Are Current OE Rear Subframe Bushings Improved?

[LSBNick]

Been on solid subframe bushing with monoball SDW RTABs and oe diff bushings. No added NVH at all and the car feels super solid.

[old///MFanatic]

UHMW (what Condor Speed Shop has been making) is a stone's throw away from solid, I don't understand the hesitation in just getting solid mounts? All M cars starting with the E92 GTR and F8X cars have the rear subframe solidly mounted, and most people I've seen post their experiences switching to solid mounts say there's no NVH.

Yeah thanks for input, much appreciated. I get these are just a one step from complete solid. I mentioned it as he’s also in the solid (semi) mount camp, as you all are.
My overall hesitation is the “impact stress” solid produced to the mounting area. I do not want to have to install a full top mount bracing to alleviate the damage often seen after solid mounts.

E92 GTR and ///M F8x chassis cars have very different subframes footprints. It was designed that way. It’s what in business we’d call two different animal designs. Saying went something like “Don’t expect wings of an eagle put on a swallow to work better because they do on the eagle”.

[old///MFanatic]

There is no nvh when switching to subframe solids IF, all your other bushings from moving components that attach to the subframe are stock rubber.
I would add that, because solids increase localized stresses, it is recommended that solids are put in cars with additional reinforcements (topside kits for front and rear mounts, not just underside plates).

My main concern is removing the firmer ///M mount design that is still designed to absorbs the impact stress. That is main concern.

Also NVH evaluation is usually associated with car rolling (idling). Most have forgotten and just use to the M clunk. Curious, are you able to comment that with solid that has not increased in chassis going from rubber M mounts to solid? One might expect that increase over stock M rubber mounts. Sure it’s a non-issue for track car, but would think street car one might not want that increase. Interesting to get some feedback on that from those with. Much appreciated.

[HighOnLSB]

Another street car on solid subframe and monoball RTABs. No increase NVH while driving or in regards to M-clunk.

[Slideways]

For anyone who has installed solid subframe bushings, are the two front bushings supposed to contact the hex on the subframe mounting stud or the RACP sheet metal?

CMP changed the design slightly to match other solid bushings which seem to contact just the hex portion of the subframe stud. The previous CMP bushings had a machined portion where the hex slotted in:




Edit: CMP replied saying that both older and newer style bushings only contact the hex portion on the front subframe studs. The redesign helped with manufacturing costs and made the bushings 15% lighter in weight.

[Ianb]

When I made mine, rightly or wrongly I made them to touch both the hex spacer and the bodywork (reinforcement plate) so the bush had a recess in the top exactly the depth of the hex, thinking best to spread the load over the reinforcement plate and also the stud through to the upper reinforcing/brace.

[Epsilon]

For anyone who has installed solid subframe bushings, are the two front bushings supposed to contact the hex on the subframe mounting stud or the RACP sheet metal?

CMP changed the design slightly to match other solid bushings which seem to contact just the hex portion of the subframe stud. The previous CMP bushings had a machined portion where the hex slotted in:

Very nice observation! It would be interesting to find out from CMP why the design change.

[old///MFanatic]

^ If I read the CMP website correctly they redesigned their solid bushings to raise them.

If the car these bushings are fitted to has been lowered ~13mm, (1/2”) or more, you’ll find that the change in rear camber from both is equally opposite and you'll remain roughly in the same range of adjustment as before. To be clear, the need for adjustable camber arms when fitting these bushes only exists when the car is still at stock ride height.

[Slideways]

CMP replied saying that both older and newer style bushings only contact the hex portion on the front subframe studs. The redesign helped with manufacturing costs and made the bushings 15% lighter in weight.

[Slideways]

One more thing I forgot to ask about the solid raising bushings (slightly raising the subframe), is there any concern with the driveshaft angle relative to the diff? Hopefully, that will not impact the service life of the driveshaft, CSB, diff or diff bushings.

[r4dr]

One more thing I forgot to ask about the solid raising bushings (slightly raising the subframe), is there any concern with the driveshaft angle relative to the diff? Hopefully, that will not impact the service life of the driveshaft, CSB, diff or diff bushings.

Wouldn't raising the subframe put it back in the position it was from the factory?

If the reinforcement plates push the subframe down by the thickness of the plates, and the bushings raise it back up to correct for the plates...

[Slideways]

Wouldn't raising the subframe put it back in the position it was from the factory?

If the reinforcement plates push the subframe down by the thickness of the plates, and the bushings raise it back up to correct for the plates...

Yeah, but the CMP document also stated something about correcting the suspension geometry for lowering the car.

[old///MFanatic]

Wouldn't raising the subframe put it back in the position it was from the factory?
If the reinforcement plates push the subframe down by the thickness of the plates, and the bushings raise it back up to correct for the plates...

Plates add material. Like if you added washers on top of the raised bushings. I don’t see how that would make it even out.
Diff carrier would be lower from the body and diff driveshaft geometry makes sense should be altered some.

[r4dr]

Plates add material. Like if you added washers on top of the raised bushings. I don’t see how that would make it even out.
Diff carrier would be lower from the body and diff driveshaft geometry makes sense should be altered some.

Yeah, but wouldn't the plates add material in the opposite direction that the bushings would be raising the subframe? I don't think "raised" subframe bushings push the subframe farther down?

[Tbonem3]

Raised refers to the subframe going up higher (closer to body), back to stock height even though you have plates.

Doing this puts you back in stock camber adjustment range (with stock chopsticks)