I have an answer
First of all the plastic is UHMW which stands for ultra high molecular weight and means that it is super dense which makes it perfect material for a solid bushing. It is similar to Teflon but heavier and more durable als less seceptable to temprature changes.  Most of the time when people are rollerizing their front end it is because they are eliminating rubber bushings,such as the idler arm, spring perches, control arms or strut rods.  In those cases the rub not only flexes the way the designer intended by allowing the parts to move as designed but also flexes in other directions which makes the handling more sloppy.  With the UHMW bushings on a jag, the bushings are just as solid as the bearings so unwanted motion is not an issue like it would be with rubber.

Basically the UHMW bushing functions just like the bearings, has the same life span as the bearings,  but has the added advantages  over bearings of:

easier install especially at the hub
less expensive
maintenance free (bearings need to be greased, but the bushings don't)

I have taken some UHMW  material to the machine shop to have a couple of sets machined up for hubs so let me know if you are interested in a set.

I am not sure yet because I still am weighting for the machine shop to get them done.  I am hoping some where between $60.00 and $70 for a set of 4 hub bushings.  It is really going to depend on the machine shop costs as I don't plan on making more than a couple of bucks per set.

I have two identical IRS units in near identical cars but very little use yet on either one. Both have been in the cars about a year. One has bushings, the other OEM bearings. Currently the suspension on the bushed unit is very stiff whereas the other one is free. I expect this to change once we are driving the car regularly but it does bring up one particular difference between the two. The interesting thing is that for the past 6 months the bushed car has been away for bodywork and paint and when it came back the rear suspension was very very stiff whereas the other moved freely. We put it on the lift and unbolted the coil over from one axle and the upright was difficult to move up and down, noticeably stiffer than when the car went out. Since UHMW Polyethylene does not absorb water to my knowledge I would have to attribute the increased stiffness to slight surface rust on the shafts. The only other thing that seems remotely possible is dust from the bodywork and it's hard to see how that could have gotten in there. Anyway, just another consideration. Incidentally, I doubt anyone has done an actual stress analysis on the stuff but I've done a lot of work with UHMW and I do not believe it to be as rigid as steel bearings. Delrin might be pretty close but it tends to squeak. I put the steel bearings on my car. When I do get around to the next LCA design I will consider alternatives but we'll just have to wait and see where that leads.

JB

Last edited by Jim Blackwood (5/05/2011 5:19 am)

The machine shop is finally working on my bushings and I should have them before to long (couple of weeks)  the original CWI kit (CWI is no longer in business) replaced the hub to wishbone bearings and the hub to differential bearings.  in most cases the hub to differential bearings are reusable so I will be offering just the hub to wishbone bushings.  By using them it takes less parts and there is no preload to set.  The CWI bushings in question are the white ones in the lower right hand corner of this pic

Last edited by Daze (11/09/2011 8:14 am)