M140i Upgrades // Part 8: Powerflex Bush Inserts - Rear Subframe & Diff Void Fillers

[@akent46]

A concise subframe understanding.... The subframe is held in place by bushings on the end of the axle, and the diff mount on the rear end of the diff. The subframe is NOT designed to hold the weight of the car! The weight of the car is transfered to the trailing arms/wheels by the shock/spring assembly. The subframe is only there to keep the trailing arms in place, resisting the sideways and accelerating/braking forces. (Of course the subframe/diff bushes do get some vertical forces to resist the resulting forces from the torque that is transferred to the wheels, these are a lot smaller than the force that the actual weight of the car would give.)

[@vollcare4076]

Great to have you (and the footage) back here 👍

[@CIRCUITDRIVERCARS]

Cheers mate 🙌

[@AH-007-75]

It really is when all things combined together on these cars work in synergy with each other the little (big) things all add up.

[@CIRCUITDRIVERCARS]

When you drive them back to back with standard or more standard cars you realise what a difference all the parts have made as a whole. Even if some of the improvements like these are quite subtle. 😊

[@coenwag]

Hi all, I have watched tons on videos on diff and subframe bushings. I took me quite sometime so decide which ones to fit. I went for powerflex full back ones and a powerflex purple diff bushing. There is zero diff whine!! The subframes now feels so much more connected. I high recommend. The noise is totally fine to live with, it’s a bit more like that sound that you have when you drive on really rough tarmac. That’s it.

[@DjNikGnashers]

Thanks for another informative video matey.

[@CIRCUITDRIVERCARS]

Cheers Nik, shame it took so long. Glad to have restored the footage. 👍

[@dobbyboy3116]

Great review! looking at both inserts and the brace.

[@CIRCUITDRIVERCARS]

Glad it was helpful!

[@johnshaw8013]

Back in the day... 20yrs ago, I used to make solid Ali rear subframe bushes for the Nissan 200SX which I was heavily involved with through SXOC... They transformed the handling without being bad for NVH... miles better than poly bushes!

[@daysofgrace2934]

That what i notice compared to my 2009 Boxster vs 2005 120d; the rear of the 120d i can’t tell what going on, it doesn’t communicate. The Boxster tells me exactly what’s happening therefore i feel confident in pushing on. I’m getting the inserts done with SuperPro bottom mounts and PowerFlex rear top-mount bush. I’ve already got Koni FSDs, BMWP bumpstops and Eibach Pros on and changed the the rear and front top-mounts via the BMW repair kit. Next up will be changing to 1M/M3 LCAs and tension struts...

[@martinlee7706]

antiroll bar is a MUST , u will feel not shaking while in sharp turns

[@CIRCUITDRIVERCARS]

Which bar/bars did you go for Martin?

[@martinlee7706]

@@CIRCUITDRIVERCARS H&R purple ones front and rear on my M140i Arran Senior (senior perform) fitted them ....

[@allanmorris6324]

Hi mate. What do you reckon would be labour costs for front and rear subframe inserts? I'm being quoted 250-300 plus vat. Seems a lot. Thanks

[@AGM240i]

Does it help with the little bit off clunk from diff ?

[@Poontang123]

Hello Who fitted the diff please need a reputable installer cheers

[@paulhein64]

New to this and thinking of an LSD from my BMW dealer who have a special offer on and so was interested in the void fillers. Do you have a bit more info on the product please? Also what is NVH?

[@MrAshLloyd]

Noise harshness and vibration

[@paullasky6865]

Had my m240 1.5 years. I'm one of the few people that enjoys the powerful engine combined with the comfortable ride. I don't want to feel every bump through the road. I got rid of my i20n because of that. I have taken it on track and learnt how to handle it stock. Now I have the best of both worlds a nice comfortable ride when I want it and when I want to drive spirited I have the confidence to. I don't really understand the obsession with modifying these m lites handling. Just get an m2 or m4 theyre not that much more expensive and saves a lot of faffing and mod costs. As the says the point of these cars was to have most of the power but with a livable every day ride. Nothing worse than going over a pothole and filling it all the way through your steering wheel into your teeth

[@CIRCUITDRIVERCARS]

We’re in perfect agreement Paul, I had an M4 alongside the M140i and a key consideration with the M140i was to retain its excellent comfort and usability. Throughout all the modifications I thought carefully about not compromising the car with choices of parts and what I ended up with was still much more comfortable and usable than the M4, but with greater competence and genuine reward as a drivers car. It was a superb package. 😊

[@paullasky6865]

@CIRCUITDRIVERCARS since I wrote that comment I have booked a stage 2+ power upgrade 🤡🙈🤦. Still not touching the suspension though. Maybe an lsd if I find the power a bit much.