[jzx_andy]

OP, I'm sorry that this has resulted in a fail in your case.

What other mods do you have? While NVH is subjective, I find the question of how "noticeable" NVH from mods is highly dependent what you've done (or what you haven't done) to the rest of the car.

If your car is completely stock, oem exhaust, mounts, factory clutch etc, I would think some people would find certain mods almost intolerable in terms of NVH, due to how quiet a factory specification e9x is overall. Just imagine a bone stock e9x with upgraded engine mounts, it'd probably feel like something's out of place since the vehicle will really only resonate a lot of NVH while idling, and completely goes away the moment you accelerate/cruise. On the other hand, that sort of NVH would feel more "natural" on a car that's gone the whole 9 yards with a louder exhaust, rear end, tyres, etc. In the latter case, the vehicle would be louder than a stock e9x under all conditions - idle, load, cruising at speed, etc, but the noise wouldn't be coming from one area.

I would presume you perceive subtle changes in NVH quite well and/or have a very tame example of an E9x, given that you refer to all season street tyres as being "a little noisy". There is nothing wrong with this perception, though it is a useful reference point for when NVH becomes noticeable in your specific case.

That said, a lot of people who go for solid subframe bushings would have already done various other modifications that each increase NVH in their own way, such as an aftermarket exhaust, single mass flywheel, engine mounts, trans mounts rear shock mounts, coilovers, larger wheels, dual use road+track tyres, etc. These other modifications coupled together help to balance and, in effect, drown out NVH that's coming from one specific source.

I opted for PLM solid subframe bushings on a car that sees street use 99% of the time. I fitted them shortly after having done a bunch of other upgrades, inclusive of poly engine mounts (which I found add a noticeable amount of NVH and would recommend against from a cost vs benefit vs comfort analysis). The only item I've left alone at this point is the factory catback. All that said, I found the NVH increase from solid subframe bushings to be minimal and I'm ok with the upgrade.

Do let us know how you fare once you've replaced them for something else. All the best.