Why isn't Polyurethane a good bushing material?

[PewterBird]

This is taken froma link in the Technical Database, Can anyone else support this?

Dispelling other myths:

Why isn't Polyurethane a good bushing material?

* "...virtually no deflection..." (cut and pasted from their web page). As mentioned above, the engineers that design these cars employ rubber bushings because deflection is required in most locations.
* "But I lubed them well, or I used Polygraphite® bushings": You are asking the poly material to act like metal bushings, and it can't. Lubing will temporarily reduce the squeaking and stiction. The graphite-impregnated versions are just 'pre-lubed', and once the graphite has worked its way out, the bushings will squeak and require regular lubing like the others. Lubing does nothing for the binding problem.
* "They get quieter over time": Poly will cold-flow, meaning it will deform under pressure and not return to normal, as it lacks the elasticity of the rubber bushings. Over time, they will loosen and then rattle. Check out the shape of your swaybar's poly end-link bushings after only a few months. This cold-flow issue can also lead to alignment problems on the front control arms, as the bushings deform.
* "But everyone sells them". Well, yes, and the manufacturers of Slick 50 and the makers of 'ultra/super white' bulbs could line up a long list of satisfied customers, but what would that mean?
* "Testimonials are everywhere!" but they don't convey the facts. Don't' believe everything you read in a glossy brochure or web page. Ever watch those late night infomercials? Like those other automotive miracles, wouldn't the large manufacturers pick up on this stuff if it really lived up to all it's claims?
* "But lots of other people use them!" As mentioned above, trailing arm suspension requires deflection in order to work, and when poly bushings are used, the required deflection is still there -- in the bending of the arms, mounting points, and flex of the rear tires. This is why these bushings appear to work fine for street applications.

[95Batmobile]

I thought poly bushings were better for handling because of their stiffness?

I wonder if that stuff is true, it might be what is rattling on my car and I can't find LOL
btw, jeff, come to my party feb 4th.

['94firebirdv6]

i was under the assumption that rubber was used in stock parts because of ride quality and quiteness. Poly was better than rubber and metal solid bushings were better than poly.

rubber > polyurathane :rolleyes:
i guess a lot of race car drivers and engineers were wrong too

[Dominic]

Poly bushings are hard plastic. They do not give like a nice rubber bushing does. Some places such as swaybar endlinks benefit from the poly bushings, but other places like LCAs and transmission mounts do not benefit because they end up binding and transmitting a lot of noise into the car when rubber does not.

Rubber is by far a better "bushing" than poly or heim.

[BirdOnFire]

i actually just changed my front lower control arm bushings because they were shot, i replaced them with poly bushings, but i noticed that the bushings are making a kind of creaking noise when ever i go over a speed bump at slow speeds or i am jacking the car up i hear it? is this because they are new, will the noise go away once they are broken in?, i also sprayed them with white grease and still makes the noise, also does anyone know what the part number is for the front lower control arm bushings are, from GM? becuase i would really like to change back to rubber.

[FirebirdGT]

It's in the Tech Database because it is the Truth. Try reading the otherlinks too.

[V6Bob]

One issue is specific to lcas. The lca bushings do need to twist slightly as the car rolls. Draw a picture and you'll see it. If poly is used at both ends of the lcas, when the car rolls they will bind up the rear suspension and make it not properly responsive to bumps - not a good idea.

[Little G]

i have rod-ends and love them, so there.

[oil pan 4]

So what should we use, rubber or poly bushings?
My rubber ones were all most squished through on the frount LCA's.
I bet you will feel the road more when you switch from old *** rubber to fresh poly bushings.

[PewterBird]

It seems that certain suspension parts require a bit of deflection and give in their bushings and others do not.

As it applies to Endlinks and Swaybar bushings. I would imagine less deflection of the bushing is good, because it will transfer that motion to the sway bar. Which is designed to fight flex, and keep both wheels flat on the ground.

Where as I would think that a poly tranny mount would be bad, because it will not bend and give in to the twisting of the tranny. Then it would tranfer the force directly to the crossmember.
And that would almost defeat the point of the mount.

[T-Punk]

i agree with the tranny mounts and motor mounts too as there is no purpose to use poly in those apps... at least not that i can think of. as far as actual suspension parts though i really do like poly.

[memphis_raines]

Originally posted by T-Punk:
rubber is better for the average driver. Poly is great for those of us the like to feel the road and like stiff suspensions. I personally love poly.

I agree. I have poly/poly BMR lca's and panhard rod, a prothane TA bushing, and a 1LE front swaybar with prothane bushings and endlinks, and it's great. I don't know where people come up with this stuff about the noises though....I've never heard any kind of noises from it.

[Den69RS96]

Where are the facts that prove rubber is better than poly in terms of better performance? I won't argue that rubber is better for ride quality, but how is it better for performance? Why do race cars use poly, or metal bushings and rod ends if rubber is superior?

[oil pan 4]

I don't like driveing on jello so I'll stick with poly.
The rubber motot mount bushing for my Z28 was gone about as soon as I started driving it. So I won't use them on a v8 any more.

[Dominic]

Bushings are meant to isolate noise, vibration, and allow parts to still move with some freedom.

Poly isolates little noise, little vibration, and reduces part movement to one axis when well lubricated. I can assure all of you, poly is no better than a *hard* rubber component. The soft stock rubber in stock LCAs is pathetic, for example, but rubber is what allows a car to not only HANDLE well but also RIDE well. If you go poly, you'll lose the ride, and probably not gain a whole lot of handling.

Im talking street cars here too, if anyone wants to get into a discussion about race cars, they can ALSO forget poly because they typicall run all rod-ends where bushings would normally be. Why is this? Rod-ends are zero bind zero deflection joints!