Next step is to install the Polybronze bearings. Polybronze is actually a bronze bearing that rides on a steel race fitted to the spring plate. The bronze on steel provides a precisely machined low-friction bearing action that never squeaks and can be re-lubricated.
This picture is of the prototype set that has been adapted from 911 parts. Four of these are used. Production parts will look the same, except the grease grooves will be positioned differently.
The bronze is surrounded by a polyurethane jacket. The polyurethane is not part of the friction surface, its purpose is to accommodate irregularities in the factory mounts. Because the bronze core is rigid, the poly jacket can compress slightly for irregularities without pinching the bronze friction surface.
The product has been available for 911s for about a year. They are the hot ticket performance wise and with none of the troublesome fitment issues and squeaking that plague regular polyurethane/delrin type bushings.
The races are fit to the spring plates. Springs plates vary slightly in diameter (one reason regular polyurethane bushings are so hard fit properly). To accommodate the variation, shims are fit between the race and spring plate to make it good and tight. The shims are included with the product. The race provides a precisely machined surface for the bronze bearing to ride upon.
Above pic shows the spring plates with both races installed and bearings slipped on.
Press the bronze bearings into the spring plate covers using bench vice or press. Liquid soap is used to lubricate the polyurethane to ease insertion.
Once pressed in, drill a hole for the grease fitting. A small pilot hole is first drilled fully through one side of the bearing. A large hole is then drilled and tapped in the aluminum cover plate to accept the grease fitting.
Pic above shows the grease fitting and installed in the assembly.
And the back side of the assembly.
Next install bearing in the torsion tube.
Clean up the ID of the torsion tube using sandpaper and scraping tools. The ID tends to have hard residue from the rubber bushings, this must be removed to get a good fit.
Lube up the bronze bearing with liquid soap and insert it into the cleaned up torsion tube. Then use the spring plate cover plate and a block of ½ wood to press the inner bearing into place. Tighten the 4 cover plate bolts in sequence to push the bearing in.
Next drill the torsion tube for the grease fitting. Again, using a small pilot hole through the bearing then a shallow larger hole tapped for the grease fitting.
That's it for part 2. Part 3 will show re-installation of the spring plates and torsion bars.
Click for part 3