Are Current OE Rear Subframe Bushings Improved?

[old///MFanatic]

Glad to hear you're happy with your decision. What did you end up going with?

I talked to people on other forums, BMWCCA community members and two race teams shops in SoCal. All that used them had nothing but positive reviews, so went with Condor Speed Shop sub frame bushings.
If my product impression changes I will certainly post about it on forums. I have no horse in this race.

[Ramps]

I installed my CMP solid subframe bushings about a month ago along with all new OE / OEM ball joints, bushings, diff bushings etc. Every wear item in rear end.

I can also speak to the solid, responsive feel without any noticeable increase in NVH, and I am picky when it comes to NVH. The car feels better than new! Anyone on the fence, don’t bother with stock subframe bushings, there is literally no downside to the solid ones.

[AussieE46M3]

What a strange coincidence you posting yesterday. As I just had my first drive with the new bushings installed.

As many said there is no significant NVH. Suspension feels real good back there now. So far I am pleased with the change and thank all those for pushing me to upgrade over the stock version. It feels real tight back there and as if the spring/shocks are able to do their job more direct.

Glad to hear you're happy with your decision. What did you end up going with?

I feel it really transforms the back end making it tighter and far more responsive.

You're spot on about the suspension doing its job better, as the springs are mounted on the upper arm, the subframe bushes also flex under spring forces which are quite high due to the motion ratio on these cars.

[old///MFanatic]

What a strange coincidence you posting yesterday. As I just had my first drive with the new bushings installed.

As many said there is no significant NVH. Suspension feels real good back there now. So far I am pleased with the change and thank all those for pushing me to upgrade over the stock version. It feels real tight back there and as if the spring/shocks are able to do their job more direct.

[AussieE46M3]

Yup, I was expecting it to be somewhat off. Car is now (moderately) lowered and rear camber maxed out at -1.3 deg.

I do see some camber arms in my future though.

Hey guys,

Sorry for such a late comment. I don't spend much time on the forums these days so I'm a bit slow to messages and tags. Sorry if you've tried to contact me here.

Saw I was tagged here so figured I'd add some comments.

One thing I wanted to mention to this part of the discussion, I've very recently released some adjustable camber arms of my own design for those looking to purchase the CMP subframe raising bushes.

Hope you don't mind me plugging it but, felt it was relevant. https://cmpautoengineering.com/colle...le-camber-arms

Best thing about the CMP RTABs is that they use a lemforder (I think) bearing. So if it wears out you can just press a new one in. No need to get everything again unless it's for another car.

Correct. The lemforder ball joint part number is 3067901 however, also listed in the instructions included with the bush.

Also, thank you for all the amazing support for my products. I appreciate that very much! I'm glad to see you guys are enjoying them as much as me.

My take on the does solid make cracking issues worse is that in theory, there's less dampening to driveline impulses loads (clutch kick/dumps, sudden off and on throttle, launches etc) not static loads like cruising as once the rubber flexes sufficiently to transfer the force (like a spring) the magnitude is the same. I feel not many guys are launching their cars too often and even then, with sufficient reinforcement this is a mute point.

On the other hand, as the rubber deteriorates it will allow excessive flex eventually causing the steel hoop inside the bushing (to make it stiff enough for a press fit) to lunge into the chassis. This happens on even brand new bushings however, gets much worse over time. The major issue here being that there's two lobes on the stock bushings that sit proud that the steel core is in which exerts a lot of force in a very localised space. This is the causing of cracking on the front right subframe mount 99% of the time.

I have seen cars that have been reinforced with the old style turner plates that were very thin and stock bushing and have managed to deform even the plated surface. Some even cracking beneath the plates however, I cannot say this is entirely because of the bushes as I've seen plenty of dodgy repairs although, the plate deformation can't have been helping. I would personally suggest as other have, a very hard subframe bushing and stock diff bushings.

One thing to be mindful of is how the bushings retain themselves on the front studs. I've seen some cheaper options have a small hole for a snug fit on the stud on one side and a larger hole (like the rears) on the opposing. This essentially means that if the clamping force on the stud isn't sufficient the subframe can pivot around that front stud under cornering forces as well as the one snug fit stud is bearing the entire cornering force of the rear wheels. It can be tight to fit at times however, this is why I went with a snug fit on both front studs to prevent this and do what I can to insure the force is spread evenly over both.

