RSFB inserts to full M3 bushing swap?

[mhullihan]

Over the 1.5yrs I’ve had my 128i I’ve always had a softer than I’d like rear axle feeling that’s bothered me. I’ve had other priorities on the car until now but it’s time to address this. The roll stiffness balance seems biased forward and the purely lateral RR stiffness feels low leading to a disconnected feeling front to rear, especially during weight transfer.

The car came with a lot chassis upgrades: koni yellows with H&R springs, white line RSFB inserts, and up front there’s M3 arms, sway bar (roll stiffness balance cause), and dinan camber plates.

My options seem like RR sway bar, M3 RSFB, or going full coilovers with much higher spring rates. I put in an LSD btw.

Does anyone have experience going from inserts to proper M3 bushings? Is it noticeable? I’m leaning toward this and the RR bar purely from a cost perspective.

Thanks in advance!

[Olgeezer1]

Well, I used Whiteline 2 pc. poly bushings for easier installation. My guess is they're a little more firm than the M3 bushings. Previously had the Whiteline inserts which were really a half way measure. I use a local high speed sweeper with a bump half way through to gauge effectiveness. Stock bushings a little scary on hitting the bump, inserts an improvement and 2 pc. poly pretty much solved the problem. For the sway bars - E93 M3 front and 15mm. rear (with LSD). Stock Sport Pkg.springs w/ Bilstein B6. Dinan camber plates. So yes, I think upgrading those inserts will make a noticeable difference. Hope this helps.

[ShocknAwe]

Had inserts. Went with full aluminum bushings when I redid my rear end. Highly recommend skipping the intermediate options.

I don't have any polyurethane anywhere in my suspension and I'd recommend you avoid it too since it's possible these days.

[mhullihan]

Thanks for the feedback guys. I hadn’t thought of either of these options. Time to do some reading.

The 2-piece idea sounds nice without having a press in my garage. Does it add any height to the mating surface like the inserts? Are the solid bushings also 2-piece? How’s the NVH difference with poly or solid mount?

[ShocknAwe]

Originally Posted by mhullihan

Thanks for the feedback guys. I hadn’t thought of either of these options. Time to do some reading.

The 2-piece idea sounds nice without having a press in my garage. Does it add any height to the mating surface like the inserts? Are the solid bushings also 2-piece? How’s the NVH difference with poly or solid mount?

Solid aluminium is solid. No additional NVH unless you do differential bushings too.

[Blau]

I'm very happy with my white line poly 2 piece bushings. I did the diff carrier as well. Decently straightforward job. Get the subframe tool from eBay, it's totally worth it. I didn't have such luck with the diff bushing tool and ended up making my own.

I have noticed zero NVH since doing the job. It's a 128i so I didn't think alu was necessary.

[AshwinLB]

Condor Speed Shop RSFBs are two piece solid UHMW and was really easy to install at home without dropping the subframe completely. I got the ebay tool and it was no fuss getting the old rsfb out (even with ~165k km). I did remove the brake lines that connect the subframe to the chassis, and teetered the subframe by tightening the opposite bolt to the one I was working on almost all the way, while leaving the 2 bolts beside it with 5 threads in. (ie, working on rear left, tightened front right almost all the way and front left/rear right with 5 threads in).