You know, I looked at this topic a few years ago - for two reasons.
First, I was lucky enough to get my hands on a pair of NOS/NIB power window regulators for a PW/PL conversion I was doing. When I first looked at them, I was surprised to find that some of the rollers were essentially locked. It was awhile ago, so I can't remember if just one locked or just two. You could rotate it/them with a pair of Channelocks and a little bit of effort. But, I didn't want to FU a brand new pair of OEM regulators by cranking on the rollers - that weren't actually supposed to rotate on their pins.
Second, it made more sense to me that they were apparently designed to slide along - rather than actually roll - in the tracks. If you think about it, how much rotational force is actually imparted to a nylon roller that is applying a mainly upward/downward pressure - on the intentionally greased horizontal surfaces of the tracks.
I did a lot of research on the subject - or tried to anyway. Apparently, there isn't a lot of interest/info in this issue. But in the end, what little I did find lead me to believe that the term "roller" is a misnomer. A more accurate description might have been "slider".
There are really just two problems that can develop with these nylon pieces. For the sake of argument, let's just call them "wheels":
1. Flat spots on the OD’s of the wheels - this is blamed on the wheel hubs being unable to rotate on their pins (and one area getting worn down by abrasion after years of sliding along in the tracks).
2. Excessive play/increased clearance between the pin and wheel hub - this is blamed on years of rolling and the pressure created by lifting the glass (IOW, just normal wear & tear).
And here is the most frequent complaint associated with each of the two types of wheel problem.
1. The locked wheel/flat spot complaint: the window doesn't go all the way up. The conventional wisdom here is that as the depth of the flat spot increases, the distance between its pin and the upper surface of the wheel is decreased. That, in turn decreases the total vertical rise of the window. Eventually, it gets so worn - that when you close the window - the glass doesn't seal tightly up against the top edge of the run and you get an annoying whistle on the highway.
Sounds reasonable right? Until you realize - that even when the window is all the way up - there are still a few teeth left on the regulator's driven quadrant gear that don't get used by the pinion (hand crank or drive motor). There is way more than enough to compensate for any minor lost motion due to a flat spot.
2. The wobbly wheel complaint: This probably doesn't even warrant a description - we've probably all seen what loose rollers can do. Over time, they can get so loose on their pins that rolling the window up can become a real PITA.
The glass gets cocked in channel runs and jams – usually on the way up. If it is a manually operated regulator, the hand crank splines can get stripped - then you have to use Vise-grips. With PW’s, the motors often can't lift the glass. And even if they can lift it - they do it real slow. The motors fail prematurely. In the worst cases, the glass can fall right out of the runs.
I decided to leave my rollers tight on the pins - just like I found them out of the box. I never did find out how they were holding up because I only had the truck for about a year after installing them.
