Schwinn Sweetspot generations

History of Sweetspot generations as told by former Schwinn employee Rich Adams:

Here's how I remember it: The first Castellano bikes used the smaller diameter sealed bearing, so the seed was planted within the design group that this was the way to go. Also, I recall discussions about reducing stiction, and trying to coax more small bump sensitivity out of the URT design. Hence the sealed roller bearing were the first designs out of the gate. Simultaneously with the development was the standard suite of lab tests to evaluate strength and rigidity, as well as a fair amount of on-trail testing as well. While it was a long time ago, I recall there being some discussion about how whippy the back end was in hard cornering... which got the wheels turning about how to mitigate that problem. Through conversations with Easton (for the tube) and several bearing manufacturers, the change was made. Pacific made the first bearings which were aluminum and coated with a ceramic bearing surface. Later, we sourced the bearings from IGUS as they were considerably less expensive. That's all I got from the mental archives! I also recall that the roller bearings didn't perform well when pre-loaded for thrust loads... and moving to tapered roller bearings proved to be quite expensive and heavy. Also, the tolerances required to axially lock everything in place on the roller bearings made for some absurd manufacturing specs that had the factory pushing back to open up the tolerances to make a simpler design. The bushings were much better suited to support the thrust loads, and the larger diameter distributed the bearing loads over a larger area which improved durability... also the rear triangle could compress a little bit to absorb manufacturing variations that control axially spacing so that during assembly you could squeeze things together and lock everything in nice an tight.

A lot of manufacturers were going to composite bushings during that time, and away from roller bearings... primarily to save weight and cost, but also to address corrosion concerns and better handle thrust loads (which only tapered roller bearings do well). We also felt that the hollow tube looked better... and conveyed a (real or perceived) sense that the larger bushing would result in less deflection and flex in the rear triangle. Funny thing is that we used roller bearings extensively on the straight six and subsequent DH designs precisely to eliminate stiction and to increase small bump responsiveness.

First generation small pivot Sweetspot.
Second generation large/hollow pivot Sweetspot.