TMS solid *delrin* vs aluminum subframe bushings

[BTB]

Howdy y'all,

I was always planning on using the Turner solid aluminum subframe bushings for my rear end rebuild, but I see they now have an aluminum/delrin bushing that's a little more expensive. Anyone know what the dealio is with these? According to a rep at TMS, the delrin is preferred on some hardcore race cars as the solid alu can be too stiff. I don't totally understand this especially for a totally caged car, as newer M cars have solid metallic mounts here. Based on the description I thought the solid alu mounts maybe weren't legal for certain racing regulations but I was told that's not really the case.

TMS solid alu description:

"While our Delrin-Aluminum subframe mounts conform to various racing series these all-aluminum mounts are the ultimate in reducing flex and deflection. The rubber stock mounts, and the Delrin mounts to a small degree, flex and deflect as various forces are applied throughout the subframe - on and off throttle loading, cornering on flat surfaces, bumpy surfaces, weight transfer, sticky race tires, etc. Too much flex from worn rubber mounts will transfer to flex where the subframe meets the chassis/floor. This is the primary cause for the infamous rear subframe failure. These fully solid aluminum mounts have absolutely zero flex to them so they will not contribute to rear subframe issues. The Turner E46 Reinforcement Kit is still recommended."

It seems like the delrin is more popular for e9x, e82, I feel I've heard more about the aluminum mounts for E46. What gives? My car specifically is a street car/road trip car also used for track days and maybe some light rallyx/autox stuff.

[BTB]

Presumably the delrin helps to slightly mitigate mechanical shock? Doesn't sound like a bad idea to me as long as it retains the good qualities of a solid bushing ie no or very little cyclical deflection on a significant scale. Still, to me solid aluminum is more wet-dream inducing ..

[Tbonem3]

I feel like the subframe is a fine place for poly, delrin, nylon or solid. I'd care more about the "footprint," and if the bush is shortened to accommodate for RACP plate thickness.

[AussieE46M3]

I can't imagine the difference between aluminium and a hard plastic provides any measurable difference in impulse dampening to the chassis. As you mentioned, the F8X gen M cars have the steel subframe fastened right to the mounts with about a 1.25" contact patch.

I would encourage going for aluminium especially if it's cheaper.

If you're open to suggestions here's another solid aluminium subframe bush option that works out about the same price after shipping from Aus. Comes with a bit of an eye candy factor

https://cmpautoengineering.com/collections/all/products/e46-z4-solid-subframe-raising-bushes

[S14]

I have bimmerworld solid bushings in the subframe and OEM in the diff and the car is not harsh at all on the street. I've driven in other BMW chassis' with poly or solid motor/trans/diff/subframe mounts and the NVH was noticeable. It is not noticeable in my car unless I have the trunk carpet removed and the rear seats removed, then I hear a bit of diff whine.