Hybrid Suspension compounds. Utter madness?

[Wishno87]

Im going to be replacing my suspension rubbers in a few months and i was thinking about running sort of a rubber/urethane hybrid in my rear suspension. I want to use urethane RTABs and rubber subframe bushings.

My reasoning for this is I want my rear trailing arms to maintain the same geometry during hard driving. I also dont want too much NVH in the cabin.

So my solution i though of was to use urethane bushings to maintain consistent trailing arm movements but use rubber in the subframe bushings to isolate that harshness from the body. That way the rear subframe is more uniform but I dont feel it in the seat of my pants when im just driving around.

So am i just completely ignorant to some blinding flaw in this idea or am i just crazy?

Any input from you seasoned vets would be great.
Thanks,
Josh

Yes my vert is that hardcore:D

[DCColegrove]

I don't see a problem there that is to say your logic if functioning alright.

[Wishno87]

One issue that i have considered is the trailing arm makes contact with the rest of the unibody though two ways. One is though the subframe but the other is though the spring and the shock. This could be a way that NVH could be transferred to the body but I do still have the spring pads installed so this shouldn't be a dealbreaker.

[jlevie]

That combination will work fine.

[Wishno87]

Any more input on this?

[asubimmer]

Any more input on this?

you already got your answer a few times

[smonkbmw]

you already got your answer a few times

how so? because colegrove said so?

im curious to know a little more of a informative response to this question besides "yeah it will work". it will work but how well? will these parts have issues being different compounds? will one wear faster that the other? stuff like that.

[asubimmer]

The trailing arms are different than the subframe/diff pair. The subframe and diff must be the same compound so that you don't break one or the other. The softer of those two would fail. Like if you had urethane subframe bushings and a rubber diff mount, then the diff mount would break off the rest of the diff. They work as a team you would say.

Now the trailing arm has nothing to do with them and any compund can be used between the two. Personally I have delrin subframe and diff mounts, and urethane trailing arm bushings. I would have used delrin TA bushings also but I had a set of urethane's around.

[smonkbmw]

ah ok, cool, thanks.

[Wishno87]

The trailing arms are different than the subframe/diff pair. The subframe and diff must be the same compound so that you don't break one or the other. The softer of those two would fail. Like if you had urethane subframe bushings and a rubber diff mount, then the diff mount would break off the rest of the diff. They work as a team you would say.

Now the trailing arm has nothing to do with them and any compund can be used between the two. Personally I have delrin subframe and diff mounts, and urethane trailing arm bushings. I would have used delrin TA bushings also but I had a set of urethane's around.

Thanks for that. This is the kind of nitty gritty tech response i was looking for.

So then i should be doing rubber diff and subframe then urethane in the TAs.

Urethane is softer than delrin correct?

[moatilliatta]

yes, id just do urethane everything, You wont notice to much more sound.

[asubimmer]

Thanks for that. This is the kind of nitty gritty tech response i was looking for.

So then i should be doing rubber diff and subframe then urethane in the TAs.

Urethane is softer than delrin correct?

Yeah urethane is softer than delrin, but its not nearly as soft as rubber. Delrin is pretty much a solid mount. I would reccomend urethane for 98% of the ppl out there. Its much easier to install than the stock rubbers and they aren't too harsh for the street. The only reason to go harder would be for a dedicated track car imo.

[smonkbmw]

/\ right and this is going into a car where the driver panics over any vibration, cowl shake etc. i was recommending all stock rubber to help combat this. advise?

[Stephen]

So by this logic, when i install my green IE subframe bushings, which are urethane, i should also replace my diff mount (currently stock) with a comparable urethane bushing?

[Liam]

The short answer is it will work fine and nothing is going to break.

The long answer is that using harder bushing materials is going to transmit more road noise to the cabin (less so with the trailing arm bushings) and make the suspension less compliant.

None of this will affect the cowl shake on a C, that is caused by something else.