Help with Suspension Refresh at 50k miles/10 years

[slater]

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.

the vorshlag article does touch on it, they state in the first paragraph (going from memory here) that the rear trailing arm rotates in more than one axis.

if it helps, think of how the rear trailing arm rotates as the wheel moves up and down. rubber (sans limiters) allows this movement, but at a cost of reduced lifespan (and toe change, since they are soft). limiters, and poly, will limit movement and ultimately bind. only spherical will allow full, unencumbered articulation, without toe change or slop.

peter

[rkneeshaw]

Peter, I agree.

I was saying the vorshlag article gives the impression that poly is a bad choice, and limiters are a good choice. My argument is that they are the same in regard to how they effect the articulation of the rear trailing arm.

Would there be any drawbacks with spherical RTABs? I thought someone mentioned more maintenance, but what kind of maintenance would there be?

[slater]

Peter, I agree.

I was saying the vorshlag article gives the impression that poly is a bad choice, and limiters are a good choice. My argument is that they are the same in regard to how they effect the articulation of the rear trailing arm.

i agree 100%.

Would there be any drawbacks with spherical RTABs? I thought someone mentioned more maintenance, but what kind of maintenance would there be?

no, from what i've read, there is no drawback - just a more precise and communicative rear end.

as for maintenance, you can see here from the pic on their website that it uses what is potentially the same sealer spherical bearing that we have already in the rear hub for the upper/outer rear control arm mounting point. it is sealed and should really never need replacement, but if it does, it's an OEM part. that's what makes it so attractive to me. (you know - i just thought of this - i have a new pair of those OE hub/control arm spherical bearings on the shelf, i will check today to see if they are indeed the same as the ones in the bimmerworld kit.)



here are some quick thoughts from someone who uses them that i found - and i would echo his sentiments about the poly RTABs:

http://www.bimmerforums.com/forum/sh...4#post28312424

peter

[rkneeshaw]

...it uses what is potentially the same sealer spherical bearing that we have already in the rear hub for the upper/outer rear control arm mounting point. it is sealed and should really never need replacement, but if it does, it's an OEM part. that's what makes it so attractive to me.

Dude, I like! What a great design, using the existing spherical bearings from the rear control arm inside a "carrier" of sorts.

Reminds me when I upgraded the lower outer rear control arm bushing to the spherical bearing (it's what the M3's use, and is a slight upgrade for non-m's), that also uses the exact same part too.

When do you get yours installed?

[slater]

Dude, I like! What a great design, using the existing spherical bearings from the rear control arm inside a "carrier" of sorts.

Reminds me when I upgraded the lower outer rear control arm bushing to the spherical bearing (it's what the M3's use, and is a slight upgrade for non-m's), that also uses the exact same part too.

When do you get yours installed?

yep, and i am putting some of those in the lower rear outer control arm location as well. hopefully early next week at this point, i have about 4hrs of time tomorrow and then not until monday night. i need to get the entire rear end dropped and center driveshaft out too (lots of maintenance going on ).

peter

[Vas]

It is a great idea but have to bite the bullet at $200 for some RTAB.

[slater]

It is a great idea but have to bite the bullet at $200 for some RTAB.

$200 vs $80 for powerflex or lemfoerder M3/Z4M... peanuts for better handling.

peter

[Vas]

$200 vs $80 for powerflex or lemfoerder M3/Z4M... peanuts for better handling.

peter

$40 for z4m rubber

[UdubBadger]

z4m is the legit way to go to retain daily comfort

[NoVAphotog]

z4m is the legit way to go to retain daily comfort