"Allow you to run with very little clearance."
OK so it's hard to accept what I say about the importance of preloading a bearing, I get that. But here's what SKF says:
In applications where the bearing size is determined by factors other than load â€“ for example, shaft diameter constrained by critical speed â€“ the bearing may be lightly loaded in relation to its size and carrying capacity. Where there are very light loads, failure mechanisms other than fatigue, such as skidding and smearing of raceways or cage damage, often prevail. To provide satisfactory operation, rolling bearings must always be subjected to a given minimum load. As a general rule, minimum loads of 0,01 C should be imposed on ball bearings and 0,02 C on roller bearings. More accurate minimum load requirements are given in the product sections.The importance of applying a minimum load is greater in applications where there are rapid accelerations or rapid starts and stops
, and where speeds exceed 50% of the limiting speeds listed in the data tables (Speed limitations). If minimum load requirements cannot be met, potential improvements are:
Use a bearing with a smaller dimension series.
Consider special lubrication or running-in procedures.
Consider NoWear coated bearings.
Consider applying a preload.
Here's the link: https://www.skf.com/group/products/...cess/bearing-size/requisite-minimum-load
Nobody knows why Hele and company didn't pick up on this, I guess that decades of adjusting multiplate clutches with clearances so they wouldn't slip just couldn't be ignored.
Please note what SKF says about rapid starts and stops, which is what you get when the release bearing spins with the clutch and then decelerates when the pull rod is activated. (the pull rod doesn't spin, it sits still)
If preloaded it spins all the time with no abrupt starts and stops, and lasts forever, just like the other bearings in the engine and gearbox.
But then, to get a triple clutch to work it will already be preloaded by your cable adjustment. My point is that any clearance is neither required nor desirable.
By controlling the preload with the Belleville washer trick you avoid loading the bearing so much that you induce clutch slip.