perception and point of reference.

The softer poly might be acceptable to some tastes on certain bush locations depending on usage but will never be as comfortable as the OE rubber period. E.g. Antiroll bar bushes are pretty safe though companies like whiteline and H&R use a better poly than places like IE whos bushes are rubbish (unnecessarily hard)

Which group N bushes are NLA? sub frame were last time i looked

[Maybe Magpie]

This is a loaded question as the specifics and details matter including the operating environment (type of road surfaces and imperfections encountered) and the application e.g. which bush in particular and intended usage and then there is personal taste/perception and point of reference.

The softer poly might be acceptable to some tastes on certain bush locations depending on usage but will never be as comfortable as the OE rubber period. E.g. Antiroll bar bushes are pretty safe though companies like whiteline and H&R use a better poly than places like IE whos bushes are rubbish (unnecessarily hard)

Which group N bushes are NLA? sub frame were last time i looked

Those are the ones I meant, yeah. I haven't ever found Gr.N bushings for the RTABs et. al or anything else, despite some hunting. Wide open to P/Ns if you got 'em. FWIW I'm in the PNW and here we have a ton of elevation and while a decent amount of our roads are okay in smoothness it's really not uncommon to find enormous, shockingly deep potholes or cracked up surface. Some of the more important stretches of interstate are in a not-great way, too.

The thing about it being loaded is that's why I want to figure out some kind of baseline and work from there. For my purposes of street car with occasional autoX and spirited backroad that I daily I want something quite soft but a little stouter than stock, the problem is I don't have access to an E30 with poly to compare NVH against mine, etc. I know durometer is for hardness, is there a good measurement for vibration transmission? Something to do with frequency, maybe?

[digger]

33311417247 group N rear subframe bushes can still be found. they arent cheap and tbh i have a set (not installed) and they are at most a subtle upgrade as the rubber is supposedly slightly stiffer but the geometry looks the same not completely solid. Better to by a stock set and fill the voids with 70 shore A casting rubber. It is possible the legit Group N are superseded and now just the stock version is sold under group N guise (based on what i received it wouldn't surprise me)

https://www.m3-klassik.de/images/TK_E30_N.pdf

[Maybe Magpie]

33311417247 group N rear subframe bushes can still be found. they arent cheap and tbh i have a set (not installed) and they are at most a subtle upgrade as the rubber is supposedly slightly stiffer but the geometry looks the same not completely solid. Better to by a stock set and fill the voids with 70 shore A casting rubber. It is possible the legit Group N are superseded and now just the stock version is sold under group N guise (based on what i received it wouldn't surprise me)

https://www.m3-klassik.de/images/TK_E30_N.pdf

When I looked into it it was NLA on turner and ECS and FCP and all over et. al as well. The stock Febi and Meyle ones are both offshored now, though the genuine 33311130537 (standard type I think vs the Gr. N) appear to still be made in Germany if ECS's CS is to be believed, but $150 for stock-stock rather than N is a hard pill to swallow. If there were ones made in like India or Turkey or Romania or something I'd just fill those and send it but there don't seem to be anymore.

[Panici]

I went from a fresh set of OEM rubber bushings to Revshift 80A Polyurethane Differential, Subframe, Trailing Arm Bushings.
Those were the softest Poly bushings that I could find.

Made the change to control wheel hop while keeping soft spring rates on a 24v swap turbo car.

They definitely met the goal of reducing wheel hop, however I did notice the NVH increase.


If I had left the 24v swap naturally aspirated making less power I would have stuck with the rubber bushings.
But at 300+ WHP I was going to break something with how the tires were shaking in first gear.

[Maybe Magpie]

I went from a fresh set of OEM rubber bushings to Revshift 80A Polyurethane Differential, Subframe, Trailing Arm Bushings.
Those were the softest Poly bushings that I could find.

Made the change to control wheel hop while keeping soft spring rates on a 24v swap turbo car.

They definitely met the goal of reducing wheel hop, however I did notice the NVH increase.


If I had left the 24v swap naturally aspirated making less power I would have stuck with the rubber bushings.
But at 300+ WHP I was going to break something with how the tires were shaking in first gear.

That's good info, thank you. I'm not going to be making that kind of power with an NA M20 bar a five-figure build that isn't on my dance card or in my wallet I think, so I suspect gritting my teeth and shelling out for the Gr. N ones from Schmeidmann might be my best bet even if the cost is ludicrous for what they are. Unfortunately none of the companies that sell poly bushings seem to be willing to sell the metal sleeves the bolts go through by themselves and machine shops want like $800 for all the ones I'd need, otherwise I'd just cast the bastards in 60-70A rubber.

[digger]

That's good info, thank you. I'm not going to be making that kind of power with an NA M20 bar a five-figure build that isn't on my dance card or in my wallet I think, so I suspect gritting my teeth and shelling out for the Gr. N ones from Schmeidmann might be my best bet even if the cost is ludicrous for what they are. Unfortunately none of the companies that sell poly bushings seem to be willing to sell the metal sleeves the bolts go through by themselves and machine shops want like $800 for all the ones I'd need, otherwise I'd just cast the bastards in 60-70A rubber.

you could get a set of the pins/sleeves made for sub $200 with one of the CNC places like Xometry Et al i would think based on what i have gotten made.

[Panici]

You're talking about Group N subframe bushings?

What about just stock rubber bushings and fill the voids up. I seem to recall some threads on here with that discussion.


Regarding front CAB (lollypop) I went with solid rubber E30 M3 offset bushings.