I've looked into UHMW plastic and it's got pro's and cons. It's a self lubricating material generally used for chain guides etc or other low pressure rubber surfaces from memory. Technically there will be more flex however, IMO so minimal that there's nothing to gain however, the two piece construction eliminates the possibility of doing a raising design so there is something to lose.

I won't shoot it down and acknowledge it can be used in places such as this and possible diff bushings provided it doesn't deform like most poly's do under the pressure (as it's not as strong) although, have considered it for insert in a spherical bearing for a FCAB however, I believe there are stronger and more durable grades of plastic. Yet to get very far on that.

I personally went poly after my car was reinforce the first time and now suggest the combination of solid & stock as if done correctly gets the best of both worlds although, it is a balancing act of compromise so it's entirely down to your own preference.

A quick comment on NVH. You've got noise, vibration and harshness.

Noise is pretty basic. It can be caused by the engine, the trans, the diff which shouldn't be heard on stock bushes/mounts. Engine being injector, valvetrain, accessories and hopefully not knocking. Then you've got other factors such as induction & exhaust which are mostly desired noises and lastly environmental like tyres in motion, wind around the car, rain on the body and interior squeaks, rattles etc. Keep stock engine/trans and diff and essentially the ones you don't like that you can control won't change. I found poly subframe/diff to be much worse and can say the same for engine/trans.

Vibration is essentially a product of things that produce vibration. The biggest cause and almost the only is the engine with the gearbox and diff technically producing very very small amounts. That should be it unless you've got something rotating out of balance or alignment.

Lastly, harshness. For something to feel harsh it's generally the product of an impact (like a pot hole) this is generally related to whatever prevents the wheel from moving forward or backwards in the guards (RTAB & FCAB) or up and down (shocks & springs). I can report that the RTA bushes will make impacts harsher although, just like the subframe bushes, only when they happen.
If you are just driving down a normal section of road and not over pot holes, reflectors, speed bumps etc, nothing is pulling on the wheel and therefore you wont notice a difference at all. A bearing type RTA bush will not suddenly add vibration to the car, it just reduces the elastic dampening to impulses. On the plus side you gain quicker inertial response (like how a car will have less body roll with stiffer springs).

Upgrading subframe and control arm bushes to bearings (in the context of cornering forces) should make negligible change to NVH as cornering forces are not impacting and build up slowly by comparison as you wind the wheel around and the body rolls loading up the springs and thus pressure on the contact patch. This is where M3's had 2 of the 4 bushes mounted on ball joints joints compared to just the 1 of 4 Non-M's had. CSL's went a step further by having only a single piece of rubber in the upper in arm as they use different camber arms with the same ball joint. The advantage of doing this is more consistent camber geometry due to greater link stiffness.

In short, keep engine/trans/diff/FCAB & RTAB stock and it should feel as soft as a stock car. Everything else can be upgraded with negligible compromise. Note: Not talking about prop donuts, CSB etc. Keep those stock.

If you want to do better and have more consistent toe geometry (=stability/predictability) consider monoball RTAB's followed by bearing type FCAB's.

Hope that helps with your decision making and sorry for the long comment. Didn't mean to blab on but it keeps happening.

[Tbonem3]

Agreed, and it was only a guess on m3f that solid would be ok since it comes that way on new bmw Ms.

As it pertains to you, it was also guessed that rubber bushings cause cracks as they give and subframe can rock and pull on racp.

I hedged my bets with poly, big foot print, more solid than rubber, but gives vs solid. Plus no rotation, which is why only poly on my car is camber plate, subframe, diff & rsm. Fcab rtab and control arm inners must be rubber or bearing.

I for one appreciate you mentioning the condor ones, I think they're worth a shout, though r4dr's comment causes pause.

Having said all this, it could just be a abundantly cautionary sales disclaimer. It does not prove that manufacturers of solid e46 m3 sub bushings truly believe installing them will cause worse fatigue.

[old///MFanatic]

Dude everyone here is telling you there’s no noticeable difference in solid mounts vs OE rubber mounts. The condor ones are so similar to solid that it makes sense to just get the solid ones. It seriously doesn’t matter. You aren’t sacrificing anything here...

I get that majority in thread is contributing there’s not much difference in NVH at this point. Accepted.
Manufacturer of aluminum mounts states CON of solid is harder on impacts at the studs. *Best to use with bottom and topside reinforcements. So there’s that straight from the horse’s mouth.
I’ve currently asked between Solid aluminum and Condor Speed now because I’m between the two. Similar lack of material flex but some design differences. Now I’m simply asking for anyone in the know what are Pro/Cons between those two. Not hearing any. Since no one yet has provided info that aluminum solid are superior then Condor Speed appears in the pros vs cons best choice at this point. If “top hat” or lack of is better or worse that would be a factor. Vince mentioned this.

