Chibo

I should see him next weekend, I'll ask.
I assume they just have no give so a decent curb hit or anything transmits the force right to the now-weakest-link arm, whereas rubber would just flex and absorb the big initial force.

It depends on how they are positioned in the car... for example, the rear trailing arm bushings in the E46 BMWs should stay OEM otherwise you have strange handling characteristics (big grip falloff all at once) since the trailing arm bushing is meant to articulate a bit; poly causes binding. BMW calls it elasto-kinematics (I shit you not, how German).

treimche

Real world experience is great to hear. Thanks for sharing. I have used poly engine mount inserts on cars in the past and they definitely stiffened things up. It seemed after some time, they would squish some so that they were easier to remove/reinstall. Not sure that is a desirable characteristic in the suspension though. What are your thoughts?

Fokker

Depending on positioning, poly can start to soften/fail if it sees too much heat. I've seen numerous failed S2000 poly bushings on the passenger side (exhaust side). I have been using poly inserts on the torsional mounts in my MR2 for years now and they don't feel any softer on inspection nor in performance; the trailing mount is close to the exhaust, but not the header. I have also been running poly on that car for many miles and haven't noticed any detrimental handling changes (MacPherson strut front and rear).

B serious

I've used poly on 2 different cars. Energy suspension full kits.

Compliance bushings shouldn't be solid poly. Its such a terrible idea.

Poly doesn't last as long as rubber (in terms of a bushing or engine mount material). Before refuting this....read the part where the OP has 150K on his factory rubber bushings on his car from the early 2000's.

I found poly very harsh and rattly. Likely due to the fact that they have *some* slop and experience tons of friction during use. No confidence.

Not saying cars with poly bushings don't make a great budget track car application. But that's all I would consider them good for.

If poly was so universally fantastic...then why would OEM's that make performance cars use rubber and/or sphericals which are much more expensive? Why wouldn't they use poly?

Car Analogy

Well lubed poly doesn't have much friction. But they do have significant stiction. Static friction. That resistance to initial movement. So if its a big bump, that easily overcomes stiction, the extra free moving travel of poly tends to be more compliant and comfortable than rubber. But for little bumps, that static friction makes the poly act more like a rubber bushing, except way stiffer and adding way more spring than rubber does. In other words, horribly stiff, uncomfortable suspension. For bumps somewhere in between, that don't have the sudden, sharp impact that overcomes stiction, you get initial super stiff extra spring effect from the poly, until enough force to overcome the stiction, then much more compliant than rubber.

In other words, very inconsistent and unpredictable suspension response.

If you are driving hard on uneven pavement, poly might actually work pretty good, since you'd have a lot of hard, sharp impacts that would blow past the stiction, and you wouldn't notice it much.

imstimpy

I did Challenge Delrin offset bushings in the front upper a-arms (wanted more camber), Hardrace hardened bushings in the rear upper a-arms (couldn't stomach the Mugen cost), then Mugen for everything else. After about 1.5 years I wanted the compliance back so I bought all new arms.

I'd be happy to sell the full AP2 suspension arm set if you'd rather save yourself the headache on doing the bushing job. The arms have about 36,000 miles on them and the bushings have about 5,000 miles.

treimche

That would all depend on the price. I really don't need another whole set of suspension arms though.

BuggyofMildDiscomfort

I build off-road racers and we avoid them anywhere we can unless we have no choice (because of articulation levels needed) - the stiction and friction is an issue even with big impacts, more so, in fact, as our cars are very hard on damping and softer sprung than track cars, so the friction changes make a relatively large change - and even worse, they wear rapidly as contaminents get into the bush - not an issue with twisting metalastics.
And even on a large hit they have far, far more friction than a twisting rubber bush (which just has internal damping through heat generation).

Car Analogy

Good to know!

Watching on TV you can easily see how all those high suspension travel off road vehicles have comparatively soft springs, the way they articulate and absorb big landings. It makes sense they have softer spring, and stiffer damping, than short travel on road suspension.

It also makes sense how poly would not work well in that arena. Also how poly needs sticky lube, and its unsealed, how that would be a recipe for wear in that environment.

BuggyofMildDiscomfort

Yes, I spend quite a bit of time where we do have to use poly reaming them out for a perfect fit and shaping the ends to form lip seals to keep the dirt out - doesn't stop it completely though. Poly really isn't a good bearing material for cars, great as a bush for absorbing shock, poor as a bearing.