Do I need a poly diff mount to go with poly SFBs?

[Wishno87]

*shrugs* I prefer 100% solid aluminum lol.

Lol this is my DD but im young so I don't mind the extra responsiveness. Solid aluminum would cause the GF to break up with me though

[nando]

So you mean the "MZ3" is better than stock E30? This confused me.

MZ3


Stock E30

definitely.

*shrugs* I prefer 100% solid aluminum lol.

how many street miles a year you put on that thing? ;)

[Wishno87]

I was planning for 75d SFBs so you think the MZ3 will do the trick then? You think the two metal plates on each side make up for the lack of material on the top and bottom?

[nando]

reconsider 75D subframe bushings. they are going to be very stiff. not as stiff as solid aluminum, but close enough to drive you nuts on the street.

they probably used less rubber because the bushing is overall stiffer (and they used more steel instead). there has to be some give somewhere. if you try to move it in your hands you won't be able to.

[shiboujin]

how many street miles a year you put on that thing? ;)

a few thousand at this point. Drive the car to the track, beat it, drive home. It is a bit noisy but it isn't beyond a daily. I actually like hearing the feedback. Lets you know what the car is doing.

I was planning for 75d SFBs so you think the MZ3 will do the trick then? You think the two metal plates on each side make up for the lack of material on the top and bottom?

If you do 75d for the subframe, you need 75d for the diff. The MZ3 will 100% not do it.

reconsider 75D subframe bushings. they are going to be very stiff. not as stiff as solid aluminum, but close enough to drive you nuts on the street.

they probably used less rubber because the bushing is overall stiffer (and they used more steel instead). there has to be some give somewhere. if you try to move it in your hands you won't be able to.

I kind of agree. It won't make your car feel much stiffer. That's what your suspension does. But it will transfer more noise and make it SOUND harsher.

Are you going to track the car? If so, just skip the poly and go straight aluminum. The diff between 75d and aluminum isn't that much. If you want to street it, I'd stick in the A shore level of bushings like 90A max.

[Wishno87]

I thought 75D was the softest poly? Are MZ3 SFBs harder than stock E30?

[shiboujin]

nah look at the scale. A is softer than D.

[Wishno87]

Ahh sorry guys my mistake. 80A is what im looking for right?

[shiboujin]

If not tracking, then yes. go 80A and I suppose the MZ3 diff bushing or an 80A diff bushing.

[shiboujin]

Here. I made a decision tree for you.

[Wishno87]

lol I like that ^

But what if its a stancecar?

[shiboujin]

Hmm. That's out of the bounds of my knowledge. I would assume you would want as stiff as possible. Even the smallest thing could be the difference between hella flush and hella smashing up your fenders.

[Wishno87]

Hmm. That's out of the bounds of my knowledge. I would assume you would want as stiff as possible. Even the smallest thing could be the difference between hella flush and hella smashing up your fenders.

haha no kidding right? As far as TABs are there any slight upgrades I can make over stock E30 without going to squeaky poly there?

[shiboujin]

I run 75D delrin with no squeaks. Delrin is "self lubricating" while regular poly tends to bind. If it starts squeaking, shove some grease in there and keep going. Although, for a stance car, I don't think it's that necessary unless you have like 500whp.

[nando]

I haven't had any squeaks in 100k+ with IE RTABs, but the original version fits very tight. the TA moves about the steel center bushing, not the urethane. There's no reason it should squeak.

I believe newer ones are smaller (for easier installation - mine are nearly press-fit), which tend to move and cause squeaks.

delrin could be a good choice, as long as you didn't go too stiff on the subframe and diff. I don't really think the TA's will cause substantial increase in NVH since it has to also be transmitted through the subframe and diff bushing before it hits the body.