Another rear subframe bushing question

[tryffis]

Hey, so i guess this is better place to ask about the m3 bushings.

So i am fitting whole m3 suspension to my 335, and just wondering if there is any point to upgrade bushings to 90sha urethane ones since the subframe is already out?

I know most of you will recommend the solid ones but the car is truly daily driver, and i think and the cost of them will be probably 4x urethane ones for me installed.

Oem bushings on the subframe are less than 20k miles driven.

So anyone with swapped poly bushings, any noticeable differences?

[pbonsalb]

I would go stiffer on the subframe bushings. I run 75D on my E90M3. It’s close to Delrin, which is close to aluminum. Those are also fine. There seems to be no NVH downside. Stiffer Diff bushings will result in whine, which can be obnoxious if it’s bad. I used 95A for the diff and there is still some whine.

[Redd]

Powerflex Purple rear subframe bushes are $387. Turner solid subframe bushes are $330. Just go solid.

[tryffis]

Originally Posted by pbonsalb

I would go stiffer on the subframe bushings. I run 75D on my E90M3. It’s close to Delrin, which is close to aluminum. Those are also fine. There seems to be no NVH downside. Stiffer Diff bushings will result in whine, which can be obnoxious if it’s bad. I used 95A for the diff and there is still some whine.

Yeah im pretty aware that incase i keep my stock diff ones, nvh shouldnt increase much/at all. Yeah i hate that diff noise too, i had pretty noisy diff on my 335 until it totally blew, well that noise was obviously about bearings or blacklash etc.

Originally Posted by Redd

Powerflex Purple rear subframe bushes are $387. Turner solid subframe bushes are $330. Just go solid.

Yeah well that would be the thing with powerflex. I'm looking at strongflex yellow ones, wich would cost me 120 eur shipped to my door, and no tax. If i get turner ones, its like 300 eur + shipping ~50€ + taxes and customs about 30%. And possibly install takes 1-2 more hours.

But the real question is that 90a bush like 0-5% better than oem or like 25% better, incase the second, its definetly worth that.

[wyatth]

I think at 20K, the original bushings will be like new. If you are into your car enough to go through with an M3 subframe swap anyway, I think you'd also appreciate doing stiffer mounts at the same time. I have never heard a downside or regret related to solid. If not solid, I would just use the M3 bushings already pressed in.

[Redd]

Then just get the stiffest PU Strongflex has to offer.

[pbonsalb]

90A is soft but still stiffer than stock. Powerflex Purple is 80A. I use 75D. I think on my E36M3 I have Powerflex black and they are 95A but I put them in years ago and cannot remember.

https://www.akgmotorsport.com/materials-chart/

[Redd]

If you're already going thru the hassle and cost of putting in a whole M3 subframe, why worry about the small savings of poly vs solid? Just do it right one time and go solid.

[pbonsalb]

Solid is more trouble to install than poly and poly works well.

[tryffis]

Thanks guys for replies, i truly agree that solid ones would probably be best upgrade, but already streching my coins to get the car back on street. So solid ones are out of question for me now. Some people have been using both m3 and poly bushes on regular e9x cars and noticed poly ones to be little better than m3 regarding sideways movement. Truth is that probably differences between the two are so nominal since that m3 bush is not even regular bush, because loads of solid metal inside compared to regular e9x crap.

Well i think maybe the best option would be to stick with oem, unless i manage to find solid ones inside eu for reasonable price. Its still million times upgrade in place of stock hollow ones i had.

How abouts the wheelhop, i managed to blow my current diff due to that, so do you guys have same issues with m3 aswell?

[Redd]

Stock M3 subframe bushes still have wheel hop and still allow the rear subframe to deflect a huge amount under load. It's why so many of us go solid in the first place.

[pbonsalb]

I noticed the difference between my M3 bushings (car was 7-8 years old and had maybe 70-75k miles at the time) and new poly 75D subframe bushings. It was immediately apparent to me. My original bushings looked to be in good shape, but maybe new M3 bushings would have also made a big difference.

With the M3 bushings, I notice on high speed transitions the rear end moving back and forth a little. It happens at lower speed cornering also but I notice it most at speed. With the 75D poly, the rear end simply takes a set and does not wiggle.

A friend with a 135i tried inserts into his stock bushings to make them more M3 like. The rear still wiggled, much like an M3. He had me test drive it. Then he changed to hard poly. He had me test drive it again. No wiggle.

I’d go 75D, delrin or aluminum.

Reduce movement in subframe and you will reduce wheel hop, but there is more too it. You would probably need to redo the rest of the suspension and stiffen the rear springs. Wheel hop is hard to banish. I’d work on your application of power, which is much harder to finesse with a turbo. Clutch drops won’t help. You have to feed the power in. My E90M3 tends to just light up the rears and not hop. I would try to find some 335i drivers to get their input since the suspensions differ. Maybe N54tech dot com. It used to be the most active forum and had some drag racers who know more about wheel hop.

[amrazM]

for the 10000000th time, solid in the subframe to body mounting points has zero effect on NVH.

[pbonsalb]

The OP has explained he does not want to do solid because they cost twice as much in his area and take longer to install (which matters if you are paying shop labor). I could have bought and installed either since the cost difference was small 4-5 years ago and I was DIYing, but did not think aluminum was worth the money and trouble over 75D poly.

[wyatth]

Curious, why is solid harder to install? First I've read of that. I only have experience with poly (95A in my E46M - it was a nice, but subtle change).

[pbonsalb]

Poly are in 2 pieces. You can install by hand. Solid must be pressed in.

[M43S7RO]

Originally Posted by wyatth

Curious, why is solid harder to install? First I've read of that. I only have experience with poly (95A in my E46M - it was a nice, but subtle change).

You need a press for solid which I diy'ed. I also did poly for all the other bushings on the subframe and I was easily able to push those in by hand. Judging on that, I'd think the subframe poly bushings press in pretty easily by hand, especially since they are split in half.

[BayE30]

Originally Posted by pbonsalb

Poly are in 2 pieces. You can install by hand. Solid must be pressed in.

Unless you have the 2pc solid subframe bushings i bought from Slonik. no press required.

[wyatth]

Good to know!

AKG looks 2pc as well, but not positive:
https://www.akgmotorsport.com/produc...m-e90-e92-e82/