Your point they’re similar is not lost on me, I already considered that. Just looking for knowledge from a few here who actually know this stuff compared to other forums where true details aren’t known because they must pay people to work on their cars and know very little. This forum actually has legit knowledge from a few. That’s why I am here.

[r4dr]

Hit a chef knife on a professional culinary cutting board (similar material). Then hit that chef knife on an aluminum board.
Seems very possible it absorbs some vibrations that aluminum would not. No?

It's been a while since I remember the debates on R3vlimited, but one major downside of UHMW is that it's not as solid as metal but also doesn't rebound like poly.

[SteelGreyM]

Dude everyone here is telling you there’s no noticeable difference in solid mounts vs OE rubber mounts. The condor ones are so similar to solid that it makes sense to just get the solid ones. It seriously doesn’t matter. You aren’t sacrificing anything here...

I get it. We all like splitting hairs and planning every detail about our cars. That’s why we are on M forum. But seriously there’s no difference. Just buy one

[old///MFanatic]

Condor's UHMW stuff has popped up in the E30 world a fair amount. I don't buy that it's this magical material that's as solid as aluminum but somehow absorbs vibrations.

Hit a chef knife on a professional culinary cutting board (similar material). Then hit that chef knife on an aluminum board.
Seems very possible it absorbs some vibrations that aluminum would not. No?

[r4dr]

If Condor Speed is everything aluminum is but absorbs vibrations, lighter, easier to install and less expensive. Seems like the logical choice over aluminum.

Condor's UHMW stuff has popped up in the E30 world a fair amount. I don't buy that it's this magical material that's as solid as aluminum but somehow absorbs vibrations.

[old///MFanatic]

You are overthinking this. Use this energy and time on comparing RTAB choices instead

Already researched that, fun stuff. Yeah I don’t really want that new topic in this thread. Figured since this was a subframe mount topic with others already in thread it could get new answers. Seeing nobody can provide info between aluminum and UHMW material I may have to make a new thread.
Why am I researching? I don’t have free access to a lift any longer so don’t want to do job twice. I want to make the best choice for my car and needs. If Condor Speed is everything aluminum is but absorbs vibrations, lighter, easier to install and less expensive. Seems like the logical choice over aluminum.

[heinzboehmer]

Very happy with the setup and will be repurchasing the CMP Rtab in the future.

Best thing about the CMP RTABs is that they use a lemforder (I think) bearing. So if it wears out you can just press a new one in. No need to get everything again unless it's for another car.

[SteelGreyM]

With seeing all the favorable replies to suggested use of solid mounts. (Thanks all for previous contributions/information)
I’ll just keep next question in this thread. I’m sure there’s things I’m missing. Thanks for any and all input.

*What are the largest advantages of:
Solid aluminum mounts vs. Condor’s (UHMW) mounts?*
Aluminum mounts: One piece design(less failure options), Solid no flexing, Some brands make shorter to compensate for plates.
Condor Speed UHMW material: Absorbs vibrations, Lighter weight, Top hat stability(?), Easier to install (tolerances in subframe), Cost advantage.

> Condor Speed Shop subframe mounts
https://www.condorspeedshop.com/coll...ngs-e46-e46-m3

You are overthinking this. Use this energy and time on comparing RTAB choices instead

FWIW I have CMP mounts on CMP plates. CMP Rtab as well (my favorite RTAB on the market). Very happy with the setup and will be repurchasing the CMP Rtab in the future.

[old///MFanatic]

With seeing all the favorable replies to suggested use of solid mounts. (Thanks all for previous contributions/information)
I’ll just keep next question in this thread. I’m sure there’s things I’m missing. Thanks for any and all input.

*What are the largest advantages of:
Solid aluminum mounts vs. Condor’s (UHMW) mounts?*
Aluminum mounts: One piece design(less failure options), Solid no flexing, Some brands make shorter to compensate for plates.
Condor Speed UHMW material: Absorbs vibrations, Lighter weight, Top hat stability(?), Easier to install (tolerances in subframe), Cost advantage.

> Condor Speed Shop subframe mounts
https://www.condorspeedshop.com/coll...ngs-e46-e46-m3