Polyurethane bushings?

B

backformore

New member
Someone stated on another forum that poly bushings should be avoided because the deform under racing loads and do not return to original form like rubber. This is the first time I've ever seen that opinion but I wanted to see what the experts here thought.

Opine away.
 
it is true, and they wear out in time as a result. not a bad option in many cases given the price and alternatives, and they are almost always less compliant than the stock rubber, which is usually better. decent "first step" choice. keep them lubed.
 
Keep in mind how the bushed joint goes through motion as well. Many times, the compliance of the rubber is used to allow deflection along axes other than that of the bushing, and changing that compliance can create binding, which drastically affects the effective spring rate. This is even worse when you use a single axis bearing or solid bushing when a spherical is needed.

I'd suggest Delrin (nylon) for the applications we see, if you can't go metallic. There are also nylon-bushed sphericals if you need those. I'm not sure what sizes are available in those, but I'd check under the names Del-sphere and Roto-joint.
 
note, thoguh that a delrin bushing works less well than a polyurethane one when the motion is other than single axis rotation.

backformore, what car? Honda? avoid poly rear traling arm center bushing. get new OEM or Mugen rubber (I've heard they are now the same) the rest you can use poly no problem on 92-00Civics and DC tegs. 88-89 civic/CRX and DA teg there's some compliance in the front end, sphericals or stock there thoguh the poly will work for a while.
 
backformore said:
Someone stated on another forum that poly bushings should be avoided because the deform under racing loads and do not return to original form like rubber. This is the first time I've ever seen that opinion but I wanted to see what the experts here thought.

Opine away.
Click to expand...

Yep that's right. Have to look at a number of factors though as others mentioned. In some areas fine, in others not. IMO bad for anything that sees either big deformations or any rotating stress on it. Higher durometer rubber is better in many applicaions, and plastic or metal if forces are in a single plane with controlled motion... Depending on the application, I have just made my own from delrin.
 
spherical bearings are now SPECIFICALLY allowed, have been for a few years.

+1 for Chris @ kingpin. He makes some of the nicest looking spherical inserts and spacers I've ever seen, and has designs doen for most of the popular hondas.
 
OK , I'm going to ask a " dumb " question

Just how much of a difference do sphericals make on a car ?

Looks like the next step on my miata , but my checkbook is getting thin from the development process.
 
TStiles said:
Just how much of a difference do sphericals make on a car ?
Click to expand...
They're an "nth degree" thing on the scale of all the stuff you want to do. Springs/shocks/swaybars are all more important. Sphericals' primary function is to reduce the flex and movement (to improve geometry) and to reduce "sticktion" so your shocks and springs are more repeatable and consistent. In some limited case (e.g., Nissan 240SX) they allow a larger range of unbound movement, but for most cars that's not such a big deal.

Sphericals "can" make a big difference, but IMO only once you've taken care of all the big stuff first.

GA
 
+1 for what tGA said. When using poly in my suspension, it would be typical for the suspension to act one way at the start of a session, different at mid-session and very different at end of session. No braking, no turn-in nor apex point was the exactly the same since the poly would flex differently throughout the session. Again, we're talking nth degree here, yet noticable and as I changed bushings, my times have dropped.

FYI, I run solid bronze PCI bushings up front, PCI spherical for the rear trailing arm and Progress LCA in the rear.

http://www.kingmotorsports.com/p-1064-pci-bronze-bushing-kit.aspx

http://www.kingmotorsports.com/p-1060-pci-spherical-trailing-arm-bearing-kit.aspx

http://www.progressauto.com/product...ear/1992/make/Honda/model/Civic/productID/282

PS. I run just poly at the shock mounts. Happy shopping!
 
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Greg Amy said:
They're an "nth degree" thing on the scale of all the stuff you want to do. Springs/shocks/swaybars are all more important. Sphericals' primary function is to reduce the flex and movement (to improve geometry) and to reduce "sticktion" so your shocks and springs are more repeatable and consistent. In some limited case (e.g., Nissan 240SX) they allow a larger range of unbound movement, but for most cars that's not such a big deal.

Sphericals "can" make a big difference, but IMO only once you've taken care of all the big stuff first.

GA
Click to expand...

That's consistent with my understanding , Thanks for the confirmation.

A couple of other thoughts I would welcome feedback on :

- getting rid of the rubber bushing on a shock has more value than on a control arm that has good geometry ( miata )

- The jump from good stock bushings to poly bushings is just not that big of a deal ( I did it on another miata and the impact was insignificant ) but the jump from stock to sphericals should be a significant step in improving repeatability , turn in , corrections , getting shocks dialed in , ect.

- Adding sphericals to a miata is going to be the biggest thing I can do to get that " formula car feel " that I miss ( FC & SRF )

Thoughts ?
 
Thanks for the input. Sphericals are not in the current budget. Very early stage of development (like ground zero). Probably stick with stock bushings now and focus on some areas of larger gain.

Car is a 00 Civic Si for those that care
 
Chip42 said:
note, thoguh that a delrin bushing works less well than a polyurethane one when the motion is other than single axis rotation.
Click to expand...

Chip- yes, and thanks for that clarification.

Does anyone in IT use the Delrin-caged sphericals? It's a somewhat acctractive thought, as they are rebuildable on the cheap. The stub-struts on the rear a-arm mounts in my Charger are in need of some, um, better control I think, and I'm contemplating my options...
 
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