RU4L98

While driving home yesterday I was pondering the correlation between broken Rear Suspension/Drive Line parts and the usage of Poly Bushings!

I've read a few posts were people stated that they thought the Poly-B's weren't allowing enough movement of the suspension components. This cause's a Binding action (inducing greater bending moment forces/side loading) of the suspension. Also there is much higher peak shock loads being developed in the Suspension/Drive Line by the non-compliant Polyurethane material.

So I pose this question:
Do you think the benefits of using Poly Bushings, are actually the very thing that's greatly contributing to Rear End/Drive Line failures in high performance vehicles?
I'm starting to!

Chris

h rocks

What are the specifics?? What's breaking that leads you down that logic trail? The short answer is no. Tell us more.

RU4L98

Hi h rocks, well luckily nothing out of personal experience, but rather reading all the posts about "I just broke ~" in the rear end. Maybe BrianCunningham will cut in here, the dynamics of any suspension are extremely difficult to fully conceptualize.


The forces generated by Tq-Vs-Suspension angle/velocity, and interrelations to the myriad of ground surfaces/driving conditions, is WAY TO BIG for my pea brain. But, by using simple physics here, it's pretty clear that substantially high peak shock loads, bending moment(s), member deflection(s), and a host of other Suspension Nasties, are being induced by the use of Poly Bushings.

Just look what happens when someone uses solid engine/trans mounts, or metal heim joints/solid bushing on a street driven vehicle- accelerated ware/failure.




[This message has been edited by RU4L98 (edited 07-27-2001).]

No Go

I do agree that some poly bushings cause more friction at certain points(rear lower outer camber rod juncture comes to mind) but it seems nearly all suspensions include some friction to help slow suspension movement not including the shock absorbers-for instance serations on rubber bushings on my old Nova for example. If one were to remove the serations on the car it nearly becomes undrivable due to suspension moving too freely.

That is my opinion of course, but the rear poly camber rod bushings have been doing fine for last 11,000 miles and seem to have simply made the rear end tighter.

SouthernSon

Would not the poly bushings help keep things in better alignment and therefore prevent sever angles of torsional momentum?

Aggravated4life

I dont think there would ever be a problem with breakage with poly bushings.
I have a 86 and just re-did my rear end set up with all new ploy type bushings.

For 2 years I was driving on metal on metal...the bushings in the back were practically missing where the bolt holds them together..the ride was awful.They were still there inside but not in between 2 ajoining parts.

Nthing ever broke that entire time and now with the new bushings in the rear, the car feels 100% better..I plan to do the front suspension this fall.

maybe if you jump the car a few feet off the ground and break something I can see that but I just cant imagine someone pushing their car hard enough on the street or track to break something as a result of the bushings...

Usually with the drag races, people break half shafts,U joints and knuckles before their bushings and bolts pull apart.
Thats what I gathered here...
at least so far after 2 years.

If someone lives where the roads are always bad, Like a big city or something, id suggest to stay with the OEM rubber bushings for that kind of driving.
Not out of fear something will break if poly bushings were used instead but for ride quality.

Is there a first documented case here that poly type bushings caused early failure in suspension parts?
If so id like to know and learn about it.

h rocks

RU4L98, I think you are looking for lions and tigers and bears, and there's only Goldilocks in the woods. I have run all of your cited examples with nothing but positive results. But it's not a "one size fits all" situation. I currently run mostly poly with a number of exceptions. Notably, the camber arms and trailing arms arm Heim jointed, and in my front control arms I installed hybrid aluminum and Delrin bearing type bushings. All the changes that I have made over the last four years have done nothing but improve the handling accuracy of the car. If you want any help on the specifics let me know. PS. solid engine mounts are solid, poly is still flexible but has a very high durometer value.