Help with Suspension Refresh at 50k miles/10 years

[rkneeshaw]

That vorshlag link is missing the same point that I think the rest of you are.

Have any of you looked at that bushing once the limiters are installed? That thing isn't moving side to side or twisting. There's no difference from when you install a poly bushing.

The only difference between a poly bushing and a OEM bushing with limiters is the forward-to-rear movement of that rear trailing arm will be a little less "cushioned"... because the poly is harder than the rubber.

EDIT: btw, I've had both. I started with stock bushings and limiters, then installed the powerflex poly's. No detectable change in NVH. What I did detect was how planted and controlled the rear of the car was because those rubber bushings (even with the limiters) had gotten soft.

[Vas]

That vorshlag link is missing the same point that I think the rest of you are.

Have any of you looked at that bushing once the limiters are installed? That thing isn't moving side to side or twisting. There's no difference from when you install a poly bushing.

The only difference between a poly bushing and a OEM bushing with limiters is the forward-to-rear movement of that rear trailing arm will be a little less "cushioned"... because the poly is harder than the rubber.

EDIT: btw, I've had both. I started with stock bushings and limiters, then installed the powerflex poly's. No detectable change in NVH. What I did detect was how planted and controlled the rear of the car was because those rubber bushings (even with the limiters) had gotten soft.

I have not seen the bushing with the limiters installed. But I was under the assumption that the bushings wear out due to the extra space in the arm. So with the limiters installed, you are getting rid of that space which limits the bushings movement and extends the life of it.

[rkneeshaw]

I have not seen the bushing with the limiters installed. But I was under the assumption that the bushings wear out due to the extra space in the arm. So with the limiters installed, you are getting rid of that space which limits the bushings movement and extends the life of it.

That's what I thought too, and what Turner told me when I bought them back with 33k on the car in 2009. Rear end was feeling slippery over bumps and such at about 95k (last year) so I went poly. Made a big difference, handling was restored.

I just figure rubber is rubber, its going to age and crack.

[rkneeshaw]

I didn't read the whole thread yet, so I dont know how it turns out, but you can see what the limiters look like installed:

http://www.m3forum.net/m3forum/showthread.php?t=339709


There's no movement left.

Just like the poly RTABs:

[Vas]

That's what I thought too, and what Turner told me when I bought them back with 33k on the car in 2009. Rear end was feeling slippery over bumps and such at about 95k (last year) so I went poly. Made a big difference, handling was restored.

I just figure rubber is rubber, its going to age and crack.

That sounds about right. 60k is usually the lifespan of those bushings.

Correct me if I am wrong, but even with the limiters, does the bushing still twist inside of itself since its rubber and not poly?

[rkneeshaw]

Correct me if I am wrong, but even with the limiters, does the bushing still twist inside of itself since its rubber and not poly?

I don't see how that matters, because the metal arm goes AROUND the bushing. The limiters don't allow the big O in the arm that holds the bushing to twist in that mount.

What you can't see well in that vorshlag picture above, is that it is solid from side to side. There is thin tab of rubber between the limiter and the rear trailing arm. And when they are installed, there's no twisting movement there.

In fact, looking at these pictures, I'll argue that the poly bushing has more room to twist than an OE bushing with limiters. There is actually nothing on the sides of the poly bushing, only the firmness of the poly bushing is going to restrict twisting.

I believe Vorshlag posted that article because they dont make poly bushings. They do make limiters.

[Vas]

I can see the benefit of the bushing not moving side to side using the limiters. AS long as it does not mind. Also toe changes with suspension travel i believe.

[BMWCurves]

I can't speak to the difference with or without the limiters since I had them installed with the new Z4M bushings, but for $50 I'm not too bothered if they're not doing anything particularly useful other than being beneficial in my mind. That said, the new set up makes the rear feel much more planted than before.

[rkneeshaw]

For the record, I'm sure the limiters are fine, and I'd still run them if I didn't have poly. I'm just saying the argument that the limiters are better than poly RTABs for suspension articulation is flawed.

I'm interested to hear slaters feedback on the spherical ball joint RTABs.

[bimmergofast]

What shocks/struts are you going to use?

I picked up the Koni Yellows